[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.