PLATING BATH SOLUTIONS AND METHODS OF PLATING
20260098344 ยท 2026-04-09
Assignee
Inventors
Cpc classification
International classification
Abstract
Compositions for electroless plating baths and their use are disclosed, and more particularly chemical solutions and a method to transform a plating bath from the ability to produce one type of plated layer into a plating bath able to produce a different type of plated layer.
Claims
1. An electroless metalized bath for plating a plurality of types of articles, comprising one or more initial solutions mixed with water, said initial solutions comprising together, in defined proportions, at least one metal salt; at least one complexer, at least one reducing agent, at least one pH adjuster in addition to said at least one complexer; and at least one stabilizer for stabilizing a plating reaction; wherein said bath is controlled by maintaining bath pH and temperature; wherein in said plating bath, plating one or more articles with a first kind of plated layer having specific physical properties; wherein replenishing said plating bath by adding an additional amount of one or more solutions to said plating bath, said additional amount determined based on the determined depletion of at least one of said metal salt from said plating bath, plating at least one additional article with a plated layer having the same specific physical properties as said first kind of plated layer; wherein replenishing said plating bath by adding an amount of a different one or more solutions to said plating bath, said amount determined based on the determined depletion of at least one of said metal salts from said plating bath, and plating at least one additional article with a second kind of plated layer having different specific physical properties from said first kind of plated layer.
2. The method of claim 1, wherein said one or more solutions is limited to one.
3. The method of claim 1, wherein said initial one or more solutions is used to produce a high phosphorus kind of electroless nickel plated layer.
4. The method of claim 1, wherein said different one or more solutions is used to produce a medium phosphorus kind of electroless nickel plated layer.
5. The method of claim 2, wherein said different one or more solutions is used to produce a low phosphorus electroless kind of nickel plated layer.
6. A method for plating a plurality of types of articles comprising the steps of: formulating a plating bath by mixing one or more initial solutions with water, said initial solutions comprising together, in defined proportions, at least one metal salt; at least one complexer, at least one reducing agent, at least one PH adjuster in addition to said at least one complexer; and at least one stabilizer for stabilizing a plating reaction; controlling said bath by maintaining bath pH and temperature; in said plating bath, plating one or more articles with a first kind of plated layer having specific physical properties; replenishing said plating bath by adding an additional amount of one or more solutions to said plating bath, said additional amount determined based on the determined depletion of at least one of said metal salt from said plating bath, plating at least one additional article with a plated layer having the same specific physical properties as said first kind of plated layer; and replenishing said plating bath by adding an amount of a different one or more solutions to said plating bath, said amount determined based on the determined depletion of at least one of said metal salts from said plating bath, and plating at least one additional article with a second kind of plated layer having different specific physical properties from said first kind of plated layer.
7. The method of claim 6, wherein said one or more solutions is limited to one.
8. The method of claim 7, wherein said initial one or more solutions is used to produce a high phosphorus electroless nickel kind of plated layer.
9. The method of claim 7, wherein said different one or more solutions is used to produce a medium phosphorus kind of electroless nickel plated layer.
10. The method of claim 7, wherein said different one or more solutions is used to produce a low phosphorus kind of electroless nickel plated layer.
11. The method of claim 7, wherein said initial one or more solutions and said different one or more solutions comprise the same composition and defined proportions of at least one metal salt; at least one complexer, at least one reducing agent, at least one pH adjuster in addition to said at least one complexer.
12. The method of claim 6, wherein said initial one or more solutions and said different one or more solutions comprise different compositions and/or defined proportions of one or more stabilizers for stabilizing a plating reaction.
13. The method of claim 6, wherein said initial one or more solutions and said different one or more solutions comprise a different composition and/or defined proportions of one or more accelerators to accelerate a plating reaction.
14. The method of claim 6, wherein said at least one stabilizer is selected from the group consisting of lead, cadmium, bismuth, tin, copper, antimony, sulfur, and non-metal stabilizers in said initial one solution and/or said different one solution.
15. The method of claim 6, wherein said at least one stabilizer in said initial one or more solutions and said different one or more solutions are free from the group consisting of lead, cadmium, chromium, or any substances that would cause the plated layer from said plating bath to not conform to Restriction of Hazardous Substances Directive (RoHS), End of Life Vehicle Directive (ELV), and Waste Electrical and Electronic Equipment Directive (WEEE) regulations.
16. The method of claim 6, wherein said initial one or more solutions and said different one or more solutions are made without introducing PFAS substances.
17. The method of claim 6, wherein said plating bath is an electroless nickel plating bath with a concentration of 3 to 6 grams of nickel per liter of said plating bath.
18. The method of claim 6, wherein said plating bath further comprises a particulate material capable of producing a plated layer containing said particulate material.
19. The method of claim 6, wherein the life of said bath is extended upon introduction of said different one or more solutions.
20. The method of claim 6, wherein the pH of said initial one or more solutions and/or said different one or more solutions is within 3 pH units of the pH of said plating bath.
Description
DETAILED DESCRIPTION
[0077] The present invention is directed to both economic and environmental improvements in the plating industry in that the present invention extends the life of a plating bath. The novel approach of the present invention involved extending a bath's life by repurposing the bath for a different type of plating, where the extension occurs after some period of usage, at the end of the plating bath's useful life, or before reaching that point.
[0078] In the present invention, a plating bath is formulated for plating at one level of phosphorous and the same bath, when replenished at or near the end of its useful life (or even before), said bath is replenished with one or more solutions for a second purpose, without the removal of any portion of the bath and without regenerating the bath in any way.
[0079] In one embodiment of the present invention, a first single solution useful for both the makeup and replenishment of a plating bath is used, where the bath is useful and economical on a commercial basis, as well as to the solution's and the bath's use, and subsequently a second single solution, itself useful for both the makeup and replenishment of a plating bath is used for a different plating purpose. That is, one solution is used for makeup and replenishment for a first purpose and then a second solution is added for a second purpose, where the second solution is further used as a replenisher for the bath.
[0080] In another embodiment multiple solutions may be used for makeup for the first purpose, multiple solutions of a second type may be used for replenishment, then multiple solutions of a third type may be used for a second purpose.
