Reverse electrolosis/acid de-plating

[johnshenry]

I tried this this past weekend with some info from a fellow enthusiast who had been sucessful at it. The subjects are pot metal car parts (small) that are triple chrome plated. I want to strip the exisiting plate, fill, prime and copy chrome.

I mixed a solution of battery acid and tried a coupel \"junk\"handles. I got good results at first, then tried an earlier better handle and it didn\'t work well at all. one area \"over stripped\", ate well into the pot metal, while the other end didn\'t de-plate at all.

I sense that this might be a delicate procedure, especially on acid sensative pot metal, but wondered if anyone else had been successful at it. In particual:

What kind of acid solution did you use? I bought sufuric acid from an auto parts store in a white, rectangular plastic container. I mixed it with tap water about 25/75% acid/water. Dont know what the \"out of the bottle\" concentration of the acid was, couldn\'t interpret the numbering on the label (anyone know?).

What kind of cathode (or would it be anode) do you use? I used a high carbon M10 bolt. The deposits that formed on it were red-copper color and wiped right off.

What kind of current did you use? I have a very large volt and amperage controlled DC supply and had to crank 8-12 amps through to get the stuff to deplate, and it still took 20-40 mins. Is this normal? Solution got pretty warm.

I have sand a bead blasting capability, is that generally considered a better solution for de-plating small, intricate parts?

Thanks for any insight.

John H.

[48Buick]

John:
I dont use any acids with potmetal. It just creates problems down the road. You really want to mechanically remove the chrome.
Try sandblasting the chrome off and sand smooth. Drill out any pits. Then you will have a nice nickel surface to start plating on and building up from there.
What are you using for a strike plate on the potmetal?
Potmetal is a real pain in the neck sometimes.
48 Buick

[johnshenry]

How will I have a nickel surface after media blasting?

I was planning on using the electroless pot metal primer, then copy chrome.

JH

[48Buick]

John:
The nickel is the underlying plating under the chrome.
When potmetal parts are chrome plated they are usualy plated in this manner.
First a strike plate to protect the potmetal from the next bath.
Then the nickel and then the chrome.
If you strip off the chrome with sandblasting, you will have gotten to the nickel. If you have pits and such in the part you will have to prime it and then go into the copper bath for some filling with the copper, then nickel and then the copy chrome.
What were you planning on filling the pits with?
48Buick

[mcaswell]

48Buick wrote:
John:
I dont use any acids with potmetal. Potmetal is a real pain in the neck sometimes.
48 Buick

Good advise...you really have to be careful with using acids and Pot Metal. As you saw, it\'s very easy to have your part dissolve away into nothing.

[johnshenry]

\"If you strip off the chrome with sandblasting, you will have gotten to the nickel\"

Wouldn\'t I have gotten to the pot metal?

I was planning on filling the pits with Solder-It, but I have had ZERO succes with this stuff and am very frustrated. I can\'t get it to \"take\" to any pot metal parts; parts that contain zinc as they \"fizz\" with the application of acid.

I plan on stripping, pot metal priming, then copy chrome plating.... but haven\'t had much luck so far.

[48Buick]

John:
When the potmetal was initially plated, this was most likely the process.
cyanide as a strike plate
nickel plate
chrome plate.

So.........if you strip off the chrome you will see that you go to the nickle plating.
In some areas you may likely go down to the potmetal.
Either way you will want some type of a initial strike to put on the potmetal so you dont eat it up in the acid copper bath.
Im not familiar with the potmetal primer but it sounds like a electroless nickel to me.
I personaly use a cyanide copper strike and have also used a High sulfate nickel bath on the potmetal.
You will have to protect that potmetal with some kind of a strike though.
Then you can plate with copper and fill your pits with solder.
After sanding and smoothing, go to your nickel and then the chrome.
Hope this helps
48Buick

[mcaswell]

We\'re realeasing a new product called \"Flash Copper\" in the next few days.

This new product does an AMAZING job of plating copper onto pot metal, lead and other metals and will help many people having problems plating pot metal.

It\'s as effective, if not more so, as a cyanide copper system, without the dangerous cyanide.

Watch this space for the link to the product.