Dev-Zinc Ni-alloy
Dev-Zinc Ni-alloy is an acid chloride based zinc-nickel alloy plating system utilizing ammonium chloride, boric acid, zinc chloride and nickel chloride in the electrolyte. The alloy deposited is bright over the entire current density plating range of 1 to 100 ASF. Parts plating with the Dev-Zinc Ni-alloy process are leveled and ductile.
The nickel content of the alloy will vary between 10 15% by weight, where maximum corrosion resistance is achieved. Generally, the range of nickel deposited is varies 2 to 3% over the current density range plated. This allows for maximum performance of the specially designed chromate conversion coatings for this process.
Dev-Zinc Ni-alloy can be used in either rack or barrel plating operations with either air or mechanical agitation. Where barrel plating is used, barrel rotation is sufficient for solution movement.
Specially designed chromate conversion coatings allow the deposit to be chromated in blue-bright, yellow and black conversion coatings. Trivalent and non-chrome black conversion coatings are available.
Operating Parameters:
|
|
Recommended |
Range |
Zinc Metal |
2.0 oz/gal |
1.7 2.2 oz/gal |
|
Nickel Metal |
3.5 oz/gal |
3.2 3.8 oz/gal |
|
Total Chloride |
25 oz/gal |
22 28 oz/gal |
Boric Acid |
3.0 oz/gal |
2.7 3.3 oz/gal |
Zinc to Nickel ratio |
1:1.8 |
1:1.5 1:2.0 |
|
PH |
6.2 |
6.0 6.5 |
|
Temperature |
105 oF |
100 110 oF |
Dev-Zinc Ni-alloy Carrier |
5% |
4 6% |
|
Dev-Zinc Ni-alloy Replenisher |
0.30% |
0.20 0.40% |
|
Cathode Current Density ASF |
5 25 ASF |
|
|
Anode Current Density ASF |
15 35 ASF |
|
Dev-Zinc Ni-alloy
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Make-up Procedure:
¨ Leach the tank with 1 to 2% Hydrochloric Acid if its new or has been used in other applications.
¨ Add about 1/2 of the volume with cold water to the clean tank. Warm the water to 90 100 oF to speed up the dissolution of the chloride salts.
¨ Add the Ammonium Chloride. The solution will cool. Allow it to return to room temperature before proceeding.
¨ Add the Zinc Chloride 50% solution, Nickel Chloride and Boric Acid.
¨ Adjust the pH with Ammonium Hydroxide to the pH range of 6.0 6.5.
¨ Add the appropriate amounts of Dev-Zinc Ni-alloy additives.
|
|
100 Gallons |
100 Liters |
|
Ammonium Chloride |
163 lbs |
43 lbs |
|
Zinc Chloride Solution 50% |
5.7 gals |
5.7 liters |
|
Nickel Chloride salts (NiCl2 * 6H2O) |
85 lbs |
22 lbs |
Boric Acid |
19 lbs |
5 lbs |
Ammonium Hydroxide (as needed to adjust pH) |
Approx. 8 gals |
Approx. 8 liters |
Dev-Zinc Ni-alloy Carrier |
5 gals |
5 liters |
Dev-Zinc Ni-alloy Replenisher |
1140 mls |
300 mls |
Control and Maintenance:
¨ Typical control of the additives is done by amp-hours. It may also be done by direct observation of the deposit, and use of a heated Hull Cell.
o Dev-Zinc Ni-alloy Carrier is typically added at the rate of 1 gal (3.8 liters) per 7,500 A-Hrs. Alternative method - add at the rate of 1.5 gals (5.7 liters) per 100 lbs (45.5 Kg) Ammonium Chloride. It refines the grain and extends the bright current density plating range of the bath.
o Dev-Zinc Ni-alloy Replenisher is typically added at the rate of 1 gal (3.8 liters) per 10,000 A-Hrs. It increases the brightness and leveling of the bath.
¨ Its highly advisable that before any adjustments are made in the organic additives, the temperature, pH, chloride, zinc and nickel be checked and adjusted within range.
Temperature
¨ Below the recommended range will cause the bath constituents to precipitate.
¨ Above the recommended range will cause excessive nickel to be deposited, particularly in the low current density areas.
pH
¨ Below the recommended range will induce brittleness in the high current density areas.
¨ Above the recommended range will cause graininess in the deposit and may cause some of the bath constituents to precipitate.
¨ Monitor with a pH meter regularly; raise the pH with Ammonium Hydroxide and lower it with Hydrochloric Acid.
