Porous, flow-through consumable anodes for use in selective electroplating

Abstract

A method for electrodepositing a coating/free-standing layer on a workpiece in an electrolytic cell includes moving the workpiece and an anode applicator tool having a consumable anode insert relative to each other; anodically dissolving a metal from the insert and cathodically depositing the metal on the workpiece; providing flow of electrolyte solution through the insert to ensure that greater than 90% of the anodic reaction is represented by dissolution of the metal; recirculating collected electrolyte solution exiting the electrolytic cell through the insert; applying an electric current to the electrolytic cell; maintaining a concentration of the anodically dissolved metal within 25% of each Ampere-hour per liter of electroplating solution; and creating a cathodic electrodeposit on the workpiece which includes the anodically dissolved metal, the chemical composition of the deposit varying by less than 25% in the deposition direction over a selected thickness of up to 25 microns of the deposit.

Claims

1. A method for selectively electrodepositing a coating or a free-standing layer on a workpiece in an electrolytic cell comprising: moving the workpiece to be coated and an anode applicator tool relative to each other during the electrodeposition process, the anode applicator tool including a consumable active anode insert; providing a permanent substrate which is electrochemically inert and pervious to the electrodeposition electrolyte and providing a sacrificial anode metallic material coating/layer having a thickness between 1 micron and 5 cm, the permanent substrate together with the sacrificial anode metallic material coating/layer defining the consumable active anode insert; anodically dissolving a metallic material from the consumable anode insert and cathodically depositing the metallic material on the workpiece; providing sufficient flow of electrolyte solution through the consumable anode insert to ensure that greater than 90% of the anodic reaction is represented by dissolution of the metallic material; collecting the electrolyte solution exiting the electrolytic cell and recirculating the collected electrolyte solution through the consumable anode insert; applying an electric current having a duty cycle between 5% and 100% to the electrolytic cell; maintaining a concentration of the metallic material being anodically dissolved from the consumable anode insert in the electrolyte solution within 25% of each Ampere-hour (Ah) per liter of electroplating solution; and creating a cathodic electrodeposit on the workpiece which includes the metallic material anodically dissolved from the consumable anode insert, the chemical composition of the deposit varying by less than 25% in the deposition direction over a selected thickness of up to 25 microns of the deposit, the selected thickness being a portion of the overall deposit thickness in deposition direction.

2. The method of claim 1, further including providing electrolyte flow through the consumable anode insert to ensure that the internal-resistance-free cell voltage is less than 1.2V.

3. The method of claim 1, further including configuring the applicator tool so that the ratio between a surface area of the consumable active anode insert wetted by the electrolyte solution and an interfacial area is greater than or equal to 2.

4. The method of claim 3, further including configuring the applicator tool so that the surface area of the consumable active anode insert wetted by the electrolyte solution is at least 100% greater than the interfacial area.

5. The method of claim 1, further including providing the consumable active anode insert with a porosity greater than or equal to 5%.

6. The method of claim 5, further including providing the consumable active anode insert with a porosity greater than or equal to 25%.

7. The method of claim 1, further including providing the consumable active anode insert devoid of carbon and/or graphite near an interfacial area.

8. The method of claim 1, further including providing the consumable active anode insert with an electrolyte flow rate through the consumable active anode insert of at least 1 ml/min per Ampere applied average anodic current or peak anodic current.

9. The method of claim 1, wherein by modulating the electric current, each of the metallic material layers created on the workpiece has one of a fine-grained microstructure and/or an amorphous microstructure.

10. The method of claim 1, further including providing the consumable active anode insert with a first anode comprising a first metallic material and a second anode comprising a second metallic material, electrically isolating the first metallic material from the second metallic material, and selectively depositing the first metallic material and the second metallic material on the workpiece by applying a first electric current to the first anode and applying a second electric current to the second anode.

11. The method of claim 1, further including positioning an electrically non-conductive, electrodeposition electrolyte pervious absorber between and in intimate contact with both the consumable anode insert and the workpiece.

12. The method of claim 11, further including configuring the applicator tool to be at least partially conductive, and positioning an insulating frame member between the applicator tool and the absorber to prevent the applicator tool from participating in the electrodeposition of the metallic material on the workpiece surface.

13. The method of claim 12, further including configuring the insulating frame member to include a cavity for housing the consumable anode insert, an opening of the cavity defining an electrolytic interfacial area, providing each of the consumable anode insert and the absorber with an electrolyte flow rate therethrough of one of at least 1 ml/min per applied Ampere average anodic current or peak anodic current and at least 1 ml/(mincm.sup.2) interfacial area.

14. The method of claim 1, wherein the metallic material from the consumable anode insert has a fine-grained microstructure and/or an amorphous microstructure.

15. A method for selectively electrodepositing a coating or a free-standing layer on a workpiece in an electrolytic cell comprising: moving the workpiece to be coated and an anode applicator tool relative to each other during the electrodeposition process, the anode applicator tool including a porous consumable active anode insert comprising a metallic material and having a porosity of at least 5%; providing a permanent substrate which is electrochemically inert and pervious to the electrodeposition electrolyte and providing a sacrificial anode metallic material coating/layer having a thickness between 1 micron and 5 cm, the permanent substrate together with the sacrificial anode metallic material coating/layer defining the consumable active anode insert; and providing sufficient flow of electrolyte solution through the porous consumable anode insert to ensure that greater than 90% of the anodic reaction is represented by dissolution of the metallic material from the porous consumable anode insert.

16. The method of claim 15, further including positioning an electrically non-conductive, electrodeposition electrolyte pervious absorber between and in intimate contact with both the consumable anode insert and the workpiece.

17. The method of claim 16, further including configuring the applicator tool to be at least partially conductive, and positioning an insulating frame member between the applicator tool and the absorber to prevent the applicator tool from participating in the electrodeposition of the metallic material on the workpiece surface.

18. The method of claim 15, further including providing the consumable active anode insert with an electrolyte flow rate through the consumable active anode insert of at least 1 ml/min per Ampere applied average anodic current or peak anodic current.

