apurdey

Re: Cleaning and passivating stainless steel

What is the easiest and best way to clean stainless steel after removing the welding heat marks with hand-held passivation equipment? We are seeing cloudy "stains" that can be removed mechanically, but we prefer a chemcial treatment instead.

bill doherty

Re: Cleaning and passivating stainless steel

Hi,
I have a bit of experience here.
Please advise stainless grade and end finish required.
Regards,
Bill Doherty

apurdey

Re: Cleaning and passivating stainless steel

Thanks for the invitation.

The alloy is 304, with #4 finish. The product is a welded Nema type 3 enclosure. The cleaning being done is to remove the heat marks from the welded areas. The product has been rejected at times due to what I would call water marks or stains.

Regards,

Al

bill doherty

Re: Cleaning and passivating stainless steel

Hi Al,
Just a few words of caution:
304 is subject to "tea staining" if subject to corrosive elements.
Might be a good idea to observe the entire weld prep/process and cleanup.
This might avert your problem altogether.
Chemical cleaning and passivating can use some pretty nasty chemicals.
If you are not well trained in chemistry get some one who is to experiment.
That said I would suggest a 5 percent 1 n hydrofluoric acid / 5 percent 1 n nitric acid solution as an immersion cleaner/passivation solution.
Try some prepared test pieces first.
It is easy to up concentration / temperature later to achieve desired speed.
Make sure test pieces are thoroughly rinsed.
Make sure spent solutions are disposed of appropriately.
Hope this helps,
Regards,
Bill Doherty

Ray Kremer

Re: Cleaning and passivating stainless steel

apurdey;1039 wrote:

What is the easiest and best way to clean stainless steel after removing the welding heat marks with hand-held passivation equipment? We are seeing cloudy "stains" that can be removed mechanically, but we prefer a chemcial treatment instead.

This sounds like you are removing the weld discoloration using an electrochemical process, which like any other effective method for removing the discoloration can affect the surface finish of the metal, leaving formerly polished areas with a more matte finish, which is what I assume you mean by "cloudy".

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