Zinc Dichromate Finish ?

[M W.]

Hi all,

Does anyone know who sells a Zinc Dichromate dip to use on the lower portion of my 64 carburetor? I have tried Eastwoods spray and it doesn't look right. Too thick. Any help would be greatly appreciated.

Thanks,

Craig Willetts
#36551

[John M.]

Re: Zinc Dichromate Finish ?

Craig,

Unfortunately, the chromate dip only works well on fresh, unoxidized zinc. using the chromate dip on an old carb, will not work very well. I usually media blast the part, plate the pot metal with a thin layer of zinc, and then dip the part as soon as it has come out of the rinse from the plating tank. Zinc reacts very rapidly with the air to form a zinc oxide layer on the part. Once this layer has formed, the effectiveness of the chromate dip will be much less. The chromate reacts with the zinc to form zinc Dichromate, which is a much more corrosion resistant surafce.

Try Caswell plating for several different color combinations of the chromate dip, and associated plating chemicals. I would think that unless you are willing to setup a plating tank, you will probably not be satisfied with the results of simply dipping the carb. You will probably be better served by sending the carb body out for coloring by one of the carb restorers. If you can get the carb extremely clean and bright, you could get the dip to react properly, but this usually requires a media tumbler or vibrator to clean the casting. Either way you go to get the dip to work, it entails spending substantial ammounts of money for equipment, and unless you are doing other work with the equipment, it will not make financial sense.

Regards, John McGraw

[M W.]

Where to go for Carb Restoration? *NM*

[Patrick H.]

Re: Where to go for Carb Restoration?

I just sent two here:

www.customrebuiltcarbs.com

[Gerard F.]

It is a tedious process

Craig,

To do a carb body. The 67 carb body in the picture is is just coming out of the Caswell yellow dichromate dip for about the 2nd or third time. The prep was bead blasting followed by a dip in a light solution of muriatic acid, spray off with distilled water, then the dip in the Caswell solution.

I agree with John in the post above, except that with pot metal you would only replate with zinc as a last resort. First, if replated, the pot metal would come out too gold looking, and second, it would be almost impossible to get an even coat of zinc on the carb body with all the crevices and uneven surfaces. I even had to resort to coating parts of the body with Caswell Zincate solution prior to the dip where there was too much aluminum or magnesium in the pot metal, and where the dichromate would not take.

However, it didn't come out too bad:


They call that gold iridescent finish on the pot metal

Unless you are ready to spend lots of money, and trial and error time, on a Caswell kit, and have lots of other things to plate, it would be easier to send it out to one of the carb restoration specialists. I think the going rate is about $300.

I'm just a hobbyist, and having fun.

Jerry Fuccillo
#42179

[Joe L.]

Re: It is a tedious process

Jerry-----

That one came out better than Holley got it on most original carbs they manufactured. Often, original carbs will have some obvious "mottling" and "unevenness" to the coloring.

[John M.]

Re: It is a tedious process

Jerry,

You are correct that plating is the last resort for pot metal. That being said, I have finally gotten the plating process down for pot metal castings with lots of nooks and crannies. The secret is lots of agitation, higher current, and several anodes in the tank. I have a pretty substantial submersible pump that keeps the solution really churning. Like you, I would rather spend hours of my time, and countless dollars doing it myself rather than sending it out!
I am a hobbiest, and I do this stuff for self-satisfaction. I get no satisfaction out of sending parts out to be restored.

Thanks for the tip on Zincate, I never thought that some of the problems that I have had with pot metal may have come from a high aluminum content!

Regards, John McGraw

[Gerard F.]

Re: It is a tedious process

John,

Just brush the Zincate on full strength or a strong solution, in the areas of pot metal, where the dichromate is coming out spotty, then clean it off. It replaces the aluminum with a coat of zinc, and then will take the dichromate.

On my carb, the area of the air horn with the part and list number, came up spotty, so I had to come up with something. Kind of works like a primer.

Jerry Fuccillo
#42179