The Kinetics of Anodic Dissolution and Repassivation on Stainless Steel 304L in Solutions Containing Nitrate

In this paper we investigate the influence of nitrate ( ) on the dissolution and repassivation kinetics of freshly bared stainless steel 304L surfaces generated during scratch tests. To differentiate anodic dissolution from film formation during early decay times, t < 20 ms, we have developed a mathematical expression for fitting this portion of the transient. The expression assumes the total current owes to dissolution plus film formation where the oxide coverage is derived from Avrami growth kinetics. In this manner the approach allows the investigator to separate the film formation and dissolution currents from the decay transient and analyze them individually. It is shown that film formation in 0.9 M occurs more rapidly as compared to 0.1 M chloride (Cl − ). In addition, was characterized by thinner films (< 0.6 nm) and higher electric field strengths (1.1 × 10 7 V/cm) at early times. Correspondingly, increasing Cl − concentration from 0.1 to 0.9 M resulted in thicker passive films (0.6–2.2 nm) and lower electric field strengths (3.7 × 10 6 V/cm).