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Is passivate enough for stainless shot peening?

2005

I am the manufacturer of stainless steel furniture,grade 304 .

Our products use stainless shot peening to do the surface finish,it's look perfectly nice.
But the problem is after the products have been exposed to the environment for 6 months (Normal,outdoor environment)..It appear to have rust on it..on the surface (tea stain or pitting ,I'm not sure what it's called)..But nothing on the welding area..All the welding area are pickled with commercial pickling gel..and we clean it before go to the peening chamber..

After the chair has been shot peened.We clean them with distilled water ,alkaline cleaning..I have followed the ASTM A967 for the passivation process ..All the process is carefully managed...

so I was wondering..Is the passivation with nitric enough?..Do I need to do the Pickling with the commercial pickling gel for the whole chair or table ..Or should I use the pickling bath instead of doing the passivation?

Need help,

Kelly J.
Stainless Furniture - Thailand

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I assume that the weld material is purchased locally, and with pickling it and passivating it you should get good results. Passivation correctly with nitric acid according to ASTM A967 should give you good results unless it is exposed to salt spray or other chloride environment in the field. Pickling the entire unit is not likely to help you.

I assume that you are using clean, non-ferrous media for grit blasting, and you change it fairly often.

There is a lot of questionable grade 304ss available on the market these days due to the shortage. This does not mean your supplier is intentionally giving you bad steel, just giving you what is available from the sources. If you want to talk about other things you can try give us a call.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2005

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2005

Really appreciate your response.

Yes, we were using the new Stainless steel shot (round ball not grit)..

It's just confuse me whether after shot peened what process do we really need..Pickling or Passivation..

Kell J.
- Thailand

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Normally, the reason that you blast the surface is to clean off any scale, so you should only need to passivate after the peening.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2005