Metal finishing Q&As since 1989

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Durable Chem-Film Coating

2006

Hello,

I've designed an alum. computer Chassis and would typically Chem-Film gold this product but have noticed the lack of durability of the surface finish (i.e.- easy scratching, etc). Someone in our organization mentioned Gold Anodize instead but I'm not to hip on that end appearance. Does anyone know of a process that would provide my standard MIL-C-5541E, CL3 gold appearance while adding significant durability and expected electrical conductivity?

Thanks!

Bryan Ridgely
chassis plans - San Diego, California, USA

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First of two simultaneous responses --

I think anodising will be your best choice. What specifically about the appearance of anodising don't you like? Is it the lack of iridescence?

There are lots of different coloured dyes you can get, so it should be possible to get something at least close to the colour of the chemical conversion coating.

John Reid
- Brisbane, Qld, Australia
2006

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Second of two simultaneous responses --

1. A company in Atlanta, for over 35 years, on chassis, used Class 3 aluminum chromate and topped off with water dip acrylic (several proprietary commercial names end in "lac"). When electrical contact was needed in assembly, they just scratched away the acrylic.

2. If the above is not close enough to your desires, then consider tin plating the aluminum and dipping the plated tin through a very weak chromium, salts solution (it will not "convert" but the residue will retard corrosion sufficiently). Electrolysis NIckel would be be better for corrosion but the tin would be better for lower voltages.

Robert H Probert
Robert H Probert Technical Services

Garner, North Carolina

2006

Thanks for the help everyone!

Bryan Ridgely
chassis plans - San Diego, California, USA
2006