The Effect of Test Method and Surface Condition on Pitting Potential of Single and Duplex Phase 304L Stainless Steel

Pitting potential measurements have been made by potentiostatic, potentiokinetic, and scratch test methods. Several surface conditions were tested to determine the relationship between test methods, surface condition, and experimental procedure on both base and weld metal. The results indicate the complex interrelationships between specimen mounting technique, exposed edge effects, test methods, and surface condition on pitting potential determination. It was found that base metal pitting potentials are a strong function of the above mentioned effects, while the duplex weld metal is independent of them. This is explained by the nature of the pit initiation sites which are the sulfide inclusions in the case of the base metal, and the austenite-residual delta ferrite in the weld metal case.