Stripping solution for zinc/nickel alloy plating from metal substrate

Abstract

The present disclosure relates generally to the field of electroplating and electroless plating. More specifically, the present disclosure relates to plating solutions and plating removal/stripping solutions for stripping zinc/nickel alloy plating from substrates.

Claims

1. A method for removing zinc/nickel alloy plating from a plated substrate comprising the steps of: immersing a plated substrate into a solution comprising a basic compound and an amine for a predetermined time, said plated substrate comprising a zinc/nickel alloy plating; and removing the zinc/nickel plating from the substrate.

2. The method of claim 1, before, after or concurrently with the step of removing the zinc/nickel plating from the substrate, further comprising the step of: removing debris attached to the substrate by wiping, applying ultrasound, applying agitation, or combinations thereof.

3. The method of claim 1, wherein the solution is maintained at a temperature of from about 60° F. to about 200° F.

4. The method of claim 1, wherein the basic compound comprises sodium hydroxide, potassium hydroxide and combinations thereof.

5. The method of claim 1, wherein the basic compound is maintained in the solution at a concentration of from about 10% to about 35% by weight.

6. The method of claim 1, wherein the amine comprises triethanolamine, N-aminoethylethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentathylenehexamine, and combinations thereof.

7. The method of claim 1, wherein the amine is maintained in the solution at a concentration of from about 1% to about 25% by weight.

8. The method of claim 1, wherein the solution is maintained at a pH of greater than about 11.

9. The method of claim 1, wherein the plated substrate comprises steel, stainless steel, aluminum, aluminum alloy, titanium, titanium alloy, copper, copper alloy, and combinations thereof.

10. A method for replenishing a zinc/nickel alloy plating solution comprising zinc ions and nickel ions, said method comprising the steps of: immersing a plated substrate into a solution comprising a basic compound and an amine for a predetermined time, said plated substrate comprising a zinc/nickel alloy plating; and removing zinc ions and nickel ions from the substrate.

11. The method of claim 10, wherein the solution is maintained at a temperature of from about 60° F. to about 200° F.

12. The method of claim 10, wherein the basic compound is maintained in the solution at a concentration of from about 10% to about 35% by weight.

13. The method of claim 10, wherein the amine is maintained in the solution at a concentration of from about 1% to about 25% by weight.

14. The method of claim 10, wherein the basic compound comprises sodium hydroxide, potassium hydroxide and combinations thereof.

15. The method of claim 10, wherein the amine comprises triethanolamine, N-aminoethylethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentathylenehexamine, and combinations thereof.

16. A plating solution for plating zinc/nickel-containing alloy onto a substrate, said plating solution comprising: an amount of basic compound in an amount of from about 10% to about 35% by weight; wherein an amount of zinc and nickel ions are replenished to the plating solution by immersing a substrate plated with a zinc/nickel alloy, stripping zinc ions and nickel ions from the substrate, and returning the zinc ions and nickel ions to the plating solution.

17. The plating solution of claim 16 further comprising: an amount of amine in an amount of from about 1% to about 25% by weight, wherein the amine comprises triethanolamine, N-aminoethylethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentathylenehexamine, and combinations thereof.

18. The plating solution of claim 16, wherein the basic compound comprises sodium hydroxide, potassium hydroxide and combinations thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Having thus described variations of the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

(2) FIG. 1 is a flow chart showing an aspect of the present disclosure; and

(3) FIG. 2 is drawing of an aircraft comprising parts plated using reclaimed zinc and nickel according to aspects of the present disclosure.

DETAILED DESCRIPTION

(4) Known stripping solutions that remove Zn/Ni alloy plating from substrates often comprise ammonium nitrate that generate hydrogen that can undesirably embrittle the substrate, resulting in the need to remediate the substrate by further processing the stripped substrate (e.g. baking processes) before the substrate can be re-used.

(5) According to an aspect of the present disclosure, a basic compound-containing stripping solution that is highly basic, along with the addition of an amine, has now been shown to efficiently, reliably and cost-effectively strip zinc/nickel plating from metal substrates, without imparting any embrittlement to the metal substrate. According to one aspect, the basic compound comprises a compound such as, for example, sodium hydroxide, potassium hydroxide and combinations thereof in an amount of from about 10 to about 35% by weight. In a further aspect, the amine comprises, for example, triethanolamine (TEA), N-aminoethylethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentathylenehexamine, and combinations thereof in an amount of from about 1 to about 25% by weight. According to one embodiment, sodium hydroxide is provided to a solution along with TEA. By using a non-acidic stripping solution (and thus preventing the generation of hydrogen to the stripping solution system), hydrogen embrittlement and other attack of a metal substrate, such as, for example, steel, is significantly minimized, and/or substantially eliminated. While a solution having a basicity (basic pH) of greater than at least about 11 (and in one aspect a solution with a pH from about 11 to about 14) has now been shown to work as a zinc/nickel stripping solution, it now also has been demonstrated that, as the solution basicity increases, and an amine such as, for example, N-aminoethylethanolamine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentathylenehexamine, and combinations thereof, is introduced to the stripping solution, the stripping time decreases significantly (and the stripping rate increases significantly). Without being bound by any particular theory, it is believed to be advantageous to maintain the pH as high as possible, (e.g., greater than about 11), without thickening the solution to the point of an unusable viscosity.

