Carter Carb Rebuid - Caswell refinishing Copy Cad

[Misdemeanor]

The first step in what is sure to be a long restore project will be the carb. I decided to do something small as a meaningful first step. I tore the carb apart and ordered a Caswell Copy Cad plating chemicals. I didn't but the kit just the Copy Cad chemicals and yellow chromemate. So far it has worked out well. The carb body was glass beaded and a quick dip in 5% muriatic acid rinse and 15sec dip in the chromate dye. The other metal parts got glass beaded and then zinc plated and then dipped in the dye. The colors came out close to original, I think. I was afraid the carb body would come out too bright but it returned to a greyish brown yellow that looks original based on the protected areas I observed before blasting. The pics below show the carb body in the white and after using the Yellow Chromate dip. The metal parts are a brighter yellow but again I think this is correct.

 

[dougimes]

Dave,

When you say zinc plated, do you mean electrolysis type plating or just chemical dip?

 

[Misdemeanor]

The Caswell Plating is a process that is true zinc electroplating. The kit comes with the chemicals create a bath that efficiently allows the current to flow from a sacrificial zinc plate (neg)(99% pure zinc) to the part (pos). Once a part is plated with zinc it is dipped in the chromate dye. The dye absorbs into zinc, without zinc the chomate dye just washes off. With that said, the cast aluminum has some zinc content. It isn't pure aluminum. It is my understanding that the aluminum can be zinc plated in addition to the zinc it already has but based on my limited research this wasn't done in the original manufacturing process. The aluminum was just chromate coated and the chromate reacted to the zinc in the casting. I did the following....

Aluminum parts -
1. Cleaned with standard carb solvent.
2. glass beading
3. full degrease with brake cleaner.
4. Dip in hydrochloric 5% Water 95% for about 5-10 sec.
5. Rinse with R.O. Water
6. Dip in Caswell Chromate dye yellow. Note - Black and OD available.

The above process created what I think is the original color based on what I observed under the unexposed gasket areas before bead blasting. From what I have read a more modern restore would require a zinc plating to the aluminum before chromate. This should create a bright yellowish finish on the aluminum. I think it would base on some experience I did over 30 years ago when restoring carbs on 60-70's Mopar carbs with products similar to Caswell. Not what we want on a military restore.

Metal parts -
1. Cleaned with standard carb solvent.
2. glass beading
3. full degrease with brake cleaner.
4. Zinc plate - 1.5-2 volts. Current adjusted enough to see bubbles forming like foam on the surface. 15min.
5. Rinse with R.O. Water
6. Dip in Caswell Chromate dye yellow. Note - Black and OD available.

Metal parts are the same as aluminum but required the parts to be re-zinced since the blasting and years of corrosion removed all the original zinc plating. I'm not sure how shining the metal parts would have been originally. If you polish the metal before zinc plating you will get a more shinny plate. I choose not to polish but I think a slight polishing would have yielded a more accurate finish. The stamped out part originally wasn't polished but I think the natural finish of a new stamping wouldn't have been matte like my bead blasted parts. If I do anything over I would polish the metal parts to a sheen and then zinc plate.

Below is the finished results

 

[Misdemeanor]

I did some testing in a salt exposure. I place a bare metal bolt, a zinc plated bolt and a zinc plated chromate bolt in the water softner brine tank for about a week just above the water line. The bare bolt is showing extreme surface corrosion. The zinc is turning a bit chalky and the chormate one is a little less chalky. My conclusion is the zinc plating has significant corrosion resistance but the chromate does little to nothing and is purely cosmetic. Long term under natural exposure the chromate might have some value but my test was a rapid exposure test so take if for what is is worth. I didn't test any aluminum but I am thinking about doing that next.

 

[clinto]

Very nice work and attention to detail. Thanks for taking the time to share.

I always wanted to try this when I was in the Mopar hobby, but I had a friend who had an in for replating (phosphate, zinc, cad, etc.) so when I did a 100% job, I just bagged everything and sent it out.