[0081] The present invention serves to solve a problem which has vexed the industry for decades. By way of example, high phosphorous plating baths, required for plating in select applications, tend to have a very short life, on the order of 5 or fewer metal turnovers (MTOs) of an EN bath containing 6 grams per liter of nickel. Each formulated bath has expense and by having a bath with a short life, the overall expenses ramp up quickly. Further, the bath ultimately has to be disposed of and because of the chemical makeup of the bath, disposal can also be expensive and have an environmental impact. Benefits are clear if a bath's life can be extended. The present invention attempts to do so by re-purposing the bath to a less-than-high phosphorous bath to be used to plate applications not requiring a high phosphorous EN coating which the used bath is no longer able to produce in an effective, efficient, or economical way.
[0082] Though the present invention primarily focuses on electroless nickel phosphorus plating systems, other plating systems fall within the spirit and intent of this invention. Other relevant examples of systems and baths include, but are not limited to: [0083] All electroless plating baths [0084] All electroless nickel plating baths [0085] All nickel-phosphorous alloy ratios [0086] Electroless nickel-boron [0087] Poly alloys [0088] Electroless cobalt [0089] EN systems resulting in different levels of brightness [0090] EN plating that is subsequently blackened [0091] Non-metal stabilized plating systems [0092] Metal stabilized plating systems [0093] Heavy metal stabilized plating systems [0094] Composite plating systems [0095] Electroless copper, palladium, gold, and/or silver [0096] Alloys/combinations thereof
[0097] The solution of the present invention may contain some quantity of one or more of the materials that are ordinarily added to the plating bath as auxiliary solutions.
[0098] Although the present invention may include components for stability, brightness, fume control, pit reduction, or other alterations to the properties of the coatings, in some situations, platers may add additional auxiliary solutions to the plating bath for modified stability, brightness, fume control, pit reduction, or other alterations to the properties of the coatings resulting from the plating baths.
[0099] The present invention includes embodiments directed to similar practices and solutions used for electroless nickel phosphorous, nickel boron, nickel boron phosphorous, nickel tungsten phosphorous, cobalt boron, cobalt phosphorous, copper phosphorous, and other types of plating baths.
[0100] Typically, the plater (the end user of the plating bath) buys the solutions needed to make up and replenish the plating baths from a supplier (a manufacturer or distributor) of such solutions.
[0101] When such solutions with pH levels different than the pH level of the plating bath are added to a plating bath, there is an inherent acid-base reaction. That acid base reaction can cause a precipitation of materials such as nickel hydroxide or other precipitates in the plating bath. Such precipitation is known to cause defects in the plated layer, such as roughness, pitting, reduced brightness, lower corrosion resistance, and other defects. This precipitation also includes degeneration of at least some or all of the bath components in advance of subsequent plating.
[0102] This phenomenon is amplified by the greater the difference between the pH of the solution(s) and the pH of the plating bath.
[0103] The importance of pH compatibility between the plating bath and any solutions or materials added to the plating bath is amplified by the elevated temperature of the plating bath. At such temperatures, the volatile reaction of components containing alkaline materials such as but not limited to ammonia and other hydroxides or carbonates and the like are problematic to the worker who is tasked with making such replenishments to the plating bath. As the task is not pleasant from an odor, safety, and other reasons, having a single solution with a pH compatible with the plating bath is desirable.
[0104] For the reasons disclosed herein, the compatibility of the pH of the solution to the plating bath of the present invention is advantageous in the industry. It is desirable that the pH of the solution be similar to that of the plating bath during operation, such as but not limited to within 3 pH of one another. It is desirable that the pH of the solution be acidic if the plating bath is acidic. It is desirable that the pH of the solution is not more than three pH units different than the plating bath. Also, during operation of the bath, certain characteristics of the bath might be regularly measured, such as but not limited to temperature, pH, and metal content or density.
[0105] As will become evident in the examples below, the present invention includes multiple combinations of ingredients in various ranges of quantities/percentages in a single solution useful to both makeup and maintain the composition of ingredients in the plating bath. In general, the present invention is comprised of a family of solutions each of which affords an improved ease of use and also extends the life of typical plating baths.
[0106] Single component electroless nickel plating systems overcome a number of factors which have limited manufacturers and users of plating baths to use plating bath systems with multiple solutions instead of a single solution. These factors are disclosed in U.S. Pat. Nos. 10,006,126, 10,731,257, and 10,731,258, which are incorporated herein by reference.
[0107] A key measure of the quality and suitability of solutions for making up and replenishing electroless plating baths is the resulting plating rate and lifetime of the plating bath.
[0108] The plating rate corresponds to the thickness of the coating achieved from a plating bath over a period of time. For example, microns of thickness per hour is a typical measure of plating rate. There are generally accepted ranges of plating rates for various types of plating baths and these rates might differ based on the quantity and/or types of articles being plated. For example, a typical low to medium phosphorous plating bath typically plates at a rate of 15 to 25 microns per hour. A typical high phosphorous electroless nickel plating bath plates at a rate of 7 to 12 microns per hour. The plating rate of a given plating bath depends upon operating temperature, bath loading, pH, agitation, age of the bath, and other factors. The choice of type of phosphorous also depends on a variety of factors, including particularly the articles being plated and the purpose of the plating.
[0109] A bath life is typically measured in metal turn-overs, or MTOs. Different baths can have different MTO lifetimes depending on a number of factors such as but not limited to the type of plating bath, the operation and maintenance of the plating bath, the quantity and types of articles plated, the base metal of the articles being plated, and other factors. One MTO represents the use of a plating bath over a period of time where parts are plated, the cumulative quantity of the metal salt in the bath at makeup is used (deposited onto parts immersed in the plating bath) and replenished into the plating bath. For example, if a one-liter electroless nickel plating bath is made up with 6 grams of nickel metal (coming from a metal salt like nickel sulfate), parts are plated therein until 0.6 grams of nickel are depleted, the bath is replenished with 0.6 grams of nickel, and this process is repeated 9 more times for a total depletion and replenishment of 6 grams of nickel, then this bath has achieved one MTO. Of course, it is not only the nickel salt that is consumed and replenished in the course of usage. Any and all reducing agent(s), stabilizer(s), brightener(s), and all other ingredients must be maintained in proper concentration in the plating bath, otherwise plating bath performance, life, and resulting plating quality will suffer. Adding too much or too little of certain ingredients can also reduce the bath life. Another factor influencing the bath life is the gradual buildup of byproducts in the plating bath as a result of the plating reaction. A maximum bath life is important to the plater since the solutions used for plating baths are a significant cost to the plater; it is time consuming, inconvenient, and costly for the plater to dispose of a used bath and replace it with a new bath; treatment of a used bath is costly and can have environmental implications. Therefore, it is important to the plater that the solutions used for bath makeup and replenishment are formulated in a way as to maximize bath life and performance, where a measure of bath life is the number of MTOs.
