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32% nickel plating on ETP copper wire
We've been plating about 5.5% nickel on copper /cadmium copper for years. Now we are trying to plate 32% nickel on copper, the intent is to get a min 27% nickel after the wire is drawn. Inlet ETP copper size is .038", bath is conventional nickel sulfamate, INCO 'S' nickel pellets, bath temp about 147° F , current density 90-100 ASF, filtration speed 75 l/minute
Degrease is a cathodic clean with 0.75% sulfuric acid + 1.% phosphoric acid,followed by a water rinse.
(I have to add here, we started this plating line 4 weeks back and at that time we used potassium cyanide for degreasing followed by a water rinse, we've been using cyanide baths for silver and have loved the KCN degreasing power)
Then a strike which is 250 gms/l of sulfamic acid ( yesterday we reduced this concentration to 12.5 gms/l), this is a dip strike, there are no anodes, but the wire goes wet into the main plating bath. Yesterday when we reduced the sulfamic acid in the strike tank, the wrap test was great, no cracking , we bent the plated wire, wrapped and un-wrapped, 5 hours later we stopped the machine to re-check, we had cracks again, its very erratic.
On the same machine we tried to plate 4% nickel on copper yesterday since the nickel was cracking on the 32%, we couldn't plate even 4% -- where could we be going wrong?
product designer - New Delhi, India
April 5, 2009
April 14, 2009
Some suggestions which may help: You should use an alkaline cleaner, reverse clean, 180° F, 100 ASF for at least 5-10 seconds, then pull the wire though a die to wipe, say .037", rinse, another die wipe .036" and then directly into the sulfamate nickel, no acid, no strike, enter the nickel bath dry from the die. This is a continuous process: clean, wipe, rinse, wipe, plate.
With S rounds you should not need any chloride or bromide.
Control pH 3.5 - 4.0.
You may be getting decomposition of sulfamate at 147° F. 115° F should be hot enough. Your current density seems low if you have strong agitation.
You should not lose any nickel during subsequent drawing, there should be no reason to plate higher than 27%.
Jeffrey Holmes, CEF
Spartanburg, South Carolina
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