19. A method for selectively electrodepositing a coating or a free-standing layer on a workpiece in an electrolytic cell comprising: moving the workpiece to be coated and an anode applicator tool relative to each other during the electrodeposition process, the anode applicator tool including a porous consumable active anode insert comprising a metallic material and having a porosity of at least 5%; providing a permanent substrate which is electrochemically inert and pervious to the electrodeposition electrolyte and providing a sacrificial anode metallic material coating/layer having a thickness between 1 micron and 5 cm, the permanent substrate together with the sacrificial anode metallic material coating/layer defining the consumable active anode insert; and providing sufficient flow of an electrolyte solution containing at least one ion selected from the group consisting of chloride-ion, phosphorous-ion and hypophosphorous-ion through the porous consumable anode insert to ensure that greater than 90% of the anodic reaction is represented by dissolution of the metallic material from the porous consumable anode insert.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In order to better illustrate the present disclosure by way of examples, descriptions are provided for suitable embodiments of the method/process/apparatus according to the present disclosure in which:

(2) FIG. 1 illustrates an exemplary embodiment of the anode applicator tool.

(3) FIG. 2 illustrates an alternative exemplary embodiment of the anode applicator tool.

(4) FIG. 3 illustrates polarization curves (cell voltages and IRF-cell voltages) for the cathodic electrodeposition of CoP alloys using DSAs and CoSAs.

(5) FIG. 4 illustrates cell voltages versus time for the cathodic electrodeposition of CoP alloys using three different anodes.

(6) FIG. 5 illustrates IR-corrected polarization curves for the cathodic electrodeposition of NiP alloys using DSAs and NiSAs at 30 C., 60 C. and 70 C.

(7) FIG. 6 illustrates polarization curves (cell voltages and IRF-cell voltages) for the cathodic electrodeposition of pure Fe using DSAs and FeSAs at room temperature.

(8) FIG. 7 illustrates the Fe.sup.3+ concentration in the electrolyte with increased plating time expressed in Ah/l for the cathodic electrodeposition of n-NiFe using a DSA between 0 and about 1.75 Ah/l followed by using dual SAs (Ni-SA and Fe-SA) until 3.25 Ah/l at 55 C.

DETAILED DESCRIPTION

(9) The present disclosure relates to selective plating/brush plating applicators employing dimensionally stable flow-through soluble/consumable-anodes (DSSA) for use in electroplating at high deposition rates. The novel consumable anode inserts employed are perforated/porous, do not disintegrate with increased active material consumption, and comprise a surface area greater than the geometric interfacial anode/cathode. During electroplating, electrolyte is pumped through the soluble anode inserts at a sufficient flow rate to enable the anodic dissolution of the consumable anode active material minimizing or avoiding the generation of oxygen, chlorine gas and/or the anodic oxidation of P-bearing ions in the electrolyte.

(10) Selective and brush plating methods are used, e.g., to repair damaged components in-situ by electroplating on a limited area instead of immersing entire components into plating bath, which results in remarkable savings of cost and man-power. With the recent commercial introduction of various nanocrystalline materials in the form of homogenous coatings, graded coatings or multi-layer laminate coatings by Integran Technologies Inc., of Toronto, Canada, the assignee of the present application, selective plating processes are required for, among other, field repair purpose of fine-grained materials.

(11) As highlighted above when employing non cumsumbale, dimensionaly stable anodes (DSAs), the anode reactions do not liberate metal ions required in the cathodic depostion. Therefore, metal ions for the cathodic reduction must be supplied solely from the electrolyte solution. As metal ions in the electrolyte are consumed during the electrodeposition process, the metal-ions in the electrolyte are depleted and must be replenished. In the case of using DSAs in aqueous electrolytes, the desired anodic reaction is typically oxygen evolution. Depending on the anode material, the electrolyte composition and operating parameters, include, but not limited to, temperature and current density; however, other anodic reactions can take place such as chlorine evolution (from chloride bearing electrolyes) and direct or indirect oxidation of P.sup.3+-ions or P.sup.+-ions to phosphate (P.sup.5+-ions, or the undesired oxidation of metal ions to higher valencies. This makes bath maintenance more complicated unless the depleted electrolyte is discarded, which is costly and generates added hazardous waste. Moreover, using DSAs undesirable chemical species, including but not limited to chlorine gas, may be liberated as a result of the anodic reactions which may represent a health and safety hazard for the operator. The anodic gas release in a compact electrolytic cell design such as employed in brush plating applications is highly undesired.

(12) Efforts to develop commercially viable selective and/or brush plating technologies involving the use of DSA, e.g., for P-containing Co deposits, result in a rapid deterioration of the plating solution and the coating quality. Specifically, using conventional brush plating tools with DSAs with chloride and sulfate based electrolytes for depositing CoP based coatings, the following problems were noted: a. Rapid decrease of the Co.sup.2+ concentration and the pH in electrolyte, necessitating frequent addition of CoCO.sub.3; b. Significant Cl.sub.2 evolution; c. Rapid drop in deposit P level in the coating with increasing Ah/l electrolyte use requiring frequent (more often than every 10 min) or continuous additions of H.sub.3PO.sub.3; d. Additions of H.sub.3PO.sub.2 in addition to H.sub.3PO.sub.3 (as H.sub.3PO.sub.3 additions alone are not always sufficient to maintain desired P-deposit levels in the coating) to maintain a uniform deposit composition; e. Increase in solution density which ultimately requires a premature disposal of the solution (approx. between 75 and 150 Ah/l) as the solution becomes too viscous to pump.

(13) Without trying to be bound by the theory, it is believed the main reason for the poor consistency, stability and longevity of brush plating solutions frequently is due to the use of conventional DSAs.

(14) Typical Watts Ni or Co based electrolytes contain chloride ions and, due to the high overpotential for oxygen evolution (/>0.5V), the anodic reaction is not limited to oxygen generation and, depending on the nature of the DSA and the electrolyte, usually chlorine gas is evolved.