[0110] When evaluating solutions for the makeup and replenishment of an electroless plating bath, achieving at least one MTO with proper performance and results is a significant threshold to validate the composition(s) of the solution(s). Although some plating bath systems exist for the perpetual use of the plating bath, accomplished by removal of byproducts from the bath and replenishment with select materials, such baths are generally not considered practical nor economical for widespread commercial use, and therefore the life of an electroless plating bath in terms of the number of MTOs achievable is an important factor in the utility of an electroless plating bath. Further, in the industry these types of baths are referred to as regenerative and not replenishable baths.
[0111] Generally speaking, the number of MTOs for a bath is limited by the chemical composition of the bath as one important factor. For example, and significant to this invention, a commercial high phosphorous bath is limited to around 5 MTOs, whereas a medium phosphorous bath can achieve more MTOs. Of course, the performance requirements of the objects to be plated dictate whether a bath is high, medium, or low phosphorous.
[0112] As plating baths are used to plate articles and the baths increase in the number of metal turnovers, ultimately the bath reaches a point where, because of byproduct accumulation, the bath must be disposed of. This disposal is typically further due to the buildup of contaminants in the plating bath. These contaminants can include byproducts of the plating reaction such as sodium orthoposphite in the case of electroless nickel, other material build-up such as a zincate solution introduced to the plating bath from the pretreatment of aluminum articles prior to plating, or other contaminants from the chemical process such as the drag-in from articles immersed into the plating bath, and even material in the plating shop that can otherwise migrate into the plating bath.
[0113] As such materials build-up in the plating bath, they can cause deleterious effects to both the bath and the plating including but not limited to a reduced plating rate and/or quality problems with the plated deposit such as poor adhesion, pitting, roughness, lack of uniformity, altered physical properties, and other defects.
[0114] Therefore, plating baths are normally disposed of at a certain number of metal turnovers before the plating becomes poor. One reason for this commercial practice is that metal turnovers are easier to measure than the cumulative amount of known or unknown contamination. Moreover, it is general practice in the plating industry to try and dispose of a plating bath just before costly quality problems occur on the articles being plated. For example, if a plating shop anticipates adhesion problems on the plating on aluminum articles from a plating at around four to seven metal turnovers due to the buildup contamination of zinc in the plating bath from the pretreatment process of plating on aluminum, the plating shop may discard a plating bath at three metal turnovers to avoid such potential problems and then makeup a new plating bath.
[0115] There is a method, known as bleed and feed that is rarely if ever practiced in advance of the present invention and not practiced commercially. In this method, as a plating bath reaches a certain number of metal turnovers, a portion of the bath is removed, that portion is replaced with a newly formed plating bath and mixed into the unremoved portion of the bath. In other words, some of the byproducts together with some of the other elements in the bath are removed as a vehicle to extend the bath's life. This method effectively dilutes the plating bath with new plating bath and thereby reduces the concentration of contaminants in the plating bath so the plating bath can continue to be used to plate articles with consistent performance and plating results. Of course, it also requires disposal of useful but unused chemicals as well. For example, if a plating bath were made up and used to a total of four metal turnovers and then 25% the plating bath was removed and replaced with a newly made-up plating bath, the resulting plating bath would effectively be at 3 metal turnovers in terms of bath age and the amount of contamination. The benefits of such a method are that a plating bath can be used at a more steady-state in terms of parameters (such as plating rate, stability, temperature, pH, etc.) and plating quality (such as adhesion, corrosion resistance, stress, color, quality, etc.).
[0116] Despite these benefits, the bleed and feed method are rarely if ever practiced commercially. There are a number of reasons for this lack of commercial acceptance. These include the additional cost of materials as traditionally the cost to makeup new bath with multiple components is greater than the cost to replenish an existing bath. There is the added time and labor cost to perform the bleed and feed process, especially with multiple components needed to make up the new portion of the bath. In addition, the bleed and feed process may result in more waste for disposal, as well as more frequent disposals of materials.
[0117] Single component electroless nickel solutions make a version of the bleed and feed method commercially viable and advantageous. As an example below demonstrates, the novel utility of a single solution for both the makeup and replenishment of a plating bath solves this problem. As a single solution for both the makeup and replenishment of a plating bath, this enables a plating shop to perform the bleed and feed method using fewer chemicals, or less of various chemicals, that is cheaper, easier, faster than it would be with a multiple solution system. The plating shop is able to bleed a portion of the plating bath and either 1) replace this portion with the same volume of a newly made-up plating bath or 2) replace this portion with just the required amount of the single solution of a present invention and dilute the plating bath up to the operating volume. This second option, facilitated by the present invention, is essentially just a large replenishment to the plating bath which is made practical by the use of a single solution for its simplicity and compatibility with the plating bath for the reasons explained in this disclosure.
[0118] It is important to note the difference between extending the life of a plating bath in terms of time versus extending the life of a plating bath in terms of MTOs or metal turnovers. The present invention extends the number of MTOs obtainable from a plating bath.
[0119] The present invention provides utility to a plating shop where zinc build up in the plating bath from plating on aluminum substrates is problematic. Prior to the present invention, a plating shop's ability to use a plating bath beyond the point when the zinc concentration reaches a level at which plating additional aluminum substrates would be impossible depended on the plating shop's ability to plate on substrates made of materials other than aluminum such as steel, stainless steel, copper alloys, and others that do not go through a zincate type of pretreatment and therefore do not introduce zinc to the plating bath. Prior to the present invention, a plating shop may be able to do this only if they have parts made of a material other than aluminum that require the same type of plating as the plating applied to the aluminum parts. This is because the additional non-aluminum parts can be plated in the plating bath without further increasing the zinc concentration in the plating bath and not subject to the adhesion problems that would be inherent in plating onto additional aluminum substrates. By using the present invention, a plating shop may have additional opportunities to continue to use the same plating bath on parts other than aluminum by changing the plating bath to produce a different type of coating which may be more useable on these non-aluminum parts.
