replicating cad and zinc finishes

[Todd H 26112]

Re: replicating cad and zinc finishes

Was the usage of beed blasting mentioned for cadmium or is that also what you use to strip chrome and prep before taking it into the plater?

thanks,

[Terry M.]

Bead blasting chrome *TL*

I once had to remove some chrome in order to paint bumpers. I tried blasting all kinds of media at them, and found nothing that would cut it. I ultimately paid a plater to reverse the plating process to remove the chrome.

[Jack H.]

Re: Bead blasting chrome

Some platters (the good guys) WILL dechrome by reverse polarity bath, but most won't. Few do flash/smack chrome with virtually all doing triple chrome or 'show' chrome work (steel, copper, nickle, then chrome). They claim reversing polarity on a part to remove existing chrome 'mucks up' the chemical purity of their final chrome bath, so they prep parts exclusively by etching in hot acid bath to get down to raw steel/pot metal.

Of course, by etching the part, you can't control uniformity and you'll get pit + surface irregularities that have to be manually buffed before the re-plate process can begin (no true for reverse polarity dechroming).

The 'good guys' here who will dechrome by reverse polarity, do the job by setting your part aside and waiting for their chrome tank to be virtually depleted and in need of fresh chemistry. THEN, they'll make their run of reverse polarity dechrome jobs because the main bath is essentially 'spent' anyway. So, it's a rare plating shop that will dechrome by reverse polarity while you wait (the job can actually go that fast)....

[Tracy C.]

Re: replicating cad and zinc finishes

Todd,

First ask your shop if they will work with you on this. If so, see if they will strip the chrome with reverse polarity. If not, the Caswell plating manual tells how to do this at home with a car battery and supplies they sell.

After stripping, take a DA sander and sand the remaining nickel plate off and then wet sand progressivly from 220 to 400 grit wet or dry paper using a firm foam sanding block. Be sure to tap out any dings or dents prior to sanding.

Next, Buff the dog out of it with some black emery compound and a wheel buff mounted on a buffing motor (bench grinder type and DON'T forget your leather gloves)

If you still have pits, ask your plater to put a heavy copper plate on it and then take it back home for more progressive wet sanding. Think of the copper in the role of "bondo" during this phase. (filling pits and deep scratches)

Buff again and take it back for another copper plate. Hopefully when you get it back all that is required is a finish buff before the nickel and chrome.

This is kinda pricey and very time consuming, but if original parts matter to you, it's the only way to restore your air cleaner lid.

good luck,
tc

[Todd H 26112]

Re: replicating cad and zinc finishes

Thanks - makes perfect sense, (multiple) heavy copper applications between buffs to a uniform surface to at last chrome. Just the info I was after.

I also didn't realize that Caswell offered some supplies for deplating as well but it makes sense they would.

thanks,