Electrochemical methods for the determination of Pedeferri's diagram of stainless steel in chloride containing environment

Abstract

Stainless steels are prone to localized corrosion (pitting and crevice) in the presence of oxygen and chlorides over a critical threshold. Prediction of the corrosion behavior of stainless steels in chloride containing environment is of great importance; for this reason, Pedeferri's diagram is proposed to define corrosion and passivity (perfect and imperfect conditions) as a function of the potential and chloride content. In this paper, the first effort is carried out to define electrochemical conditions to obtain the diagram. Potentiodynamic and potentiostatic polarization tests are performed on AISI 304L type stainless steel. Localized corrosion potential and critical chloride content found with two different methods are in fair agreement. Pedeferri's diagram is built for type 304L stainless steel at room temperature and pH 6. Corrosion, perfect and imperfect passivity regions are separated by scattering band for localized corrosion and repassivation potentials.