ACID ETCHING 300 Series Stainless Steel

[Elephantine49er]

I have performed Nital/Ammonium Persulfate acid etching on Carbon Steels to verify removal of Arc Burns per ASME B31.4 and B31.8, but have never applied this technique to Stainless. Are these solutions detrimental to Austenitic Stainless such as 304 and 316L or would this be an appropriate technique?

Any help would be great.

Thanks!

David.Blosser@kinetic-solutions-llc.com

http://www.kinetic-solutions-llc.com

 

[Duwe6]

Best [and scariest] cleaning & passivation solution for s/s is 10% nitric and 5% hydrofluoric. Works fast at room temp, fully passive in just a few minutes.

 

[MJCronin]

Why use any type of acid to remove arc strikes ?

In my experience, when these were removed, it was always by careful grinding and perhaps polishing.

The benefit here, as I understand, is to remove the "stress raiser" caused by the strike by smoothing the surface.

Careful grinding can do this, acid removal of arc strikes..... does not.

MJCronin
Sr. Process Engineer

 

[Elephantine49er]

Thanks, Duwe6. I'll look into that solution.

MJCronin: The acid is only used to verify removal of the arc strike. Still accomplished by grinding.

 

[EdStainless]

Nitric/HF will attack any area with sensitization, but there are many forms of microstucture damage that don't pickle differently (and we use 20% Nitric, 5% HF).
What kind of damage are you looking for?
There is no phase change. So either sensitization or contamination are the only things that I can think of.
Just about any good macro-etch will work.
But since this is stainless never use any HCl.

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