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No L.C.D. coverage problem in acid zinc plating

Q. Hello everybody,
We are doing acid zinc barrel plating on nuts and bolts. I operate the bath at 30 gms/ltr zinc metal, total chlorides 120 gms/ltr and boric acid is 30 gms/ltr. When the bath is new I was getting load within 30 min, and nuts appeared very bright. Nut inside also appeared bright finish. After 15 days the load comes late and dull finish. Inside the nut appears black. Then I consulted my chemical supplier, they says that give zinc dust ⇦ this on eBay or Amazon [affil links] treatment; he was perhaps right. - Peroxide treatment may remove some brighteners, which may account for a need for additional brightener; so his third guess may have been right.

Me, I certainly guess that the darkness and lack of coverage is poor LCD coverage rather than iron contamination but ...

...after 3 guesses by telephone and still poor plating, it is long past time for a tech service person from the supplier to be on-site helping you and right now. If he is not on his way, you should be finding a new supplier who is willing to do what he is supposed to do for his premium :-)

Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 12, 2008