[0120] It is also demonstrated in the examples of the present invention that the modification of a plating bath from one purpose to another purpose can include modifying the pH of an electroless nickel plating bath, say from acid to alkaline, or from alkaline to acid. Whereas the vast majority of electroless nickel plating baths are operated at acidic pH levels, some electroless nickel plating baths are operated at alkaline pH levels. Such alkaline electroless nickel plating baths are used in the plating of aluminum substrates. As described above, the process of plating aluminum substrates leads to the buildup of zinc in the plating bath. By using an alkaline electroless nickel plating bath for a thin strike or flash layer before transferring the substrate into an acid electroless nickel plating bath for the full plated layer, the zinc is contained in the alkaline bath instead of the acid bath. The alkaline bath has a higher tolerance to zinc contamination. This dual plating bath process of an alkaline bath before the acid bath, extends the life of the acid plating bath. By using the present invention to be able to convert a plating bath from acid to alkaline, or alkaline to acid, the plating shop is able to optimize the utility and lifetime of one or more plating baths; as they can decide when a plating bath has reached the end of its useful life for one purpose, but then repurpose the plating bath so it can be used for another purpose that may still be possible.
[0121] In summary, the present invention introduces multiple plating processes all directed to extending bath life and resulting in a plurality of coating compositions and/or plating a plurality of objects. Some embodiments utilize a single solution for makeup and replenishment followed by a second solution for plating a second type of object (or resulting in a somewhat different coating). Some solutions serve the same effect but are not single solutions. Other embodiments include an interim step of removing a portion of the bath after a determined amount of time or plating before adding solution to create at least a second coating type or plating at least a second type of object.
[0122] When evaluating solutions for the make-up and replenishment of an electroless plating bath, verification of the physical properties of the coatings resulting from this plating bath is significant to validate the composition(s) of the solution(s). Such physical properties of the coatings include, but are not limited to, composition, hardness, corrosion resistance, thickness, uniformity, electrical conductivity and resistivity, porosity, appearance, brightness, reflectivity, adhesion, stress, elasticity, tensile strength, elongation, density, coefficient of thermal expansion, wear resistance, coefficient of friction, and/or other properties.
[0123] In U.S. Pat. No. 5,609,767 (Eisenmann) Eisenmann discloses an experimental rejuvenation type of plating bath which is different than the replenishment type of plating bath for the present invention, but Eisenmann is directed to plating only one type of object or one type of coating.
[0124] The present invention uses multiple solutions to, in some embodiments, extend the life of a plating bath by changing the purpose of the plating bath by enabling the plating bath to produce more than one type of coating during its overall lifetime. Eisenmann, by contrast, uses equipment and non-plating processes to extend the life of a plating bath through rejuvenation to remove byproducts in the plating bath so the plating bath can be used, potentially for an infinite lifetime to produce a same one type of coating over the course of the entire lifetime of the plating bath.
[0125] The present invention is directed to electroless plating baths that are made-up and replenished over the course of the plating bath's lifetime without rejuvenation or other methods of extracting byproducts from the plating bath with the intention of such extraction and subsequent chemical additions to extend the life of the plating bath. Rejuvenation processes in the EN plating industry are exceptionally rare. Nearly all EN plating in the world is by a replenishment method, not with rejuvenation. The goal, method, and chemical formulations used for such rejuvenation type plating systems as well as the extensive equipment that is required to enact the rejuvenation process is substantially different than the vastly more commonly used replenishment type plating baths in the plating industry. Whereas the present invention is, in part, directed to extending the life of an electroless plating bath, the present invention is not a rejuvenation type process. The present invention is not intended to remove byproducts from the plating bath nor provide for a plating bath with an essentially endless life as is the objective of rejuvenation type processes.
[0126] products from the plating bath nor provide for a plating bath with an essentially endless life as is the objective of rejuvenation type processes.
[0127] Once the bath has been prepared, it is ready for use in the electroless plating process of the present invention. This involves contacting the surface of an article to be plated or coated with the electroless metallizing bath. However, the article to be coated may require preliminary preparation prior to this contact in order to enable the autocatalytic plating deposition on the surface of the article. This preparation includes the removal of surface contaminants. For example, this process may involve any of, but not limited to, degreasing, alkaline cleaning, electrocleaning, zincating, water or solvent rinsing, acid activation, pickling, ultrasonic cleaning, physical modification of the surface, vapor or spray treatments, etc.
[0128] An electroless plating bath is typically operated generally according to the following practices related to the equipment, and operation of the bath. [0129] The plating tank is typically constructed of polypropylene, stainless steel (Type 316) or mild steel with a suitable tank liner depending on bath in use and other considerations. Stainless steel tanks may be anodically protected. [0130] Filtration through a 10-micron or finer rated polypropylene filter bag system is suggested. Polypropylene wound cartridge filters are also permissible, but generally are not as easy to use as filter bags. The filtering pump system should turn the bath over at a rate of at least 10 times per hour. [0131] Agitation is useful in maintaining bath homogeneity and for providing a consistent finish for the coating. Air spargers with air from a high volume, low-pressure air blower is recommended. Compressed air is not recommended due to potential oil contamination. Other types of agitation, may also be used. [0132] Heating of the bath may be accomplished by various methods including heat exchangers and immersion heaters. The bath temperature should be monitored and maintained closely. [0133] Cooling of the bath with an appropriate cooling apparatus should be done rapidly at the end of a shift or any time the bath will not be used for an extended period of time. [0134] Rack, barrel, and fixturing devices are typically constructed of compatible materials such as polypropylene, chlorinated polyvinyl chloride (CPVC), stainless steel, PTFE, Viton, silicone rubber, and others that can withstand the chemicals and temperature of the plating bath and pretreatment process. Maskants may be used to protect fixtures from being plated. [0135] Masking is typically accomplished with compatible materials such as certain vinyl tapes, stop-off paints, plugs and gaskets made of Viton, silicone rubber, and others that can withstand the chemicals and temperature of the plating bath and pretreatment process. [0136] The plating tank should be clean and passivated. The most common method is with a solution of 40-50% nitric acid for 2-3 hours at room temperature, followed by rigorous rinsing and neutralizing of the tank and verification that no nitrate contamination remains. [0137] The plating bath is typically maintained to be within 80% and 100% concentration of nickel, hypophosphite, stabilizers, or other chemicals based on the initial makeup concentration of these ingredients. Tighter control further helps performance. [0138] Titration of the plating bath is typically before and after every batch of parts that is plated. Replenishing is normally done during plating cycles if the workload will lower the nickel concentration to 90% or less for optimal bath performance and plating quality. [0139] Continual and accurate measurement of bath temperature, pH, and bath solution level is important and typically done. Evaporation will reduce bath volume and give false indication of actual concentration. Adding DI water as needed during the plating cycle is useful to keep solution at proper level. [0140] The deposition rate of a given plating bath depends upon operating temperature, bath loading, pH, agitation, age of the bath, and other factors.
