Color plating of chrome sockets - what's the process?

A. This could be either interference coloring or PVD coatings, e.g., gold-colored TiN. See 'Special Finishes for Stainless Steel' available from the SSINA: http://www.ssina.com/publications/spe_fin.html

Interference coloring on stainless, also called INCO coloring, can be produced by anodizing in a hot sulfuric-chromic acid mixture. Colors arise from the interference between the light reflected off the metal and the light reflected from the transparent oxide surface; different thicknesses in the range 70-400 nanometers give different colors.
Interference coloring is not as available as PVD coating. B&M Finishers / Prismatic Stainless Steel [a finishing.com supporting advertiser] in NJ advertises both 'Prismatic' and 'Ti-Gold' Stainless Steel.'
Russamer Lab interference color anodizes Ti, Ta and Zr, so probably can handle stainless, too (commercial accounts, only).

If interested in the process, find the Internet article: 'Chemical and electrochemical coloration of stainless steel...'
This same Brazilian group has a follow-up paper using only 5M sulfuric acid electrolyte (no chromic) at 50 °C:
'An Environmentally Friendly and Practical Method for Obtaining Color on Stainless Steel by Interference,'
J. Electrochem. Soc., Vol. 152, Issue 11, pp. B491-B494 2005.

A. Ken's replies are always well researched and usually right. But in following the link from Glen, I see a claim from Harbor Freight that these are chrome-vanadium tool steel with "durable electroplate".

Someone would have to examine them close up to know for sure, but from this claim I think they are nickel plated followed by electrophoretic lacquers of various tints. Another reason for this being my guess is that it would be significantly less expensive than PVD processes. Each color would take a separate tank, but I think only one e-coat tank would be required, and the additional colors obtained with a simpler 'post-dye' tank. I think a small shop could set up to do this on nickel plated items

P.S. to John. Without a picture of the lug nuts it's only a guess, but usually these are zinc plated with a blue or gold colored chromate -- and the colors are more pastel than saturated and vibrant.

A. If something can be proved, it need not be argued! Or so goes a saying.

John, please take those colorful sockets and subject them to solvent test. Dip them in MIBK overnight and then rub them aggressively with a cloth kept wet with MIBK. If the colors begin to wear off, you will know that the process is electrophoretic lacquer with a dye.

In case the colors are not affected, then it could be PVD / CVD.

I personally do not have much knowledge about Anodizing / Electrocoloring but I have seen that being done only on Aluminum.

Keep your fingers crossed that the color does wears off when you do the MIBK / solvent rub test.

A. Now I am more confident that they are nickel electroplated followed by a tinted lacquer. I believe it's electrophoretic lacquer, that is, deposited via electricity. I don't think there's enough evidence in the picture for us to say whether there is an additional clear coat on top of the tinted layer, but if you saw it, you saw it -- and polyurethane coatings on tops of e-coating are common. Despite the scratching, it seems like a pretty good product idea.

No, there is no galvanizing or electroplating process that would offer colors like this. To obtain this coating, apparently you should specify nickel plating followed by electrophoretic lacquering in whatever color you want. Good luck.

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

A. Hi Al. Metals are silvery or brass/gold in color, of course, not the colors of the rainbow. As far as I know, there are only three ways to get colors like that then: an organic coating process like electrocoating, or anodized aluminum which can absorb dyes into its porous honeycomb structure, or a clear oxide coating which yields diffraction coloration.

We appended your inquiry to a thread about colorful electrocoatings, which may help give you a feel for that approach. We have numerous threads about anodizing if you feel that anodized aluminum sprockets have applicability. The third approach, transparent/translucent oxide coatings for diffraction coloration could apply if the sprockets were made of stainless steel or titanium; I don't think they can be done directly on steel, but they might be possible on sputtered titanium coatings on steel. Good luck.

Regards,

A. Electroless nickel plating over Steel baked in a conventional oven to 400 °C for an hour will oxidize superficially and take rainbow colors. Perhaps not what you are looking for but very appealing in a way.

A. Well... An interesting take on this would be to make the sprockets out of Titanium and "Anodize" them. You can get most colors in the rainbow and they vary with the voltage applied.

A. Hi Dinesh. Your photo is small and low resolution, so I'm not sure what your components are or what they are made of. Hose couplings, socket wrenches?

Nickel plating followed by ED coating would be corrosion resistant, although it looks like some suppliers have had trouble keeping their colored sockets good looking for extended periods.

Regards,

A. Hi. You can probably go ahead with the process up through the nickel plating for rust prevention and wear resistance. But no organic coating that you can apply for color sounds very promising against the wear of a chain. I think you'll need some type of PVD coating -- perhaps titanium, subsequently anodized.

Regards,

Hi Cipko. The first I heard of it was in this question of September 25, 2006, so it was probably an original thought for you rather than something you had previously seen and forgot.

Regards,

A. Hi David. It appears that the coating on the sockets was electrophoretic lacquer (e-coating), and those nylock nuts look very similar (the reason they are brighter is probably that there is nickel plating on the nuts beneath the e-coating, and such nickel plating is probably quite a bit brighter than on the sockets.)

Luck & Regards,