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Tin/zinc plating has poor appearance
Q. Hi,
We currently plate small parts made from annealed steel (heat treated)with a 70% tin 30% zinc plating, along with hex chromate for good corrosion resistance. However, we would like to get a more appealing appearance to the final product. Can anyone recommend anything that can go on top of the tin/zinc/chromate plating to give it a more brilliant appearance? For example, is it possible to put a layer of shiny Nickel or some other plating as an appearance layer? Ideally we would like to achieve a shiny gold or silver appearance (without the use of Cadmium).
Any suggestions would be greatly appreciated!
Thanks,
Joe Tratner- Bartlett, Illinois
A. Tin/Zinc has an industrial finish and is not a bright deposit. You could plate bright Zinc on top but you would lose the excellent corrosion resistance of the coating. Since the deposit is soft you could burnish the coating in a vibe-barrel with the right media and than chromate.
George Shahin
Atotech - Rock Hill, South Carolina
Q. I'd like to add a bit more information to my original question. Our overall goal is to plate the annealed steel with a plating that is very resistant to corrosion in salt water. To add to the difficulty, it must also look good (i.e. bright silver or Gold).
We wish to do this with environmentally acceptable products (no Hex chromate or Cad). We looked at Trivalent Chromate on top of the tin/zinc and it looks pretty bland. So, we are wondering if we can put something on top of that? OR would Electroless Nickel on it's own be as corrosion resistant as the tin/zinc/chromate combination?
Thanks again.
Joe Trattner [returning]- Bartlett, Illinois, USA
A. I don't think you'll be able to apply any plating on top of the chromate, but you may find a tinted lacquer you like if conductivity is not a problem. Are you sure you need tin-zinc? It's a great finish but, as you say, unattractive. A regular zinc plating with a clear or black chromate would be better looking.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
A. High phosphorous electroless nickel would be an excellent choice for your application.
Dan Weaver- Toccoa, Georgia
Thanks to everyone for the suggestions. I really appreciate it! I will look into some of the options suggested.
Q. By the way, Where would I look for a tinted lacquer? Do platers normally offer that service?
Thanks again,
Joe Trattner [returning]- Bartlett, Illinois, USA
A. Hi Joe. Although there are air-dry solvent based lacquers that can be tinted, another possibility is CED (cathodic electrodeposition) electrocoating, also called electrophoretic lacquer.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Tin-zinc plating is not smooth enough
Q. I am QE at an automobile parts manufacturing plant and very un-familiar with plating processes; we just received a complaint from a customer where he claims Tin-Zinc plating is not conforming as the paint coat he's applying is not as smooth as typically is and also it failed the peel off test. Is it possible the plating process to provide uneven surface?, What could be the cause of a uneven plated surface?, under microscope the suspect parts (oil temperature sensor) looks like if a "mini blizzard" stroke it. My last question is, How can I verify smooth plated surface, besides microscope?.
Thanks for your help and advise.
Quality Eng. - Hidalgo, Texas
March 3, 2015
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