This study examines the effect of alloying elements of Ni and W on the repassivation properties of stainless steel (SS) as evaluated by a rapid scratching electrode technique and stress corrosion cracking (SCC) test. The SS specimens were grouped into two different grades according to Ni content (22Cr-5Ni duplex, Type 317LMN [UNS S31726] austenitic SS). Major considerations regarding alloy design were Ni content and the substitution of W for Mo. However, a similar pitting resistance equivalent number (PREN) of 35 to 36 was maintained for all specimens. The main factors for evaluation of repassivation properties are the peak current for the scratched surface and repassivation rate. In 1 M magnesium chloride (MgCl2) and 1 N sulfuric acid containing chloride ions (H2SO4 + 3.5% Cl−) solution, repassivation test results showed that repassivation properties decreased as Ni content increased. However, W substitution was effective on the repassivation process and increased the resistance of SCC property for alloys containing high Ni content.

Subject
Nickel based alloys, Molybdenum alloys, Passive films, Repassivation, Chloride solutions, X-ray spectroscopy, Sodium chloride solution, Pitting, Passivation, Alloys, Stress corrosion cracking, Potentiodynamic polarization, Chloride stress corrosion cracking
Keywords:
austenitic stainless steels, duplex stainless steels, passivation, polarization, repassivation, scratching electrode technique, stress corrosion cracking
NACE International
2005
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