[0141] Although the examples detailed below depict specific combinations of components, time, and control, the reader should recognize that the present invention is not limited to the specific materials and metrics in the examples. For example, plating different goods may require different quantities or combinations. The pH of the plating bath can vary by application but is preferably in a range of 4.0 to 9.0. The plating bath temperatures can preferably be in the range of 20 to 100 degrees Celsius. The duration of the cycle times can be in any range required to provide the coating thickness and properties desired.
[0142] The solution of the present invention's contents may vary based on the plating needs, such as but not limited to, the type of plating necessary, and the types of objects being plated. Preferably, the solution is directed to electroless nickel plating, but other types of plating may also lend themselves to a single solution, such as but not limited to other types of electroless nickel plating.
[0143] In U.S. Pat. No. 10,006,126, among many other prior art references in the field of electroless nickel plating, plating baths and processes are limited to a plating bath of a singularly defined type that produced a coating of a singularly defined type for the lifetime of the plating bath. For example, a high phosphorus plating bath would be made-up, articles would be coated in said plating bath with a high phosphorous electroless nickel plated layer, and the plating bath would be replenished with one or more components designed to produce a similar and consistent high phosphorus coating until the end of the plating bath's useful lifetime. This lifetime in the number of metal turnovers or MTOs that the plating bath is able to achieve before it is no longer physically or commercially viable to continue the use of this plating bath, as described herein.
[0144] Such end of bath life causes can include an unacceptably slow plating rate of the plating bath; or unacceptable properties of the coating itself such as undesirable hardness, phosphorus content, corrosion resistance, stress, physical appearance, and other properties.
[0145] The present invention instead teaches a method and plating bath whereby a plating bath is: [0146] 1) made-up with one or more chemical solutions and ingredients to produce a first coating of a specific one or more physical parameters, [0147] 2) articles are coated with said first specific physical parameters characteristics, [0148] 3) the plating bath is replenished with one or more chemical solutions and ingredients in order to continue to produce the same first specific physical parameters of the coating on additional articles from said plating bath, and then [0149] 4) the bath is subsequently replenished with a different (second) one or more chemical solutions and ingredients in order to produce a different one or more physical parameters of the coating on additional articles plated in the same plating bath.
[0150] Said another way, a first bath for a first purpose is used and subsequently refunctioned for a second purpose merely be adding a second combination of chemical solutions, thereby extending the overall life off the bath.
[0151] The benefits of the present invention include, but are not limited to, methods whereby: [0152] 1) Multiple types of coatings may be produced from the same plating bath, [0153] 2) A plating bath's life can be extended so as to improve utilization of components and extend the lifetime the plating bath, and [0154] 3) Reducing the amount of waste generated from plating.
[0155] Extending the lifetime of a plating bath is of great interest for commercial, profitability, productivity, waste reduction, convenience, and other benefits to the day-to-day operation of one or more planting baths in a plating shop. While there are many ways in which users of plating baths routinely work to extend the lifetime or MTO's of plating baths, but these methods differ from the present invention's multi-purpose function. Such methods include, but are not limited to: [0156] 1. Insuring proper maintenance of the chemical ingredients in the plating bath through accurate replenishment of the plating bath, [0157] 2. Utilizing a single component replenishment solution instead of multiple components to enable the ingredients in the plating bath to stay within a defined range and ratio with the other ingredients, [0158] 3. Avoiding contamination of the plating bath, [0159] 4. Diligent maintenance of the plating tank and equipment, [0160] 5. Avoiding defects in the coating of articles that would necessitate reworking of the articles and therefore additional redundant usage of the plating bath and reduction of its lifetime, [0161] 6. Cooling heated plating baths at the end of a work shift, [0162] 7. Filtration of the plating baths to avoid particulate that could lead to excessive plating within the plating bath and or the tank and equipment within the plating tank, [0163] 8. As well as many other methods within commercial use.
[0164] One example of a benefit of the present invention in extending the lifetime of a plating bath is due to the difference in lifetime typically achieved in electroless nickel phosphorus plating baths based on the type of plating bath being used. High phosphorous electroless nickel plating baths are generally understood in the plating to industry to be useful for a lifetime of approximately 4-6 mental turnovers before the plating bath has reached the end of its useful life. This range of MTOs is based on an EN plating bath having 6 grams per liter of nickel. Plating baths with less than 6 grams per liter of nickel can achieve a higher number of MTOs because less nickel and other chemical ingredients are needed to achieve each MTO. The amount of plating produced from a plating bath (measured in terms of grams of metal deposited and/or mil-square feet) depends on both the number of MTO's and the concentration of metal(s) in the plating bath. One reason for the end of the high phosphorus plating bath's useful lifetime between 4-6 metal turnovers is because by that time in the life of a high phosphorus electroless nickel plating bath, the plating rate becomes significantly slower than the initial plating rate of the plating bath when it was newly made-up, at least in part consequential to the existence of byproducts at a growing rate, and that the plating rate at 4-6 MTOs becomes slower than commercially desirable. A second important reason why plating shops will stop using a high phosphorous electroless nickel plating bat at around 4-6 MTOs is because the nickel phosphorus alloy coating achieved from a plating bath at that late stage in that the plating bath's life will no longer have the optimal physical properties required for commercial applications. For example, at that point in a high phosphorus plating bath's life, the coating will have different levels of hardness, stress, corrosion resistance, and other properties, compared to the levels of these parameters produced by the same plating bath when it was initially made up and/or had less MTOs. Consequently, at that point in the bath's life, the high phosphorous bath is no longer adequate for commercial plating.
[0165] Inadequate corrosion resistance of the plating from such a plating bath at this late stage of the bath's lifetime is significant because high levels of corrosion resistance are one of the primary reasons that a high phosphorus nickel alloy would be specified for a commercial application, and therefore why a high phosphorus type electroless nickel plating bath is used instead of using a low or medium phosphorus electroless nickel plating bath.
[0166] There are many reasons why a plating shop would prefer to use a low or medium phosphorous electroless nickel plating bath, rather than a high phosphorous electroless nickel plating bath. One such reason is the inherently faster plating rate of low and medium phosphorous electroless nickel plating baths compared to high phosphorous baths.
[0167] There are two most common methods used in the plating industry to test the corrosion resistance of plated layers, other than use of plated parts in actual usage conditions.
