SYMPOSIA PAPER Published: 01 January 1972

Relative Critical Potentials for Pitting Corrosion of Some Stainless Steels


The breakthrough potentials of stainless steel alloy Types 409, 304, and HWT were determined in solutions containing various concentrations of chloride ion, ranging from 10 to 40,000 ppm. Four different salts were used to introduce the chloride ion: sodium chloride, calcium chloride, cupric chloride, and ferric chloride. The breakthrough potential values obtained decreased with increasing chloride ion concentration. These breakthrough potential values were plotted against the logarithm of the chloride ion concentration and a straight line drawn through the lowest potential points for each alloy. This line described the minimum pitting potentials for each alloy and was used to compare the three alloys studied. Using this method, HWT proved to be a more pit resistant alloy than Type 304 which in turn was more pit resistant than Type 409.

Author Information

Johnson, MJ
Allegheny Ludlum Industries, Inc., Research Center, Brackenridge, Pa.
Price: $25.00
Contact Sales
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Developed by Committee: G01
Pages: 262–272
DOI: 10.1520/STP35425S
ISBN-EB: 978-0-8031-4617-4
ISBN-13: 978-0-8031-0110-4