SYMPOSIA PAPER Published: 01 January 1937
STP41377S

Passivation Treatments for Resulfurized, Free Machining Stainless Steels

Source

The practical aspects of nitric acid passivation are reviewed and new data on the effect of passivation variables on subsequent corrosion resistance are reported. Solution composition and temperature, passivation time, and double acid and alkaline treatments were investigated. Commercial heats of 12Cr (0.5 and 2 percent varieties) and 18Cr-9Ni resulfurized stainless were tested at 95°F (35°C) in either 95 percent humidity or 5 percent salt spray after receiving the various passivation treatments. The variables having the most significant effect were (1) the manganese content of the steel, (2) whether a cross or a long section of a bar was being investigated, and (3) an alkaline post passivation treatment. Without passivation, the low manganese 12Cr alloy has superior corrosion resistance to the high manganese grade. After passivation, the low manganese alloys lost some of their corrosion resistance, whereas the high manganese materials sometimes showed improved resistance. The loss of resistance after passivation is attributed to the retention of acid in partially removed sulfides and it can be minimized with the alkaline treatment. It is also noted that highly oxidizing passivation solutions are required to avoid attack during the passivation treatment itself and that these solutions do not dissolve tool steels, particles of which might be embedded in the stainless surface during machining.

Author Information

Henthorne, Michael
Carpenter Technology Corp., R & D Center, Reading, Pa.
Yinger, R., J.
Carpenter Technology Corp., R & D Center, Reading, Pa.
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Developed by Committee: A01
Pages: 90–105
DOI: 10.1520/STP41377S
ISBN-EB: 978-0-8031-6044-6
ISBN-13: 978-0-8031-6198-6