Topic: Zinc di-chromate at home?

[Murf]

Like most who keep their cars for a long time, there are some items that were zinc dichromate at one time but have for various reasons lost their former nice color and now are either almost down to the zinc or look very faded and not professional looking.  The zinc is still a good coating, it is the dye that gave the gold tint that has become thin.  Is it possible or practical to recolor those parts at home?  If so where does one get the solution.  The plating company I use calls it "egg dye" but always complain about EPA regulations when I ask them to "color" as they call it, parts entrusted to them for rehab.  Has anyone any inside knowledge of what products or products are used to "color" an already zinc plated part to make a Dichromate finish?  There was a question about coloring carbs here at one time but it did not go anywhere.  Just something that has bugged me for some time and hope that someone has fought this battle and will share their experience and solutions.  Anybody care to chime in?

[Mike Bauman]

Hi.....back in the day I messed around with a product from Caswell electro plating. .... I will look tomorow to see if I have any contact info....Mike

[rockhouse66]

John
I have used the Caswell Dichromate with success on freshly zinc plated parts and sometimes on new parts that you buy that are zinc coated.  I doubt it will do much for you on "old" zinc, though you can clean the part with carb cleaner and try it.  It seems to need a fresh zinc coating to do whatever it does to "take" the color.  I also am guessing that some new parts you buy are some sort of zinc electroplated (really smooth surface) and it doesn't seem to "take" to that either.

BTW, they say to blow dry it after treatment, but I use a heat gun to dry it and it really seems to bring out the rainbow effect.

This is the stuff I use:
http://www.caswellplating.com/electroplating-anodizing/zinc-plating-kits/chromates/yellow-chromate.html

[Toploader]

Maybe you should give the idea of messing around with this stuff at home a second thought.

From the http://www.thecarburetorshop.com/

Chromate

The chromate treatment is a cold treatment applied to zinc alloy castings. The castings are first chemically cleaned in caustic lye; washed in water to neutralize the lye which is a “base”; and then dipped in a solution of nitric, sulfuric, and chromic acids. The surface of the zinc alloy is chemically “etched”, and the residue is a very thin cover coat, which is a greenish goldish cover. This process is done to minimize the formation of zinc oxide of the metal. WARNING! This is not a process that the hobbyist should even consider!!! The active ingredient, chromic acid, is a known carcinogen! THIS STUFF IS DEADLY.

Conclusion – and advice to the hobbyist! We evaluated the cost, convenience, and danger of these chemicals long ago. We feel that, even with the number of carburetors restored by The Carburetor Shop, that that number is insufficient for us to attempt to do any of the electroplating and/or chromate coatings ourselves. We send everything to various “metal laundry” companies for this service. We highly suggest that hobbyists should consider doing the same. This article is placed on the web to discuss what finishes the restorer should be aware of (for points judging and protection); NOT as a do it yourself treatise.

[Bob Gaines]

Mike Ulrey and Jon Ernhart both carburetor guys and both died of brain cancer. Coincidence or from the zinc dichromate bath? Myself as well as others have wondered.

[J_Speegle]

I've purchased the zinc dichromate concentrate but have not put it to use. Opened the bottle and the fumes would drop you to your knees and I've breathed in ALLOT of nasty biochems in my life. Think I'm going to keep having shops do mine. Would consider doing zinc at home but as long as I'm not doing  the dichromate bath might as well have them do both IMHO.

There were some people doing everything in zinc dichromate to save money then removing the dichromate dye with a bath but have not tried that as of yet.

Also found that if I left the zinc dichromate exposed to the air it can flash and loose it color so I've started oiling it and bagging/wrapping to maintain the color until I use all that hardware and parts. I've got extras (always do 2-3 of everything when I plate) that have been around for 20 years or so

[CW4macret]

Eastwood offers a 3 spray can do it yourself Zinc Di-chromate paint kit. I have the kit but have not tried the process yet. I will give it a try this weekend

[carlite65]

i have seen those. it looks like what it is.....paint. i didn't care for the look at all.

[Bob Gaines]

i have seen those. it looks like what it is.....paint. i didn't care for the look at all.

+1. looks best when used on very small parts but still not good enough. Or from far away .