(15) Specific to P containing deposits (NiP, CoP, FeP), it is believed chlorine produced on the DSA oxidizes phosphorous ions in the electrolyte or, possibly, phosphorous ions could be oxidized anodically directly, resulting in depletion of phosphorous ions by conversion to phosphoric ions. The result is a rapid local depletion of P.sup.+/P.sup.3+-ions in the brush electrolyte solution causing a commensurate reduction of the P content in the coating and solution longevity and stability issues.

(16) The inventors have surprisingly discovered that dimensionally stable, consumable anodes (DSSAs) provide a viable approach for brush plating when using electrolytes containing chlorides and/or H.sub.3PO.sub.2 and H.sub.3PO.sub.3 and/or metal ions which can be anodically oxidized. Without considering overpotentials for specific anodic reactions, it is apparent that in the case of plating Ni or Co from chloride containing electrolytes a change in the anodic reaction from O.sub.2/Cl.sub.2 evolution to Co or Ni dissolution lowers the anodic potential and reduces the cell voltage by >1.5V.

(17) Benefits of employing consumable anodes for use in brush plating include (i) lower operating cell voltages and reduced power consumption, (ii) increased worker health/safety by avoiding toxic gas evolution, (iii) simpler bath management enabling electrolytes to be used much longer, i.e., increased Ah/l use, (iv) reducing the overall complexity and cost of field repair and, (v) enabling a consistent and uniform cathodic deposit.

(18) The inventive concept is based on converting/retrofitting DSA brush anode applicators to dimensionally stable, high surface area soluble/consumable anodes (DSSAs) by suitably designing brush applicator tools. The conversion entails employing consumable anode inserts with pores and/or voids which provide for: (i) a high active interface surface area anode (active anode surface area/anode cathode interface area 1, preferably 2) while (ii) providing for relatively unimpeded and sufficiently high electrolyte flow; (iii) maintaining the physical shape and/or integrity of the consumable anode insert despite the anodic dissolution of metal ions; (iv) achieving uniform anodic dissolution; and (v) avoiding significant anode size changes and clogging of the absorber by powders or dislodged active anode fragments. A further benefit is to be able to replace and/or replenish consumable anode inserts conveniently to restore or replenish the anode capacity without having to dispose of the anode applicator.

(19) These objectives can be accomplished by creating, e.g., an anode cavity in a brush plating applicator as illustrated in FIG. 1 filled with suitable anode rounds (pellets, flakes, etc.) that can be held together by a suitable binder or electrolyte pervious anode inserts such as open cell foams or perforated plates that have been plated with the desired metal or alloy, e.g., Ni, Co, Fe and Cu.

(20) Suitable consumable anode inserts comprising, e.g., Ni, Co, Fe or Cu of desired size and shape can be conveniently prepared by any well-known metal deposition process. Grain-refined and/or amorphous consumable anode active material layers are particularly desirable as fine-grained and amorphous layers typically anodically dissolve more uniform than coarse-grained materials. Open cell foam or other solid porous bodies enabling unrestricted electrolyte flow throughout can be pre-plated with the desired metals and or replenished in a conventional tank plating set up.

(21) Electroplating/Electroforming Description:

(22) A person skilled in the art of plating will know how to generally electrodeposit selected coarse-grained, fine-grained and/or amorphous metals, alloys or metal matrix composites choosing suitable plating bath formulations and plating conditions as described in US 2005/0205425 and US 2010/0304172, both assigned to the same assignee as the present application.

(23) The prior art describes that dimensionally stable anodes (DSA) or consumable anodes (SA) can be used interchangeably in electrodeposition. Suitable DSAs include platinized metal anodes, platinum clad niobium anodes, graphite or lead anodes or the like. Consumable anodes include metal or alloy rounds, chips and the like, e.g., placed in a suitable anode basket made out of, e.g., Ti, and preferably covered by suitable anode bags.

(24) As highlighted in the objectives, when using dimensionally-stable, consumable anodes, metal-ions lost from the electrolyte through reduction to the coating on the cathode get constantly replenished by anodically dissolving the same metal or alloy. Further benefits of using dimensionally-stable, consumable anodes include a substantial reduction in the cell voltage due to the potential difference between metal-oxidation and oxygen evolution and much simpler bath maintenance. Consumable anodes employed in a confined space using moving electrodes need to be insensitive to the position of space, i.e., consumable anodes can be operated in all three-dimensions of space including upside down.

(25) When using consumable anodes in tank plating set-ups, metal-ion depletion in the electrolyte is prevented by using metal rounds as consumable stationary anodes, alternatively metal-ion depletion is prevented by suitable bath additions. The addition of rounds or other loose anode fragments is desired, as this is (i) a convenient way of adding/topping up the active anode, (ii) the anode settles with increased use through gravity so the anode level can easily be monitored and (iii) electrical contact between the individual pieces is maintained by the anodes own weight and gravity as the anode is stationary, i.e., it doesn't change its position during the plating operation.

(26) In the case of brush plating, however, the anode is not stationary and it needs to follow the contours of, at times, complex workpieces. Brush plating applicators need to be operated horizontally, vertically as well as upside down, i.e., they need to be insensitive to orientation. Therefore consumable anode cages employing anode rounds which settle due to gravity as they are being used in tank plating are not suitable. Low surface area anode plates can passivate and, while being amenable to selective plating, cannot be easily used in typical brush plating set ups which requires the electrolyte to be circulated through the brush applicator. Brush applicators furthermore need to be compact and robust as in a number of applications, including, but not limited to field repair; they are simply moved back and forth over the workpiece by hand by an operator.

