Citric passivation.
Draw, clean, rinse*, passivate, vacuum anneal, restrike for final part shape, clean, rinse, citric passivate, vacuum anneal. Double the chances for pitting!
*it wasn't clear to me how or if they dried the parts, I suspect they clean-rinse-dunk directly into the citric in...
even worse...no agitation during the alkaline cleaning prior to passivation. (extra large sigh)
Pitting only occurs sporadically, so 99% of the time the process has been fine--slapdash, but fine.
They are going to switch to non-chlorinated products and DI water.
Also by the way, I've been a...
I knew I posted too soon...
-lubricant is a chlorinated parafin (sigh)
-rinse is city water
I wanted to be prepared to suggest all the places to look, but I didn't have to look hard.
Ultimately, I suspect it is a poor rinsing issue.
Helping out on a problem in a 304L part that sporadically has pitting after deep draw process.
I honestly don't know all the details yet of the exact processing steps other than what I can glean from the failed part:
-Deep draw in at least 2 steps (there are remnants of a shockline on in the ID...