[0168] The first is a salt spray test where the plated part is enclosed in a chamber with a continual spray of a salt fog at defined temperature, humidity and salt concentration for a number of hours to determine the salt spray corrosion resistance of the coating. There are many flaws with this method as successful salt spray resistance depends on not only the plating, but also the substrate, the pretreatment of the substrate prior to plating, as well as the plating bath chemistry and how it is operated. Moreover, salt spray testing is a method to indicate the corrosion resistance of a plated layer, but this method generally does not represent the actual environmental conditions to which an actual plated part will be used in its actual application.
[0169] The second method to test the corrosion resistance of a plated layer is commonly known as the nitric acid test. The standard way this test is employed is to immerse a plated panel into concentrated nitric acid to see if there is any discoloration (corrosion) of the plating. A plated layer is considered to pass the nitric acid test if the plating can withstand 30 seconds of immersion in this nitric acid without discoloring. The nitric acid test is commonly used in the plating industry as test of corrosion resistance, which is also a verification of the percentage of phosphorous in an electroless nickel coating. In general, a high phosphorous electroless nickel coating will pass the nitric acid test. Low and medium phosphorous electroless nickel coatings will not.
[0170] A high phosphorus electroless nickel plating bath typically plates at a rate of 10 to 12 microns per hour at the outset of a new plating bath's life as made-up, and this rate typically gradually decreases to about 7 to 9 microns per hour after a number of metal turnovers.
[0171] By contrast, a typical medium phosphorus electroless nickel plating bath will have an initial plating rate between 18 and 25 microns per hour. As a typical medium phosphorus plating bath is used, the plating rate will normally decrease to about 15 microns per hour by the time the plating bath reaches eight or more metal turnovers.
[0172] A typical low phosphorus electroless nickel plating bath will have an initial plating rate between 20 and 25 microns per hour. As a typical low phosphorus plating bath is used, the plating rate will normally decrease to about 15 microns per hour by the time the plating bath reaches eight or more metal turnovers.
[0173] Users of such plating baths are able to counteract the inherent decrease in plating rate over the lifetime of a plating bath by adjusting parameters such as pH and temperature of the plating bath. However, these adjustments are only able to decrease the plating rate to a limited extent. Moreover, such adjustments may have consequences for the operation of the plating bath that are undesirable such as less stability of the plating bath, plate out onto the tank and auxiliary equipment, and so on. Plate out is a term used to describe the plating onto the tank, a tank liner if used, any auxiliary equipment in the plating tank such as pumps, pipes, and so on. Plate out is problematic for a number of reasons including the waste of chemicals used in plating these surfaces that are not desired to be coated, reducing the stability of the plating bath, affecting the plating quality on the coating on actual parts or substrates where quality coating is desired, the need to strip the plating from the tank, pumps, pipes and other auxiliary plated out surfaces, interruption of the plating schedule, reduction in plating bath life, additional waste treatment, and other problems known in the plating industry associated with plate out.
[0174] The percentage of phosphorus in the electroless nickel coating inversely correlates directly to the plating rate of the plating bath. As noted, the plating rate of high phosphorus electroless nickel plating baths is inherently slower than the plating rate of medium phosphorus or low phosphorus plating baths. The slow plating rate of high phosphorus plating bath is one of the key ways that high phosphorus plating baths are able to produce high phosphorus coatings.
[0175] The percent phosphorus in an electroless nickel coating can be adjusted to some extent in any type of plating bath (low, medium, or high phosphorus) by adjusting parameters such as the temperature, pH, plating bath age, surface area loading in the tank, agitation, and other factors. Practically, however, the amount of phosphorus in the electroless nickel coating that can be modified by adjusting these plating bath parameters is relatively small (essentially only by a few percent of phosphorus in the coating). Adjusting these parameters would not, for example, be able to convert what is typically understood to be a low phosphorus electroless nickel plating bath for example into a high phosphorus electroless nickel plating bath, similarly just by changing these parameters; it is not practical that a high phosphorus plating bath could be adjusted in order to produce a low phosphorus electroless nickel coating.
[0176] One of the reasons for this limitation is that high phosphorus plating baths used commercially in the planting industry are typically made without certain stabilizers and without sulfur ingredients, which can act as accelerators of the plating rate. Such sulfur based and other plating rate accelerating ingredients are commonly used in low and medium phosphorus electroless nickel plating baths. It is well known in the industry that cross contamination between low or medium phosphorous electroless nickel plating baths must be avoided into high phosphorus electrochemical plating baths. If the sulfur, or other ingredients contained in the low or medium high phosphorus bath, is allowed to contaminate the high phosphorus plating bath, sulfur and the like can impact the physical properties of the coating made by the high phosphorus electroless nickel plating bath. This impact can include the corrosion resistance of the coating which is especially problematic for the reasons noted herein that high corrosion resistance is one of the primary reasons for using a high phosphorus electroless nickel plating bath.
[0177] Manufacturers of electroless nickel plating solutions must also be careful to avoid sulfur and other ingredients from contaminating the plating solutions that are used in high phosphorus electroless nickel plating applications.
[0178] Extending the life of a plating bath is an important environmental consideration to avoid or delay wasting a plating bath before it is absolutely necessary to do so and then environmentally treat a plating bath. Waste treatment of a plating bath requires materials, energy, expense, labor, overhead, documentation and many other costs, so it is desirable to minimize the amount or frequency of plating baths that need to be waste treated. When a plating bath reaches the point that it is no longer considered commercially or technically useful for continued use, and therefore has reached the end of its useful lifetime, the plating bath is typically called used, spent, waste, or other such terms. These terms can be used interchangeably. Depending on location used, EN baths may or may not be considered hazardous waste according to regulatory agencies.
[0179] Waste treatment of spent electroless nickel plating baths is typically handled in the electroless nickel plating industry by one of several different methods. One method is to have the plating bath hauled away for treatment or disposal elsewhere. This method requires paying one or more third parties to remove and treat or dispose of the used plating bath in consistency with applicable regulations, among other reasons. Depending on the quantity of such used plating baths generated by a plating shop and depending on the location of the plating shop and the regulatory requirements of that locale, there may be permitting and other regulatory administrative requirements the plating shop would need to comply with. This is another possible expense of time and resources for the plating shop and therefore another reason why extending the plating bath lifetime would be advantageous.