(6) FIG. 1 is a flow chart showing one aspect of the present disclosure. According to process 10, a substrate that has been plated with a Zn/Ni alloy plating 12 is subjected to a step of immersing the substrate 12 into a solution comprising a basic compound and an amine maintained at a pH of from about 11 to about 14, 14. Optionally, the solution comprising a basic compound and an amine 14 may be subjected to a one of two heating steps; 1) the solution comprising a basic compound and an amine is heated to a temperature above room temperature before the substrate is immersed in the solution 16a; or 2) the solution comprising a basic compound and an amine is heated to a temperature above room temperature after the substrate is immersed in the solution 16b. Room temperature is understood to be an ambient temperature of from about 65° F. to about 85° F. The substrate is then left immersed in the solution comprising a basic compound and an amine for a predetermined amount of time (not shown) and Zn/Ni alloy plating is removed from the substrate surface 17. It is understood by those skilled in the field that the stripping time will depend upon the thickness of the Zi/Ni alloy plating being stripped. Concurrently with, or subsequent to, the removal of the Zn/Ni alloy plating being stripped from the substrate, “smut” or other debris is often formed on the substrate surface. As a result, the stripped substrate is then subjected to a step to remove debris from the substrate surface 18.

EXAMPLES

(7) Experiments were conducted to determine the effectiveness of a stripping solution comprising sodium hydroxide/triethanolamine to remove zinc/nickel alloy plating from steel substrate test specimens plated with a zinc/nickel alloy. Test specimen steel substrates were 4130 steel cut into 1″×4″ rectangles, having a thickness of about 0.04″. The test specimens were plated with approximately 1 mil (0.001″) zinc/nickel alloy. The test specimens were then immersed in various stripping solutions. The selected stripping solution and the results obtained are shown below in Table 1. Room temperature is understood to be a temperature of from about 65 to 85° F.

(8) TABLE-US-00001 TABLE 1 Agitation Solution Stripping Time Y/N Temperature ° F. Ammonium Approx. 24 hours N Room Temp. Nitrate/H.sub.2O 150 g/l Ammonium 4-5 hours N Room Temp. Nitrate/H.sub.2O 240 g/l Ammonium 20 min. Y Room Temp. (pH Nitrate/H.sub.2O adjusted to 8.0 312 g/l with Ammonium Hydroxide Turco Alkaline Rust 30 min. N 160 Remover - MAC 240 g/l Turco Alkaline Rust 70 min. N Room Temp. Remover - MAC 240 g/l Sodium Hydroxide 70 min. N Room Temp. 240 g/l Sodium Hydroxide 30 min. N Room Temp. 20% by weight Sodium 15 min. N Room Temp. Hydroxide/TEA 20%/15% by weight Zn/Ni Plating 12 hours N Room Temp. solution (Dipsol) [Dipsol of America, Livonia, Mich.]

(9) The systems and methods set forth herein are contemplated for use with producing zinc/nickel alloy plated components for use in manned or unmanned vehicles or objects of any type or in any field of operation, such as in a terrestrial and/or non-terrestrial and/or marine or submarine setting. A non-exhaustive list of contemplated objects include, manned and unmanned aircraft, spacecraft, satellites, terrestrial, non-terrestrial vehicles, and surface and sub-surface water-borne vehicles, etc., as well as stationary objects. FIG. 2 shows an aircraft 20 comprising a fuselage panel 24 from a fuselage section 22. Fuselage section 22 comprises component parts (not shown) that may themselves comprise a substrate material plated with a Zn/Ni alloy plating solution that has been at least partially replenished with zinc and nickel that has been recovered and introduced into the plating tank/bath by immersing a substrate plated with Zn/Ni alloy and then stripping the Zn/Ni alloy plating from the substrate.

(10) When introducing elements of the present disclosure or exemplary aspects or embodiment(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. While the preferred variations and alternatives of the present disclosure have been illustrated and described, it will be appreciated that various changes and substitutions can be made therein without departing from the spirit and scope of the disclosure. Although specific aspects have been described, the details of these aspects are not to be construed as limitations.