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  for Metal Finishing since 1989
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Coating for aluminium

We are looking for a coating on aluminium connector bodies (6082) which will withstand 500 hrs minimum salt fog test, can be applied with precise thickness - especially on threads, and where adhesion is guaranteed. The coating should be jet black (other colour possibilities very useful) Maximum depth of 30 micron. Lubricity would be an advantage, however Teflon/nickel on the mating parts covers this.

Pat Crossan
Engineering and Design - Cork, Ireland
2002

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First of two simultaneous responses --

With careful preparation of aluminum for plating, a high phosphorus electroless nickel 25 microns followed by a mid phosphorus electroless nickel deposit containing sulfur. sulfur compounds are often used as stabilizers in mid phos electroless nickel solutions. Followed by a short dip, 30 to 40 seconds, in 1:1 nitric acid until a black color apears. The black is a result of etching leaving sharp holes and dendrites that absorb light creating the black color. The black will not wipe off.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2002

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Second of two simultaneous responses -- 2002

Pat,

You can have EN blackened. It's not uncommon and fits every aspect of your search (except just two colors, natural and black).

Bye,

Guillermo Marrufo
Monterrey, NL, Mexico