[0180] A second method for treating a spent electroless nickel plating bath is to perform a procedure generally known as plateout. In this procedure, certain chemicals are added to the plating bath such as a pH adjuster to increase the pH of the plating bath, and/or such as additional reducing agent to the plating bath in order to increase the activity level of the plating bath. This is done so that when a load of parts, typically steel, or steel wool with a high surface area is immersed in the plating bath, the plating activity is so high that essentially all of the nickel metal in the plating bath will be plated out onto the steel or the like. This method is intended to remove the nickel from the plating bath, so that the remaining liquid of the plating bath will free or essentially free of nickel. Thus, the remaining liquid may then be treated separately by other methods such as ion exchange, precipitation, neutralization, reverse osmosis, or dilution with other waste streams in order to dispose of it. There are regulatory issues involved with this method as well.
[0181] A third method of treating a spent electroless nickel plating baths is to evaporate the plating bath. Naturally this takes time, energy, equipment, and disposal of the resulting dry material or sludge which also must be dealt with. Regulatory issues are also involved with this method.
[0182] Fourth, there are methods to chemically treat a spent electroless nickel plating bath that involve adding chemicals such as flocculants or absorbents to precipitate or otherwise separate the nickel from the plating bath. Such a precipitation method, like the plateout method, is often complicated by certain ingredients within a typical electroless nickel plating bath such as ammonium hydroxide and other complexing agents that are included in the plating bath for plating functionality, but complicate the ability to then remove the nickel from the plating bath. While such a precipitation method is able to be accomplished on a spent electroless nickel plating bath, and the nickel is entirely or essentially removed, the remaining liquid of the plating bath still needs to be treated by one or more of the methods noted above, in addition to still dealing with regulatory issues.
[0183] The present invention is a significant deviation from the prior art where the objective of the prior art plating solutions was to maintain a consistent type of coating over the entire course of the plating bath's lifetime. The present invention represents a novel method of using a plating bath to produce coatings of a specific type and then being able to continue to use the same initial plating bath that has been used for plating to produce coatings of a first specific type to then be able to produce coatings of a second specific, or different, type or kind. This is achieved in the present invention by using one or more chemicals or solutions in the initial phase of a plating bath's lifetime; and then at a point in time in the plating bath's lifetime, preferably but not exclusively at or near the bath's end of life, the plating bath is replenished with one or more chemicals or solutions that are different to some extent from the chemicals or solutions used in the plating bath in the initial phase of the plating bath's lifetime, thereby extending the bath's life beyond its nominal end of life.
[0184] One of the many practical advantages of the present invention relates to the issues disclosed above, and widely understood in the worldwide electroless nickel plating industry, is about overcoming the significantly shorter bath life achievable from a high phosphorus electroless nickel plating bath compared to the bath life achievable from a low or medium phosphorus electroless nickel plating bath. This significant difference in plating baths'lifetimes is widely understood and widely accepted in the electroless nickel plating industry. People knowledgeable about the electroless nickel plating industry understand why this differential in plating bath lifetimes makes high phosphorus electroless nickel plating more expensive, more wasteful, less productive, and with other inherent comparative deficiencies.
[0185] The practice prior to the present invention in the electroless nickel industry was to operate high phosphorus plating baths up to a lifetime of approximately 4-6 metal turnovers before resorting to waste treatment of the plating bath by the methods described herein or others that may be available to the plating shop. The present invention provides an opportunity to obtain further useful productive plating from such a plating bath that would have previously been considered spent or waste or no longer commercially useful. In one embodiment of the present invention, the present invention achieves this important benefit by replenishing a fully or partially used high phosphorus electroless nickel plating bath with one or more chemicals or solutions that are able to essentially transform the planting bath into a medium phosphorus electroless nickel plating bath. By doing so, the plating bath does not need to be removed from use and waste treated prematurely. Instead, the plating bath is able to continue to be used productively by producing a medium phosphorus electroless nickel alloy coating for additional metal turnovers of the plating bath and at a higher plating rate than the plating bath was providing during its initial period of use as a high phosphorus electroless nickel plating bath.
[0186] As demonstrated in the examples of the present invention, the transformation of the high phosphorus plating bath to a medium phosphorus plating bath drastically increases the lifetime of the plating bath and reduced the amount of waste required for treatment.
[0187] The plating bath in Example 1 was able to produce more than 5 additional MTOs of medium phosphorous EN plating after the same bath had already been used for 5.06 MTOs of high phosphorous plating. This achievement of the present invention cut the waste treatment of this bath by more than half.
[0188] As also demonstrated in the examples of the present invention, such as Example 2, the utility of the present invention is greatly enabled by the use of chemicals or solutions in each the multiple phases of the plating bath's lifetime where these chemicals or solutions are compatible with each other. This is especially true when the chemicals or solutions used in each of the multiple phases of the plating bath lifetime are as identical to each other as possible, other than, for example, the phosphorous levels and related chemicals.
[0189] Moreover, the utility of the present invention is also greatly enabled by the use of single component solutions in each of the phases of the plating bath's lifetime, as this provides the benefits inherent in the use of single component plating solutions as described herein, such as Examples 1, 2, 4, 6, 7, 8, 9, and 10.
[0190] For example, the transformation from the high phosphorus stage of a plating bath's lifetime to a medium phosphorus plating bath is facilitated when a high phosphorous single component electroless nickel solution is used for the initial bath makeup and subsequent replenishment in the first stage of its lifetime to produce high phosphorus electroless nickel coatings; and then when a medium phosphorous single component electroless nickel solution is used to replenish the bath in the second stage of its lifetime to produce medium phosphorus electroless nickel coatings is as close to identical as possible with the high phosphorous single component solution used in the first phase of the bath's lifetime. This is achievable when the two single component solutions have identical types and concentrations of the bulk ingredients such as metal salt, reducing agent, pH adjusters, complexing agents, and others as in Examples 1, 2, 6, 7, 8, 9, and 10.
[0191] These bulk ingredients represent typically more than 95% of the composition of a single component solution. When the only difference between the replenishment solution in the first stage of the plating bath's life and the replenishment solution in the second stage of the plating bath's life is the type or concentration of stabilizers, accelerators, brighteners, particulate matter stabilizers, and the like, then the effectiveness of transforming the plating bath from a plating bath capable of producing one type of plated layer to a plating bath capable of producing a different type of plated layer is dramatically increased. This improvement includes the effectiveness of transforming the plating bath from a high phosphorus planting bath to a medium phosphorus plating bath mid-use is dramatically increased.
