Plating over zinc dichromate

[pnoeth]

I purchased several spring clips that hold the heater box together on a project car. They are brand new and plated in zinc dichromate (yellow zinc). From what I can tell from photos, the original clips on the car ('65 MG Midget) when new were silver in color and most likely plated with zinc chromate (sliver zinc) or cadmium (silver cad).

I would like to plate the clips so they are silver in color. Do I have to remove the zinc dichromate first or can I plate over it with Copy Cad or Zinc plating? If I need to remove the zinc dichromate first, how do I do that?

Thanks for the help!

[KCV6]

You will need to strip the gold chromate first. If you are thinking of getting a copy cad system, then your best bet is to strip the springs back to bare spring steel and re-plate them.

Cheers... Mark

[pnoeth]

Any advice on the best way to strip the existing plating off the clips?

Thanks,
Paul

[woodjames]

Quick dip in battery acid should do the trick. Just go until it stops fizzing.

Any advice on the best way to strip the existing plating off the clips?

Thanks,
Paul

[pnoeth]

I just tried something that worked out well. I read that the yellow-green-blue rainbow color on the zinc dichromate is an oxidization that actually protects the zinc, giving the part better corrosion protection than plain zinc chromate.

I wondered if I could remove the oxidized layer and leave a silver coating. I used automotive rubbing compound and the dichromate color came off with surprising ease. It took two or three minutes of rubbing and the clip is sliver and shines very nicely. Problem solved.

I think I will give them a quick spray of clear lacquer before installing just so they stay nice looking a little longer.

Paul

[jkeating7]

24 hours in distilled white vinegar will remove all the old plating. Although you don't want to used it on any metal that flexes easily.

[XK120DHC]

I used automotive rubbing compound and the dichromate color came off with surprising ease. It took two or three minutes of rubbing and the clip is sliver and shines very nicely. Problem solved.
Paul

Paul;
I think I will disagree with your "Problem Solved" and say you discovered a "problem" with your new clips.. If the "Yellow Cad look" rubbed off with rubbing compound, the chromate was (Is!) totally ineffective!
A Zinc Plated part that has been "sealed" with a quality Chromate should withstand being submerged in an acid strip for a minute or so. Chances are, your "yellow dichromate" is really just a "yellow wash" to make it "look like" it was properly chromated. (the chromate is there to protect the zinc from corroding prematurely). I'd also question if the clips were even zinc plated to begin with..
In all the years (decades) I restored cars (professionally), I often ran into inferior quality parts like you have discovered.. and from the better quality vendors! I guess that was the beginnings of the "Asian Invasion"..
Additionaly, as an FYI, if you plan to re-zinc plate any "store bought" parts, strip them to bare metal and start from scratch.
Attempting to strip off the chromate is fruitless.. either "some" chromate is left behing or the base zinc is eaten off to bare metal.. both will result in a crappy replate/rechromate job.
Hope this helps.