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Extreme LCD problem, Ni strike & Ag cyanide don't cover
Q. I am plating an aluminum part (Al6101) that is U shaped and also has four peaks (with valleys) on the inside of the U shape. Cleaning and adhesion have not been an issue. Standard clean, etch, deox, zincate (single using CN Bondal). My sulfamate Ni strike and Ag strike are having troubling covering the valleys under the peaks inside the U shape.
I have already setup the Ni as follows; lowered Ni to 8 oz/gal, raised Cl to 8 oz/gal, keep pH 3.8-4.4, raised temp to 135 °F, strike for 2/3 mins @ 15/10 asf.
My Ag strike is 0.5 oz/gal Ag, 16 oz/gal KCN. Strike for 1 min at 5 asf.
Everything covers inside the U shape except a barely visible line that runs just under the peaks. All other parts without extreme LCD are plating fine. Any suggestions?
Plating Manager - Houston, Texas
October 16, 2025
A. Hi Lance.
It might be that you have gone as far as you can with the nickel strike. I would expect better covering power from a complexed cyanide-based solution than from a simple salt like the nickel strike. Have you tried simply skipping the nickel and doing the cyanide silver strike directly on the zincate?
If you can't cyanide silver strike, or cyanide copper strike, you may need a more complex answer like using an alkaline electroless nickel as the first step, or implementing auxiliary anodes.
If a pic is available (attach in e-mail to mooney@finishing.com), it might help.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
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