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Zinc trivalent blue plating problems.

February 4, 2011

1) If current is low or high then what is effect on plating.
2) If voltage is low or high then what is effect on plating.
3) If caustic and zinc metal low or high then what is the effect on plating.
4) If current density low or high what is the effect.
5) If pH is low or high in bath and passivation then what is the effect.
6) what is the contribution of plating thickness,Passivation , lacquer towards the corrosion resistance in terms of percentage.

What is difference between Clear passivation, Bleached passivation, Colour passivation, Olive drab passivation, and Black passivation.

Darshan Vernekar
plating shop employee - Bangalore, India

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February 4, 2011

Hi, cousin Darshan.

1). High current results in burning. Low current results in longer plating time. This is a superficial answer though because there can be many subtler effects on covering power, brightness, etc.
2). Voltage has no effect except its effect on current.
3). It is difficult to say exactly what ill effects will result from operating a bath out of spec; certainly burning if too little zinc or too little conductivity.
4). See #1
5). See #3
6). You can do a salt spray test for the lacquer to see how effective it is. In general, passivation protects against white rust and zinc plating protects against red rust. But if the zinc plating is bad, it's hard to count on the passivation to do anything because it works only on the zinc, not the underlying steel.

These days, where trivalent passivation is the rule, the difference in those chromates is mostly just dye. Sometimes black chromate has silver in it though. Bleached passivation is probably no longer applicable, as it used to be yellow hexavalent passivation that was soaked in hot water until most of it was gone.

I've yet to meet anyone who enjoys flash-card quizzes, especially public ones -- so I know you will get more and better responses if you phrase your inquiry in terms of the problems you may be having, rather than as a test of the reader's knowledge :-)

But if you are looking for a list of "If this problem, then check that", I think the Canning Handbook is a good choice. Good luck.

Regards,

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

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Hello Mr Mooney!

Methinks your patient and painstaking reply to your country cousin details it better than the good old Canning book!

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

March 19, 2011