Stripping Plating from Random Parts

[CaddmannQ]

I’ve only used one electrolyte before (sodium carbonate) and it may not be the best for what I want to do.

I have some experience running a reverse electrolysis tank, in order to strip the rust off of steel parts, but I have seldom attempted to strip the plating off of cadmium plated or zinc plated parts. As I recall, it took forever.

Mostly I’m going to be stripping some fasteners and small steel brackets that might have cadmium, reverse cadmium or zinc. (Someday I may try to strip some chrome parts but not for now.)

I have one of these blue plastic orange juice drums that holds about 55 gallons, with the top cut off, and an old battery charger.

I know that this will work, but I don’t have a clue about the best electrolyte to use in this case. I am normally just using Arm and Hammer washing soda. About one cup in 50 gallons of water seems to work fine.

When I read through the article in the tech section here about electrolysis, there’s one thing that I didn’t see mentioned. This is a very line-of-sight process, between the rust and the sacrificial steel anodes.

I had my best and fastest results when I did two things. One was to surround the object being stripped 360° with sacrificial anodes.

The second thing was to use thin anodes with lots of edges and surface area. A screen will work but it doesn’t last very long. What I found worked well was laminations from old electric motors or transformers. They are thin and have lots of edges.

Also I’m wondering if the sludge that comes out of the bottom of tank becomes really toxic when you are stripping cadmium or zinc?.

When stripping rust, all I get in the bottom of the tank is rusty mud.

[Ironman]

Use muriatic acid to strip the plating off.
Hydrochloric acid is used as pool cleaner. It will also strip off zinc

[Shade Tree Welder]

Ok, Why do you think you need to strip the fasteners? I would suggested
buying new fasteners that are not plated.

You are not going to like my answers.

Cadmium, Do not even try to strip it, you are likely going to poison yourself or
someone else. Cadmium is high toxic and Cad plating is actually a conversion
coating that contains chromium, and in any stripping process you will create
hexavalent chrome. So you have a place to dispose of this high toxic waste
you will create. Hell in california they will likely send you to jail if you do it.
Just don't it is a very very bad idea...

Zinc, okay you are not going to kill yourself or anyone else and zinc is easy to
remove. But I would not use an acid, acid strip will set up your fasteners for
stress corrosion cracking, hydrochloric (muratic) acid being the absolute
worst for this. Sorry Gerry very bad recommendation. Phosphoric acid would
be the least damaging to the steel underneath. 85% Phos acid will do a great
job. However a much better solution, pun intended, get some lye, like drain
cleaner, and soak your parts in that, it will remove the zinc just as effectively
and not set the steel up for corrosion. Rinse the parts well in hot water and
you are good to go.

Here is a good source of pure sodium hydroxide (lye). You will want to mix it
with water in equal parts by weight with water. That bottle is 2 lbs lye, a
quart of water is ~2 pound, so 1 quart water with the whole bottle of lye.

https://www.farmandfleet.com/product...in-opener.html

[Ironman]

Good points, Ron.
I often strip rust from small objects with HCL, and I never knew or experienced stress corrosion cracking.
Largest one was eating the rust out of a 4 gallon diesel fuel tank. I'm sure you are right, but I may have been lucky.

[Shade Tree Welder]

Originally Posted by Ironman

Good points, Ron.
I often strip rust from small objects with HCL, and I never knew or experienced stress corrosion cracking.
Largest one was eating the rust out of a 4 gallon diesel fuel tank. I'm sure you are right, but I may have been lucky.

Sulfates and chloride ions are hell on steel, look at what chloride does to cars
on salty winter roads. Phosphates are much more mild. Also you can leave
iron phosphate behind on a steel or iron surface that will aid a little with
corrosion protection.

[CaddmannQ]

These are old antique parts and you can't buy 'em.

I don't know what they are plated with anyhow. I want them painted and I didn't want to etch them too much. Otherwise I do have some phosphoric acid wash that will strip stuff. I always use that before painting steel.

I have one kind with detergent action and one with alcohol.

Some parts were advertised as "bright dipped" whatever that means.

I imagine there are lots of different plating formulations used since 1900.

[CaddmannQ]

Originally Posted by Shade Tree Welder

. . . You are not going to like my answers.
. . .

You may be assuming too much.

I come here FOR the answers.

If I want my ego buttered I'll go elsewhere.

[Shade Tree Welder]

Originally Posted by CaddmannQ

You may be assuming too much.

I come here FOR the answers.

If I want my ego buttered I'll go elsewhere.

LMAO!!! Yeah we only smash egos here.

So you are painting them, I would go with the detergent phos acid wash. Even
after washing and rinsing it will leave a mildly acid surface and the promotes
paint adhesion.

There are a number of retail solutions that use either iron phosphate or zinc
phosphate surface conversion coatings that aid in painting on top of, some
are even dry in place coatings. Follow the label in use.