Passivation VS Pickle
Passivation VS Pickle
(OP)
I am passivating 316ss with 50%nitric and 50%water for 30 minutes at 72 degrees f and passing a copper sulftate just fine. But recently I saw a print that said pickel. Can & how do I pickle with nitric & water. My Question is what is the differance between Passivation & Pickle.





RE: Passivation VS Pickle
Michael McGuire
http://stainlesssteelforengineers.blogspot.com/
RE: Passivation VS Pickle
Passivation is an oxidizing environment that will only remove easily soluble metals like Fe, and only at the surface. It will also promote formation of a more solid Cr oxide layer.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: Passivation VS Pickle
Whoever specified pickling had some reason for doing so -- most commonly, to remove heat treatment scale or welding scale & heat tint. See ASTM A380 Standard Practice for Cleaning, Descaling, and Passivation of Stainless Steel Parts, Equipment, and Systems for pickling solutions & instructions: http:/
Passivation in the USA is mostly specified per QQ-P-35C (old, but still common) or ASTM A967 or proprietary spec. Some use ASTM A380 although technically it's a guideline, not a spec. QQ-P-35C is a free download: http:
A useful article "HOW TO PASSIVATE STAINLESS STEEL PARTS" from Carpenter Technology: http://
RE: Passivation VS Pickle
In some high purity services passivation is critical. On a microscopic level you are forming a sruface layer that is very Cr rich. Instead of the standard Cr:Fe ratio of 0.25 on the bulk alloy, a well cleaned and passivated surface will have a ratio of 2 or higher. You will selectivly disolve Fe from the surface. You also form a chrome oxide layer that is denser, thicker and more chemically stable.
= = = = = = = = = = = = = = = = = = = =
Rust never sleeps
Neither should your protection
http://www.trent-tube.com/contact/Tech_Assist.cfm