(27) The anode brush system, which is typically portable, comprises the anode brush applicator, suitable piping to provide electrolyte from a reservoir that contains a heating system and a filter, and an electrolyte collection system which gathers the electrolyte exiting the anode applicator after contacting the workpiece. After the system is set up, rendered operational and suitably contacts the appropriately activated workpiece(s), direct or pulsed current (including the use of one or more cathodic pulses, and optionally anodic pulses and/or off times) is applied between the cathode(s) and the anode(s). A suitable duty cycle is in the range of 10% to 100%, preferably between 50 and 100% and suitable applied average cathodic current densities are in the range of 25 to 2,500 mA/cm.sup.2, preferably between about 100 and 1,000 mA/cm.sup.2. As the person skilled in the art knows, the microstructure (crystalline or amorphous deposits) of the cathodic coating can furthermore be affected by a number of variables including, but not limited to, the bath chemistry, the electrical wave forms, cathode surface flow conditions and bath temperature. As desired, homogenous, layered and/or graded cathodic deposits can be prepared using the DSSAs described herein.

(28) As indicated above active anode brush applicator inserts according to the present invention are sufficiently permeable to the electrolyte and contain significant void space to enable a relatively unimpeded electrolyte flow through the electrochemically active anode structure. The porosity of the anode inserts should be maintained above 10%, preferably above 25%.

(29) As indicated, powder, flakes, junks and the like, i.e., loose aggregates of the consumable anode material(s) can, in principal, be used for the electrochemically active anode structure/anode inserts. The disadvantage of this approach relates to electrical contact issues as the volume/weight of the consumable anode declines with increased use, accompanied with a change in the electrolyte permeability and the concerns associated with releasing fine powder into the electrolyte solution and/or the puncture of the absorber leading to short circuits. Suitable binders can be employed to convert loose aggregates into a rigid structure, as highlighted. Alternatively, the loose aggregate containing soluble anode inserts are not utilized to exhaustion, e.g., not more than 75.sup.wt%, preferably not more than 50.sup.wt% and even more preferably not more than up to 25.sup.wt% of the anode material is consumed in the anodic reaction before the soluble anode insert is replaced, replenished, and/or the fines are removed and the anode insert is repacked to account for the mass and volume loss and ensure good electrical contact.

(30) According to one embodiment of the present disclosure, the active consumable anode material(s) is/are deposited on a permanent substrate which does not act as an electrochemically active anode structure at the plating conditions used. In this case, while the weight of the anode drops with increased usage, the overall volume and electrolyte permeability remains relatively unchanged as the electrochemically active consumable anode layer dissolves eventually exposing the underlying permanent substrate. This approach assures fairly uniform plating conditions until substantially all electrochemically active anode structure(s) is/are consumed assuring a uniform cathodic deposit throughout the consumable anode insert life.

(31) According to one embodiment of the present disclosure, the permanent anode substrate can be electrically conductive which is desired as the Ohmic drop with increased anode usage is minimized. However, depending on the nature of the electroplating bath and plating conditions it may be challenging to find an electrically conductive permanent, however, electrochemically inactive material. As highlighted, chloride containing electrolytes, C-containing substrates (carbon, graphite, carbon nanotubes, graphene) are therefore undesired. Electrochemically inert metals/alloys are preferred for use as permanent substrates. Alternatively, electrically conductive, yet electrochemically inert substrates can also include oxides such as, e.g., Ti-suboxides of the Magnli phases (Ti.sub.nO.sub.2n-1, n=5-6). In yet another embodiment, polymeric substrates are chosen, which could optionally be rendered electrically conductive through the employ of conductive filler materials.

(32) FIG. 1 shows a cross sectional view of one embodiment of a brush plating apparatus according to the present disclosure. A workpiece 10 (i.e., cathode) to be plated is connected to the negative outlet of a power source 12. An anode brush applicator 14 includes a handle 16 and an at least partially conductive anode brush housing 18 connected to the handle. The conductive anode brush housing 18 houses a consumable anode insert 20 in an anode cavity 22. The consumable anode insert 20 preferably includes a permanent, electrochemically inert, electrolyte pervious substrate and a sacrificial anode metallic coating/layer provided on the permanent substrate and having a thickness between 1 m and 5 cm. The sacrificial anode metallic coating/layer is an active consumable anode material capable of being anodically dissolved when current is supplied to the apparatus. The consumable anode insert 20 defines an anode surface area, and reference numeral 24 depicts an electrode interface area between the anode (i.e. the anode brush applicator 14) and cathode (i.e., the workpiece 10). Alternatively, electrical connections can be provided to connect the power supply to the consumable anode insert. If required, an insulating frame member 30 prevents the conductive anode brush housing 18 from participating in the plating reaction and its frame opening defines the electrolytic interface area 24. An absorbent separator (wick) 32 provides for the electrolyte space between the anode and cathode and enables the continuous electrolyte flow from the consumable anode insert to the workpiece 10. The anode brush housing contains channels 34 for supplying electrolyte solution 36 from (preferably) a temperature controlled tank (not shown) to the consumable anode insert 20. The electrolyte solution dripping from the absorbent separator 32 is optionally collected in a tray 40 and recirculated to the tank. The absorbent separator 32 containing the electrolyte solution 36 also electrically insulates the anode brush housing 18 and the consumable anode insert 20 from the work-piece 10 and adjusts the spacing between the anode (i.e. the anode brush applicator 14) and cathode (i.e., the workpiece 10). The anode brush handle 16 can be moved over the workpiece 10 either manually or using a motorized motion.

(33) FIG. 2 schematically shows a frontal view of a brush plating tool 50 comprising another exemplary consumable anode insert 52 according to the present disclosure. The consumable anode insert 52 is designed for use with two consumable anodes. Specifically, the consumable anode insert 52 includes two consumable anodes 54 and 56 provided in a recessed non-conductive housing 60. The electrolyte pervious, consumable anode 54 containing a consumable metal M.sub.1 deposited on a suitable substrate S.sub.1 is connected to a power supply (not shown) via electrical contact 62. The electrolyte pervious, consumable anode 56 containing a consumable metal M.sub.2 deposited on a suitable substrate S.sub.2 is connected to another power supply (not shown) via electrical contact 64. The electrolyte pervious, consumable anodes 54 and 56 have a generally comb type design/configuration relative to each, cover a significant portion of the total anode area, and are physically separated by a spacer, separator, or equivalent depicted at reference numeral 66. The electrolyte pervious, consumable anodes 54 and 56 are electrically isolated from each other to enable to direct the desired anodic current A.sub.1 and A.sub.2, to the consumable anodes 54 and 56 from their respective power supplies. The negative lead of both power supplies is connected to the workpiece and the individual anodic currents are regulated to achieve the desired dissolution rates of metal M.sub.1 and M.sub.2. The brush plating tool 50 is wrapped in a suitable absorber and enables the continuous electrolyte flow from the consumable anode insert 52 to a workpiece (not shown).

