Olive drab chromate over commercial zinc

[drdelano]

Hi, I just got a O.D. Chromate kit and called and talked briefly to Mike about how to apply it. Does anybody else have any experience with this? i'm trying to color commercially zinc plated bolts and screws for my '47 Willys, so that the bright zinc will not show. The original fasteners seem to have been originally relatively bumpy od color over red primer, and/or painted black. Is there some material that will not react with the solution that I can use to screw the little sheet metal screws into for the dipping/rinsing/curing in oven phase?

[seanc]

It sounds like you're just wanting to dip new bolts in the chromate? If so, I doubt you'll get what you're expecting.

The chromate dip needs raw zinc to react with. An already chromated bolt doesn't (shouldn't) have any exposed raw zinc. You would need to strip the existing chromate layer off first. And even that may not give satisfactory results.

I tried many times to re-chromate commercial bolts, and it didn't work well at all. Commercial bolts aren't plated very thick. Plating and chromate thickness are inconsistent. By the time I was sure all the old chromate was gone, some of the zinc layer had been stripped as well. If I made sure not to over strip the zinc, some of the old chromate remained. Either way looked terrible.

It just wasn't worth it. It's far easier and better to completely strip the bolt, re-plate it, then chromate it.

[drdelano]

Thanks for the help. Can I strip the zinc off new commercial fasteners by just using muratic acid? or do you somehow reverse plate them? Is "copycad" a good surface? or does it have to be zinc?

[seanc]

Can I strip the zinc off new commercial fasteners by just using muratic acid?

Yes.

Mix it 15-25% w/water. Full strength will strip the zinc fast, but will also etch the raw steel. The weaker solution takes about 5-10 minutes to strip the zinc, but doesn't hurt the steel. The zinc fizzes as it dissolves. Pull the parts out when the fizzing stops.

Is "copycad" a good surface? or does it have to be zinc?

CopyCad is zinc.

Sean

[drdelano]

Is "copycad" a good surface? or does it have to be zinc?


CopyCad is zinc.

I knew that... I was just testing you