Post-working passivated 300 series SS...

[quizzical1]

Hi All,

We have 303 and 316SS parts that need to be assembled after passivation - one being a crimping operation. Is there any assembly guidelines we can follow so as not to damage the passivated surfaces - especially for the crimping operation?

TIA

~Q

 

[TugboatEng]

What is the crimping tool made from?

Passivation for stainless steel is a simple process. It shouldn't be too much of a burden to passivate again. There are pickling pastes that can be used to touch up contaminated areas.

 

[EdStainless]

First, is it a problem?
Have you tested pieces to see if you get any rust spotting?


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P.E. Metallurgy, consulting work welcomed

 

[quizzical1]

thanks guys - as usual I need your help again....

Crimping tool - hardened O-1
can you please steer me to testing substances? are we talking Copper Sulphate? never heard of pickling pastes...

 

[EdStainless]

The easiest test would be one of the following:
1. Use white Head and Shoulders shampoo. Put a light coat on the part and then gently mist with pure water to keep the surface damp (but don't alloy drips). You should be looking for blue spots. It may take an hour or two.
2. Find a warm location (85-100F) and lay down a clean towel that is dampened with pure water. Set parts on it and cover with another damp towel. Let stand overnight.
Yes, it is a simplified humidity chamber. In the morning check for orange spots. I have done this with disposable diapers instead of towels.

For pure water purchased distilled is good enough.

I preferred D-2. It is high enough in Cr that it rarely causes issues.

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P.E. Metallurgy, consulting work welcomed

 

[quizzical1]

Wow, mind blown….

Never would have thought of this!!

Same for EP parts?

 

[EdStainless]

These methods can be applied to any SS parts.
The reason that some H&S is white, and some blue is the same reason that Selsun Blue is blue.
The active Se in the formulations will complex (it doesn't bond) with Fe and have a blue color.
If your plant is 100% SS then you can keep it white.
You do have to wash parts very well after this because H&S also contains chlorides, the use salt to adjust the viscosity.
They do this with all liquid soaps, some dish soaps are 4% salt.
I have done this in the inside of large vessels.

We used to have a neighboring plant that made the material for disposable diapers.
It was in 36" wide sheets on rolls. We would buy scraps and trims from them.
It was another way to create a high humidity environment.

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P.E. Metallurgy, consulting work welcomed

 

[quizzical1]

Thanks, Ed!!