(34) The electrolyte used can be temperature controlled and passed through the anode applicator tool to maintain the desired temperature range. The absorbent separator material contains and distributes the electrolyte solution between the anode and the workpiece (cathode), prevents shorts between anode and cathode and brushes against the surface of the area being plated. It is believed that the mechanical rubbing or brushing motion imparted to the workpiece during the plating process influences the quality and the surface finish of the coating and enables fast plating rates. Selective plating electrolytes are formulated to produce acceptable coatings in a wide temperature range from as low as 20 C. to 95 C. As the workpiece is frequently large in comparison to the area being coated, selective plating is often applied to the workpiece at ambient temperatures, ranging from as low as 20 C. to as high as 45 C. Unlike typical electroplating operations, in the case of selective plating the temperature of the anode, cathode and electrolyte can vary substantially. Salting out of electrolyte constituents can occur at low temperatures and the electrolyte may have to be periodically or continuously reheated to dissolve all precipitated chemicals.

(35) The following working examples illustrate the benefits of the present disclosure, specifically polarization curves obtained with brush plating CoP deposits using DSA and SA (Working Example 1); CoP deposits prepared using DSA and several SA under various conditions (Working Examples 2, 3 and 4), polarization curves obtained with brush plating NiP deposits using DSSA and SA (Working Example 5); polarization curves obtained with brush plating Fe deposits using DSSA and SA (Working Example 6); nanocrystalline Fe deposits prepared using DSSA and SA (Working Example 7); and nanocrystalline NiFe deposits prepared using DSSA and SAs (Working Example 8).

EXAMPLE 1

Co Plating, Polarization Curves DSA, DSSA

(36) A brush plating applicator was built and operated as illustrated in FIG. 1. Specifically, a brush plating applicator (model 3030-30A.sub.max) from Sifco Industries Inc. (Cleveland, Ohio, USA) was suitably modified as described above. More specifically, the graphite anode applicator was modified to enable the use of DSSA or SA inserts. The brush plating applicator contained an active anode cavity having an interfacial area of up to 21 cm.sup.2 and a depth of 5 mm machined into a graphite anode tool housing which provided for electrolyte feed channels and electrical contact and served as current collector for the active anode insert. A cotton absorber was placed over the brush applicator containing the anode insert. The absorber also served as electrolyte spacer and provided a gap between the anode and cathode of 1 mm.

(37) A plating solution was pumped into the modified anode brush applicator and exited through the anode inserts and the absorber onto a workpiece to be plated. The electrolyte dripping from the workpiece was collected in the temperature-controlled tank and re-circulated to the modified anode brush applicator and the anode inserts via a peristaltic pump. The temperature in the tank was adjusted as required, and the temperature measurements reported were taken on the electrolyte flowing/dripping from the workpiece. The total electrolyte solution for all trials was 1.7 liters and the electrolyte was circulated at a flow rate of 300 ml/min.

(38) The modified anode brush plating applicator was attached to and operated by a mechanical arm available from Sifco Industries Inc. (Cleveland, Ohio, USA) at 50 strokes per minute as set forth in US 2005/0205425, which is assigned to the same assignee as the present application. The rotation speed was adjusted to increase or decrease the relative anode/cathode stroke-speed. Electrical contacts were made on the brush handle (anode) and directly on the workpiece (cathode).

(39) The workpiece was a mild steel plate and a commercial chloride-based electrolyte for depositing fine-grained CoP alloys (available from Integran Technologies Inc., Toronto, Ontario, Canada, the assignee of the present application) containing H.sub.3PO.sub.3 as the P source was used. The workpiece was a 1020 cm mild steel plate that was suitably activated before the plating commenced.

(40) In this working example, DSA and Co-based consumable anode inserts (DSSA) with 5 cm.sup.2 interfacial area were employed and polarization curves measured using the Internal Resistance Free Measuring System IRF-PS155AL available from Rosecreek Technologies Inc. (Mississauga, Canada), which applies the well-known current interruption techniques described in U.S. Pat. No. 2,662,211. This measuring technique eliminates the resistive component of electrochemical cells and their components and enables the measurement of the electrochemical cell voltages and potential(s). The IRF measurement technique uses brief current interruption to eliminate Ohmic losses from the circuit. The time constant for the electrical resistance, capacitance and inductance of the conductors, electrodes, and electrolyte is typically in the range of microseconds whereas transients relating to the electrochemical polarization (concentration polarization, transport phenomena, etc.) are much slower, with time constants typically in the range of at least 100 millisecond.

(41) Polarization curves were obtained at temperatures between 20 C. and 80 C. in 20 C. intervals with an open-cell graphite-DSA and a dimensionally stable, consumable Co anode insert (Co coating on a polyurethane open cell foam) at current densities between 0 and 1,000 mA/cm.sup.2. The hardness of consumable Co anode layers was 38733 VHN (average grain size: 70 nm) as compared to Inco electrolytic Co rounds employed in tank plating which have a hardness of 230VHN (average grain size 5 microns). Table 1.1 highlights the applied cell voltages at four temperatures and three current densities for dimensionally stable and consumable anode inserts. The significantly reduction in applied cell voltage when employing fine-grained Co-consumable anodes is evident. Table 1.1 also expresses the flow rates in terms of ml/min normalized for anode-cathode geometrical interface area; ml/min normalized for applied average current; and ml/min normalized for the applied current density (in mA/cm.sup.2).