[0192] Maximum consistency in the chemicals or solutions used in the multiple phases of a plating bath's lifetime in the present invention is also important not only for the performance of the plating bath, but also the physical characteristics of the resulting plating onto articles. The plating itself must meet various requirements such as appearance, uniformity, level of brightness, and so on. The compatibility of the replenishment solution from the first phase of the plating bath life to the replenishment solution in the second phase of the plating bath life can significantly improve the ability of the plating bath in the second phase to produce coatings that meet the various physical properties required as has also been discussed herein.
[0193] The use of auxiliary chemicals to facilitate any or all aspects of the plating bath performance and or properties of the plated layers is certainly viable within the scope of the present invention. Such auxiliary chemicals maybe added to the plating bath in addition to the one or more premixed solutions as discussed in the present invention. Such auxiliary chemicals may also be added to the one or more premixed solutions for the purposes described herein.
[0194] In addition to the utility of producing different phosphorous concentrations in the electroless nickel plated alloy from a plating bath by employing the present invention, there are other properties such as but not limited to hardness, stress, magnetics, conductivity, resistivity, porosity, reflectivity, wear resistance, coefficient of friction, adhesion, elasticity, elongation, density, and coefficient of thermal expansion, that are important relative to the finished product and which can be varied in the different phases of use in a plating bath used according to the present invention. These and other properties differ at least between low, medium, and high phosphorus. Even changes in the brightness and aesthetic appearance of plating can be altered between different stages in a plating bath used according to the present invention.
[0195] It is important to point out that the present invention can also be used simply for extending the life of a plating bath even if changing one or more physical parameters of the coating from a first type to a second type of a plating bath life is not necessary. There is utility in extending a plating bath for the reasons disclosed herein.
[0196] The present invention can be practiced with one or multiple solutions for the makeup and/or replenishment of the plating bath in one phase of the plating bath's lifetime, and one or multiple other solutions for the replenishment of the plating bath in a subsequent phase of its lifetime.
EXAMPLES
[0197]
[0198] In each of the examples in
[0214] Throughout the process, the pH, temperature and agitation were maintained, and the plating reaction was observed by the bubbles evolving from the substrates. This process was performed on each of the plating baths in
[0215] These examples demonstrate the following combinations of multi-purpose plating baths, as accomplished by the present invention: [0216] High phosphorous to medium phosphorous [0217] High phosphorous to low phosphorous [0218] Low phosphorous to medium phosphorous [0219] Medium phosphorous to medium phosphorous with PTFE [0220] High phosphorous to medium phosphorous with boron nitride [0221] High phosphorous to medium phosphorous with diamond [0222] A single component system to a multiple component system [0223] A single component system to a single component system. [0224] A multiple component system to a single component system [0225] The use of auxiliary solutions [0226] Acid to alkaline [0227] Alkaline to acid [0228] Useless to useful [0229] Lower hardness to higher hardness [0230] Compressive stress to tensile stress [0231] Slower plating rate to higher plating rate [0232] Higher corrosion resistance to lower corrosion resistance
[0233] These examples include the use of the following plating solutions: [0234] One-Plate 2001Q-2.0 as sold by Surface Technology, Inc. of Ewing, NJ USA. [0235] One-Plate 1001Q as sold by Surface Technology, Inc. of Ewing, NJ USA. [0236] One-Plate 1001S as sold by Surface Technology, Inc. of Ewing, NJ USA. [0237] One-Plate 3001Q-2.0 as sold by Surface Technology, Inc. of Ewing, NJ USA. [0238] Ni-Plate 201 A, B, and C as sold by Surface Technology, Inc. of Ewing, NJ USA. [0239] Ni-Plate 100 A and C as sold by Surface Technology, Inc. of Ewing, NJ USA. [0240] Ni-Plate 300 A, B, and C as sold by Surface Technology, Inc. of Ewing, NJ USA. [0241] Ni-Plate 161 E and C as sold by Surface Technology, Inc. of Ewing, NJ USA. [0242] Ni-Slip 500 D-NPF as sold by Surface Technology, Inc. of Ewing, NJ USA. [0243] Ni-Slip 25 D as sold by Surface Technology, Inc. of Ewing, NJ USA. [0244] Composite Diamond Coating CDC D-2 as sold by Surface Technology, Inc. of Ewing, NJ USA.
[0245] Other combinations and utility can further be achieved according to the novel method of the present invention whereby a single plating bath is operated to provide for multiple purposes.
[0246] A sample technical data sheets associated with these solutions is attached as Appendix 1, incorporated herein by reference.
[0247] A sample safety data sheets associated with solutions is attached as Appendix 2, also incorporated herein by reference.
[0248] It was observed in Experiment 7, that the plated layer looked unique for an electroless nickel-boron nitride coating compared to the conventional appearance for such a coating in the plating industry. Rather than the traditional semi-bright or matte nickel finish, the plated layer in this example of the present invention had a matte gray/blue appearance similar to a typical electroless nickel-PTFE coating. Moreover, the electroless nickel-boron nitride coating of this example also had a physical appearance and tactile feel more consistent with a typical electroless nickel-PTFE coating. Upon microscopic examination of the electroless nickel-boron nitride coating of Experiment 7, the surface of the coating exhibited a surface profile with a texture similar to electroless nickel-PTFE consistent with what is often described as an orange peel surface. As there are certain deficiencies and concerns with the use of PTFE in general, and in plating applications specifically, an alternative to PTFE has long since been desirable. The use of boron nitride has been the most commercially preferred alternative to PTFE in the electroless nickel industry. While the use of boron nitride has some advantages over PTFE to the plater as well as the plated layer, the surface finish of the typical plated layer of electroless nickel with boron nitride is often not as useful to applications requiring low friction and release properties because such coatings lack the surface profile of electroless nickel-PTFE coatings. Therefore, the plating conditions including plating rate and other parameters of the present invention have benefits to producing electroless nickel-boron nitride coatings with improved properties.
[0249] Example 9 demonstrates the utility of the present invention to transform an acid type EN plating bath with a high number of MTOs, that was no longer useful for its initial purpose to produce a medium phosphorous EN coating, into an alkaline EN plating bath that was able to be used for a different purpose. This different purpose was to serve as a strike or flash plating bath for plating aluminum substrates as disclosed in the present invention. This is an additional example of how the present invention can avoid the make up of additional plating baths, reduce waste, increase utility to the plating operator, and other benefits. Example 10 similarly demonstrates such utility.