Long-term behaviour of AISI 304L passive layer in chloride containing medium

In this research, the behaviour and evolution of passive films generated on AISI 304L are studied for a long immersion time in chloride containing media. A combination of electrochemical (cyclic voltammetry and electrochemical impedance spectroscopy) and surface analysis techniques (AFM and XPS) is used in this work in order to analyse the changes that chlorides induce in those films as immersion time increases.The results pointed out that the passive film evolves from mixed Fe–Cr magnetite-type structure, towards a more oxidized iron rich layer with different Cr distribution as the immersion time in chloride solution increases. Samples having higher roughness show more oxidised oxide layers at a given immersion time, which can indicate major oxygen availability at the interface level. Moreover, chlorides ions do not penetrate the film that dissolves in a very heterogeneous way.