passivation of PH13-8MO 1

[dho]

should passivation be done over the whole part prior to shot peen (mil-s-13165) which covers part of it ?
thanks.

 

[EdStainless]

I don't see a reason to since you will have to passivate after shot peen.
I believe that AMS 2700 is the passivation spec for stainless steels.

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P.E. Metallurgy, Plymouth Tube

 

[dho]

like Sikorsky, says passivation after machining. if shot peen is not MACHINING, so the passivation should be done PRIOR to it.
comments?
thanks.

 

[EdStainless]

So you shot peen process is so clean that you can still pass a free iron test afterwards?
It is a surface modification, I would passivate afterwards.
Ignore this at your own risk, I wouldn't want my customer to complain about rusty parts.

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P.E. Metallurgy, Plymouth Tube

 

[WKTaylor]

Passivation is always one-of the last steps... heat treat, clean, grind/machine, NDI, shot-peen, passivate, prime/paint/coat/etc [IF specified]. .

Shot-peening passivated surfaces will wipe-out the effects of the passivation for multiple reasons [causes].

Also, AMS2700 includes method 2 passivation, using citric acid. Unless not allowed for a specific alloy, this is a 'green' preferable process... other acids are downright dangerous and difficult to contain.

Regards, Wil Taylor

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[dho]

the shot peen surface is always plated/coated. does that make issue of passivation prior or after a moot point (if we forget the completeness of the coverage)?
thanks.

 

[EdStainless]

Maybe in your world, but peened surfaces are not always coated.
You still need to clean after peen before surface coating.

Ctiric acid isn't my favorite, it must be warm and it takes a while.
A short dip in room temp Nitirc is easy, fast, and reliable.

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P.E. Metallurgy, Plymouth Tube

 

[mcguire]

Passivate AFTER! Disrupting the surface by blasting is similar to sanding. It decreases corrosion resistance gained from acid pickling. Follow EdStainless recommendations.

Michael McGuire

 

[mcguire]

EdStainless

Can I reach you via Plymouth Tube?

Mike McGuire

Michael McGuire

 

[EdStainless]

yes Mark, eblessmanatplymouthdotcom

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P.E. Metallurgy, Plymouth Tube