(42) TABLE-US-00003 TABLE 1.1 Current Density [mA/cm.sup.2] 100 500 1,000 20 C. DSA Voltage [V] 3.0 6.0 10.0 DSSA Voltage [V] 1.6 4.7 8.1 40 C. DSA Voltage [V] 2.6 5.7 8.2 DSSA Voltage [V] 1.3 3.5 5.7 60 C. DSA Voltage [V] 2.3 4.0 6.1 DSSA Voltage [V] 1.1 2.9 4.6 80 C. DSA Voltage [V] 2.3 4.2 6.2 DSSA Voltage [V] 1.1 2.8 4.5 Flow Rates [ml/(min .Math. cm.sup.2-Interface area)] 60.0 60.0 60.0 [ml/(min .Math. A.sub.av) 600.0 120.0 60.0 [(ml .Math. cm.sup.2)/(min .Math. A.sub.av)] 3,000.0 600.0 300.0

(43) FIG. 3 shows the polarization curves obtained at 20 C. for the DSA and consumable anodes (DSSA) between 0 and 1,000 mA/cm.sup.2. Applied cell voltages as well as IR-free cell voltages are displayed. Again, the significant reduction in applied cell voltage when employing Co-consumable anodes is evident.

EXAMPLE 2

Co Plating, Voltage with Increased Plating Time DSA, DSSA

(44) For Example 2, the plating set up and conditions described Example 1 were used. The workpiece was a mild steel plate. The electrolyte was preheated to 80 C. The total electrolyte solution for all trials was 1.7 liters and the electrolyte was circulated at a flow rate of 300 ml/min. The anode inserts had an effective interfacial area of 21 cm.sup.2 and the current density applied was 150 mA/cm.sup.2. DSA and Co-based consumable anodes (DSSA) were employed while electrodepositing CoP as in Example 1 for 90 minutes. FIG. 4 shows the graph for the DSA and two DSSAs (one using Co on a graphite foam substrate and the other one using Co on a polymer foam substrate). FIG. 4 indicates that the applied cell voltage for DSAs was between 5 and 6V, whereas the applied cell voltage for Co-DSSA inserts on a polymer substrate was 1.5V. Co-DSSA inserts using Co deposited on graphite foam initially had a low applied cell voltage which, after about 45 minutes of plating, increased from 2.5V to 4.5V indicating that anodic Co dissolution could not be maintained as the only anodic reaction. Evolution of chlorine gas became evident and it is believed that it coincided with the dissolution of the Co close to the absorber interface and, as soon as the graphite foam became exposed, chlorine evolution took place as well. Table 2.1 illustrates the various flow parameters of interest.

(45) TABLE-US-00004 TABLE 2.1 Current Density [mA/cm.sup.2] 150.0 Electrolyte Flow Rate through the Anode [ml/min] 300.0 Anode Flow Rate Normalized for Interface Area 14.29 [ml/(min .Math. cm.sup.2)] = [cm/min] Anode Flow Rate Normalized for Applied Current 95.24 [ml/(min .Math. A.sub.av)] Anode Flow Rate Normalized for Applied Average Current 2.0 Density [(ml .Math. cm.sup.2)/(min .Math. A.sub.av)] = [cm.sup.5/(min .Math. A.sub.av)]

EXAMPLE 3

CoP Plating, Loss of H3PO3

(46) For Example 3, the plating set up and plating conditions described in Example 2 were used including a commercial electrolyte for depositing fine-grained CoP alloys available from Integran Technologies Inc. (Toronto, Ontario, Canada) containing H.sub.3PO.sub.3 as the P source. The workpiece was a mild steel plate. The anode inserts had an effective interfacial area of 21 cm.sup.2 and the average current density applied was 150 mA/cm.sup.2 (300 mA/cm.sup.2 peak, 50% duty cycle) and the electrolyte was preheated to 80 C. and circulated through the anode at 300 ml/min; the resulting deposit thickness was 280 microns.

(47) The H.sub.3PO.sub.3 concentration in the electrolyte was determined analytically and the drop in H.sub.3PO.sub.3 after 4.73 Ah of plating is displayed in Table 3.1. The data indicate that, with the exception of the consumable Co anode on a polymer foam carrier (average grain size 70 nm, 388 VHN), the H.sub.3PO.sub.3 loss experienced was higher than expected when the consumable Co anode used a carbon-graphite substrate and the highest when a graphite DSA was used. The two electrodes experiencing the high H.sub.3PO.sub.3 loss also anodically generated chlorine gas. While anodic Cl.sub.2 gas evolution was expected for the graphite-DSA, it was somewhat surprising in the case of the Co on graphite anode insert. It was noticed, however, that the Co is preferentially dissolved close to the work-piece/absorber/anode interface, and, as soon as any graphite substrate is exposed, the anodic reaction was not limited to Co oxidation but included Cl.sub.2 evolution as well.

(48) TABLE-US-00005 TABLE 3.1 Co layer on Expected Open Cell Open Cell Co layer on H.sub.3PO.sub.3 loss Graphite Graphite Perforated based Foam Foam Polymer on P content in Active Anode: (DSA) (DSSA) (DSSA) the coating Loss of H.sub.3PO.sub.3 35.7 11.9 4.8 4.6 concentration in the electrolyte after 4.73 Ah of plating [%]

(49) In addition the cathodically deposited coating was characterized at three locations throughout the deposit thickness, namely the base (directly adjacent to the substrate), the center of the coating, and the outside surface (top). Table 3.2 provides data on cell voltages and coating characteristics for various active anode materials. The results highlight that the most uniform coating is achieved with consumable anodes according to the present invention.