Ammonium Chloride
¨ Its essential to the operation of the bath. The ammonium ion acts as an additive, resulting in brighter deposits as well as controlling the amount of nickel available for deposition.
Anode baskets
¨ Anode baskets for both the zinc and nickel should be constructed of Titanium. In rack installations, Dynel or polypropylene bags should be used.
Dev-Zinc Ni-alloy
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Zinc to Nickel ratio
¨ This number is very important since it affects the quality and appearance of the plate. The best ratio yields a deposit with 10 15% nickel in it.
¨ High nickel levels induce brittleness and the deposit becomes difficult to chromate.
¨ Low nickel levels result in a cloudy deposit and adversely affect corrosion resistance.
Anodes
¨ The most economical operation uses both Nickel and Zinc anodes in the bath. The ratio of nickel to zinc must be determined empirically after operating the bath, but is generally in a ratio of 1 anode nickel for each 2 to 3 anodes zinc.
¨ An easier to control operation uses Nickel anodes in the bath, and additions of liquid zinc chloride 50% - to control the Zinc concentration in solution.
¨ Inert anodes Iridium Oxide coated Titanium may also be used.
Agitation
¨ Agitation is extremely important in the alloy plating process. Air or cathode rod agitation are acceptable methods. The speed of the cathode rod will influence the alloy deposition and must be determined to insure the proper alloy is deposited.
Filtration
¨ Filtration is essential for plating quality. Suspended solids from anode sludge, iron salts, organic iron salts, etc. will cause roughness if not filtered. Filter media of 20 to 50 microns works well. The use of diatomaceous earth is highly recommended to facilitate the filtering process.
Zinc Analysis:
¨ Pipette a 1 ml sample of the bath into a 250 ml Erlenmeyer flask.
¨ Add 100 mls DI water .
¨ Add 20 mls pH 10 Buffer solution (70 g Ammonium Chloride, 570 mls conc. Ammonium Hydroxide, and DI water to dilute to 1000 mls) Mix well.
¨ Add 0.5 1.0 gr Sodium Cyanide and mix until the Sodium Cyanide is dissolved
¨ Add 0.1 gr EBT indicator. Color of the solution should be blue/green to violet.
¨ Add 15 mls 10% Formaldehyde or until the color changes to violet.
¨ Titrate with 0.0575 M EDTA a permanent blue color persists for at least 15 seconds.
Mls 0.0575 M EDTA x 3.75 = g/l Zinc
Mls 0.0575 M EDTA x 0.5 = oz/gal Zinc
Nickel Analysis:
¨ Determine by Atomic Absorption methods
Chloride Analysis
¨ Pipette a 1 ml sample of the bath into a 250 ml flask
¨ Add 50 to 100 mls DI water
¨ Add 5 mls 10% Sodium Chromate solution
¨ Titrate with 0.1 N Silver Nitrate to a reddish-brown end-point.
Mls 0.1 N AgNO3 x 3.55 = g/l Chloride
Mls 0.1 N AgNO3 x 0.473 = oz/gal Chloride
Dev-Zinc Ni-alloy
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Boric Acid Analysis
¨ Pipette 2 mls of sample into a 250 ml flask
¨ Add about 50 mls DI water
¨ Add 10 drops Bromocresol Purple indicator
o If the solution color is yellow-orange, add 0.1 N NaOH dropwise to a slight purple color
o If the solution color is purple, add 0.1 N HCl dropwise to a definite yellow-orange, then add 0.1 N NaOH to a slight purple
¨ Add 5 grams Mannitol powder and mix. Approx one heaping tablespoon
¨ Add one dropper of Phenolphthalein indicator.
¨ Titrate with 0.1 N Sodium Hydroxide to a slight purple end-point
Mls 0.1 N NaOH x 0.412 = oz/gal Boric Acid
DISCLAIMER:
The information presented herein, while not guaranteed, is to the best of our knowledge true and accurate. No warranty or guarantee expressed or implied is made regarding the performance of any products, since the manner of use is beyond our control. No suggestion for product use or anything contained herein, shall be construed as a recommendation for its use in infringement of any existing patent and we assume no responsibility or liability for operations which do infringe any such patents. The above includes confidential and proprietary information of Deveco Corporation and is furnished to you for your use solely on products or processes supplied by us to you.
Product data sheets/PZ063-PZ065 Effective date: 1-31-06 Supersedes: 4-7-05