Descaling 17-4 Stainless Steel
Descaling 17-4 Stainless Steel
(OP)
During the precipitation headening process of 17-4 PH stainless steel a light heat tint (oxide film) on the surface is created. Normally, we require the heat tint to be removed either by mechanical means such as wet grit blasting, or by chemical means such as light pickling for several minutes in 10% nitric 2% hydrofluoric acid *by volume) solution at 110-140 F. However, I have been told that precipitation hardening in a vacuum eliminates the heat tint (oxide film) created during the hardening process.





RE: Descaling 17-4 Stainless Steel
RE: Descaling 17-4 Stainless Steel
RE: Descaling 17-4 Stainless Steel
RE: Descaling 17-4 Stainless Steel
RE: Descaling 17-4 Stainless Steel
Stainless is bright annealed in a hydrogen/nitrogen atmospere with an very low dew point, but even so it is rinsed in nitric afterwards to remove the minor scale.
Be cautious with only mechanical scale removal. There is a dechromized layer on the surface caused by the oxidation and you need acid to remove it. It may be possible to seem to get a good descaling only to end up with bad corrosion resistance in the field.
RE: Descaling 17-4 Stainless Steel
RE: Descaling 17-4 Stainless Steel
Mcguire is right about the dechromized layer. Check out "Heat Tints on Stainless Steels can Cause Corrosion Problems" by Tuthill & Avery, Nickel Development Institute Reprint No. 14050, at www.nidi.org.