(50) TABLE-US-00006 TABLE 3.2 Coating Coating Coating Outer Base Center Surface Graphite Open Cell Cell Voltage [V] 5.7 4.9 4.8 Foam DSA (prior art) Coating P [%] 1.41 1.23 1.12 VHN 525 496 485 DSSA: Co on Graphite- Cell Voltage [V] 2.5 2.5 3.5 Open Cell Foam (80 C.) Coating P [%] 1.43 1.36 1.31 VHN 532 531 525 DSSA: Co on Perforated Cell Voltage [V] 2 2 2 Polymer Plate (this Coating P [%] 1.40 1.41 1.39 invention) VHN 532 531 531

(51) Similar results are obtained when using Ni and/or Fe based electrolytes as well as for any other P-bearing alloys.

EXAMPLE 4

CoP Plating: Deposit Properties as Function of the Pump Speed @ 150 mA/Cm2

(52) For Example 4, the plating set up and conditions described in Example 3 were used including a commercial electrolyte for depositing fine-grained CoP alloys available from Integran Technologies Inc. (Toronto, Ontario, Canada) containing H.sub.3PO.sub.3 as the P source was used. The workpiece was a mild steel plate. The consumable anode inserts comprised a layer of Co on a perforated polymer (Nylon) plate and had an effective interfacial area of 21 cm.sup.2. The Co layer in the consumable anode (DSSA) had a hardness of 38733 VHN and an average grain size of 70 nm. The average current density applied in all trials was 150 mA/cm.sup.2 @ 80 C. and the plating time was 90 minutes. The total electrolyte solution for all trials was 1.7 liters and the electrolyte was circulated through the SA at various flow rates as indicated in Table 4.1 which displays selected cathodic deposit properties as function of the electrolyte flow rate through the consumable anode.

(53) The data indicate that flow rates through anode 150 ml/min produced the cathodic deposits consistent with tank plating deposits (1.50.5% P, 54025VHN). At a flow rate through the anode of 75 ml/min a coherent deposit was formed, however, the initial P content was only 0.9% and it dropped to 0.1% over the 90 minutes the plating took place. For flow rates at or under 37.5 ml/min no coherent deposit was even formed. The surface of the steel substrate after the plating appeared black and grey and no significant visible deposit was noticed in the cross-section. Flakes were noted during these runs to come off the surface and be brushed away by the motion of the anode applicator.

(54) This experiment reveals the importance of the anode design and anode flow rate through the DSSA insert to achieve similar deposits as obtained in tank plating in the presence of a large excess of electrolyte.

(55) TABLE-US-00007 TABLE 4.1 Anode Flow Rate Anode Flow [ml/(min .Math. cm.sup.2 Anode Flow Anode Flow Coating P Hardness Rate interfacial Rate Rate [%] [VHN] [ml/min] area)] [ml/(min .Math. A.sub.av)] [cm.sup.5/(min .Math. A.sub.av)] (Start/End) (start/End) 1.65 0.08 0.524 2.75 N/A - No N/A coherent deposit 16.5 0.79 5.24 27.5 N/A - No N/A coherent deposit 37.5 1.80 11.90 62.5 N/A - No N/A coherent deposit 75 3.59 23.81 125 0.90/0.13 410/387 150 7.18 47.62 250.0 1.43/1.39 540/536 300 14.29 95.24 500.0 1.40/1.39 532/531

(56) Similar results are obtained when using Ni and/or Fe based electrolytes as well as for any other P-bearing alloys.

EXAMPLE 5

NiP Plating, Polarization Curves DSA, DSSA

(57) For Example 5, the plating hardware described in Example 1 was used. The workpiece was a mild steel plate. The anode inserts had an effective interfacial area of 19.7 cm.sup.2. DSA and NiS based consumable anodes (DSSA) were employed. Open cell graphite foam was used as DSAs and perforated Ni plates (250 ppm S, 275 VHN, ratio of total area/interfacial area 1) were used as consumable anodes. The electrolyte flow through the anodes was 300 ml/min and the mechanical arm was operated at 50 strokes per minute. Polarization curves were obtained using the Internal Resistance Free Measuring System IRF-PS155AL available from Rosecreek Technologies Inc. (Mississauga, Canada). FIG. 5 illustrates the IR-free cell voltages for DSA and SA at 30 C., 60 C. and 70 C., respectively. As expected, the anodic reaction for DSAs is oxygen evolution. The polarization curve at 30 C. indicates that consumable Ni anodes at low current densities (<25 mA/cm.sup.2) anodically oxidize and dissolve Ni, at current densities between 25 and 75 mA/cm.sup.2 both Ni oxidation and O.sub.2 evolution occur, and finally at current densities >75 mA/cm.sup.2 the predominant anodic reaction is oxygen evolution. Raising the operating temperature from 30 C. to 60 C. and 70 C. extends the predominant anodic Ni dissolution range from 75 mA/cm.sup.2 to >250 mA/cm.sup.2. The limiting current density for anodic Ni oxidation can be extended by various means including, but not limited to: increasing the temperature, increasing the effective anode surface area, adding S to the Ni anode, increasing the electrolyte flow through the anode and employing an electrolyte not susceptible to Ni passivation such as the employ of chloride-based electrolytes.

(58) 1.7 liters of a chloride free electrolyte for Ni was employed with the following composition: 300 g/l NiSO.sub.4.7H.sub.2O; 40 g/l H.sub.3BO.sub.3; 0.1 g/l H.sub.3PO.sub.3; 4 ml/l NPA-91. Electrolyte temperature: 30, 60 C. and 70 C. pH: 2.5

(59) Extended plating runs were performed as well at 60 C. and 130 mA/cm.sup.2 average current density. It was noticed that the P content in brush plated deposits was much higher (up to 5 times) of what was obtained under identical conditions in a tank and the average grain size much smaller. Samples plated using DSA showed a much more pronounced loss of P with increased plating time when compared to deposits plated using DSSA which suggests that direct anodic oxidation of H.sub.3PO.sub.3 took place.

