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Stripping Chrome Plating From Stainless Steel Substrate
Q. I need some assistance in the removal of chromium deposition from a stainless steel PVD part. I'm a project manager for a semiconductor equipment refurbisher, in charge of trying to clean AMAT PVD parts to OEM specs.
Normally, one would use HCl to remove the chrome, but since the substrate is stainless steel, I need another chemistry make-up that will not damage the stainless. I remembered using potassium permanganate [on
eBay or
Amazon] in the past, but I don't remember what other chemistries were used along with it.
Can anyone help me on this?
- Dallas, Texas
2006
2007
A. Dear Mr. Malcolm K. Brown
Yes exactly, you are correct. The chemistry which is used to strip the CrN or chromium is as follows:
Take step 1) 1 lit of DI water heat up to 50 °C.
Then take step 2) 15 gms of KMnO4 and 40 gms of KOH
mix step 2) in step 1) then insert the tools which has to be stripped
Heat the solution up to 90 ° C.
Here your stripping time will take 4-5 hrs.
We can reduce the stripping time by varying the composition of KMnO4 and KOH.
All the best. If you have any doubt please reply so that I can answer .
Regards,
Murali
A.Murali Krishna
pvd process engineer
Pune, India
Q. DEAR MURALI
It was very interesting to read your ready solution to stripping chrome given to Mr Malcolm K Brown.
My question is whether it works only on stainless steel substrates (preventing substrate attack) or also works on bronze, brass, etc.
I have used hot sodium hydroxide 20 % aqueous solution and elemental flowers of sulfur
[affil links] sprinkled on top, to remove copper plating from hi-tensile components without hydrogen embrittlement or substrate attack.
Regards,
- DUBAI, UAE
2007
A. Dear Mr.Vinod,
I am not getting your point clearly. Please explain to me in brief so that I can help you if you have time.
Regards,
A.Murali Krishna
pvd process engineer
Pune, India
2007
Q. We have a part that is chromed and the original material is AISI 420. Will stripping the chrome damage the 420? If it will, what is the process strip and re-chrome without damage?
Rob Mercer- Topeka, Kansas, USA
August 6, 2013
A. Two choices-
20 - 25% hydrochloric acid or
caustic soda
[affil links]
solution with reverse current.
Both methods have to be watched closely or the part can pit.
James Watts- Navarre, Florida
First of three simultaneous responses -- August 8, 2013
A. Rob, it depends on a lot of factors such as whether or not there is nickel under the chrome. I don't recommend using acid in any case. Popular options include an alkaline solution and then buffing/polishing or blasting without the alkaline process followed by buffing/polishing. Yes, damage can be caused, that is one reason the buffing/polishing is usually required but the damage can be minimal in many cases, depending on the client's requirements and particular application.
Blake Kneedler
Feather Hollow Eng. - Stockton, California
Second of three simultaneous responses -- August 8, 2013
A. Hi Rob,
A common way to remove chrome plating is to use a 10% sodium hydroxide (caustic soda
[affil links]
) solution, applying an anodic voltage of about 3-6 volts. This should not damage the base material as long as the solution is maintained and you don't allow cross-contamination.
If the parts are highly stressed or need fatigue resistance then I would recommend that you get the parts control shot peened to increase the compressive stress in the base material before re-plating (chrome plating can reduce fatigue strength quite considerably).
Aerospace - Yeovil, Somerset, UK
Third of three simultaneous responses -- August 9, 2013
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