Étude de la susceptibilité à la corrosion d’aciers inoxydables AISI 304 ET AISI 316 soumis à des contraintes mécaniques dans l’acide nitrique dilué bouillant en présence de chlorures

¹ Laboratoire de Mécanique Physique, Unité de Recherche Associée au CNRS n° 867, Talence
² ENSCPB, Talence
³ EdF, Groupe des Laboratoires, Saint-Denis

Abstract

A detailed study of corrosion of stressed 304 and 316 stainless steels in boiling solutions of diluted nitric acid in presence of chloride is presented. After a chemical study of the electrolyte, the different kinds of corrosion observed are represented on HNO₃ concentration — Cl^– concentration diagrams.

A more fundamental study based on several electrochemical techniques (forward scan and return potentiodynamic curves, potentiokinetic curves with different scan rates, sample depassivation by rapid straining under potentiostatic control) is carried out. The results allow to confirm the observations and to explain them in terms of competition between anodic dissolution, depassivation, repassivation processes with a precise analyze of the role of the solution and of the mechanical stress.