EXAMPLE 6

Fe Plating, Polarization Curves DSA, DSSA

(60) For Example 6, the plating hardware described in Example 1 was used. The workpiece was a mild steel plate. The anode inserts had an effective interfacial area of 19 cm.sup.2. DSA (perforated graphite plate) and Fe-based consumable anodes (loose Fe chips) were employed. In this experiment no binder was employed in the DSSA as the total amount of Fe anodically dissolved amounted to <10% of the overall active anode material weight. The electrolyte flow through the anodes was 300 ml/min and the mechanical arm was operated at 50 strokes per minute. Polarization curves were obtained using the Internal Resistance Free Measuring System IRF-PS155AL. FIG. 6 illustrates the IR-free cell voltages for DSA and DSSA at 26 C. The anodic reaction on DSAs was predominantly Fe.sup.2+ oxidation. Using consumable Fe anodes the anodic reaction was the dissolution of Fe.

(61) 1.7 liters electrolyte was employed with the following composition: 400 g/l FeCl.sub.2.4aq; 70 g/l AlCl.sub.3.6aq; 20 g/l MnCl.sub.2.4aq. Electrolyte temperature: 26 C. pH: 0.5.

EXAMPLE 7

Fe Plating, Deposit Properties DSA, DSSA

(62) For Example 7, the plating hardware and electrolyte described in Example 6 was used. Fine-grained Fe coatings were deposited at room temperature on mild steel plates using a DSA (graphite foam) or Fe-based consumable anode (electrolytic Fe chips) to a total thickness of 100 m. In this experiment, too, no binder was employed in the DSSA as the total amount of Fe anodically dissolved amounted to <10% of the overall active anode material weight. The exposed anode surface area was 12.5 cm.sup.2. The electrolyte flow through the anodes was 300 ml/min and the mechanical arm was operated at 50 strokes per minute. Table 7.1 illustrates selected process and coating property information.

(63) TABLE-US-00008 TABLE 7.1 electrolytic Fe anode (DSSA) DSA Current Density [mA/cm.sup.2] 340 340 Cell voltage [V] 4.3 5.4 IRF Cell voltage [V] 0.58 1.35 Cathodic Current Efficiency [%] 86 77 Overall Thickness [m] 115 97 Plating Time [min] 19 19 Appearance bright all over bright with a fringe of dark nodules microcracking density [number 110-160 90-120 per 10,000 m.sup.2] Hardness [VHN] 575 580 Average Grain Size [nm] 7 8

EXAMPLE 8

NiFe Plating, Fe3+ Bath Concentration

(64) For Example 8, the plating hardware described in Example 1 was used including a commercial electrolyte for depositing fine-grained Invar alloys available from Integran Technologies Inc. (Toronto, Ontario, Canada). The workpiece was a mild steel plate. The anode inserts had an effective interfacial area of 306 cm.sup.2 (77). DSA (perforated graphite plate) and consumable anodes (DSSA) having a consumable Ni-anode section and a consumable Fe-anode section on an open cell polyurethane substrate which were not electrically connected were employed, as indicated in FIG. 2. The Ni and Fe anodes were applied to the foam substrates by electrodeposition, the average grain size for the consumable Ni layer was 20 nm and for the Fe layer 5 m. The electrolyte flow through the anodes was 20 l/min and the mechanical arm was operated at a stroke speed of 0.17 m/sec. The electrolyte temperature was 55 C. and the applied total average cathodic current density 65 mA/cm.sup.2 (70% duty cycle, 100 Hz) using one or two Dynatronix Inc.'s Model PDPR 20-30-100 pulse power supplies (Amery, Wis., USA). In the case of the use of a DSA Ni and Fe ions were continuously replenished by suitable bath additions.

(65) In the case of using consumable anodes, a first power supply provided current to the consumable Ni anode and the steel substrate and a second power supply provided an equal current to the consumable Fe anode section and the cathode. The average Ni-anode current and Fe anode current were kept equal to adjust for the intended deposit composition of Ni-50% Fe. In this case several power supplies are used, the negative leads of all of them are connected to the workpiece to provide the total desired cathode deposition current. The positive lead of each power supply is connected to one of the distinct, electrochemically active consumable anode sections and the individual currents are set and/or regulated to achieve the desired anodic dissolution from each of the distinct segments as desired/required. In the case of alloy deposition, e.g., Ni.sub.(1-x)Fe.sub.x alloys the Ni.sup.++-ion and Fe.sup.++-ion concentrations in the electrolyte can be maintained at the desired levels by applying (1x)-fraction of the total current to the consumable Ni anode layer and the remainder, the (x)-fraction of the total current, to the consumable Fe anode layer.

(66) FIG. 7 shows the Fe.sup.3+ concentration in the electrolyte as a function of Ah/l of plating time. Between 0 and 2 Ah/l DSA and suitable Ni.sup.++ and Fe.sup.++ ion bath additions were employed, between 2 and 3 Ah/l consumable NiFe anodes without any bath additions were employed. The figure indicates that using DSA the Fe.sup.3+ concentration in the bath rapidly increases from 10 to 32%. When switching to consumable anodes the Fe.sup.3+ concentration rapidly drops again illustrating the benefits of using the consumable anode.

(67) The negative impact of the high Fe.sup.3+ level in the sample made with the DSA was seen in the appearance of the cathodic deposit. The deposit prepared using the prior art DSA was highly stressed and brittle while the deposit produced using consumable anodes (DSSAs) was bright, uniform and ductile.

(68) Based on the teachings provided herein, the person skilled in the art will know how to extend the operation from one consumable anode insert providing one element which anodically dissolves to a consumable anode insert with two or more elements. As highlighted, the electrochemically active consumable anode material can be provided for as alloy, as graded or layered material or, alternatively as highlighted in this example, the consumable anode insert can contain two or more distinct electrochemically active consumable anode material zones which are electrically isolated from each other that can be individually controlled using different power supplies.

(69) The foregoing description of the invention has been presented describing certain operable and preferred embodiments. It is not intended that the invention should be so limited since variations and modifications thereof will be obvious to those skilled in the art, all of which are within the spirit and scope of the invention.