ABSTRACT: Supermartensitic stainless steels deduced from the refinement of the composition of martensitic steels, have a low carbon content with 13% chromium, 5% nickel and 2% molybdenum, this new generation of steel has an improved ductility with good mechanical strength and excellent corrosion resistance. The objective of this paper is to prove this resistance to hydrogen diffusion in the austenitic phase, and to study the resistance to sulfate corrosion and chloride pitting. The corrosion properties will be discussed in relation to their metallurgical microstructure. Stationary (polarization curves) and transient (electrochemical impedance) electrochemical methods were applied. The corrosion rate as a function of time was determined by the mass loss method and the characterization of the surface state was studied by optical microscopy. Two types of corrosion were observed: a uniform corrosion in which the half-reactions are homogeneously distributed in 0.5M H2SO4, followed by a loca

Keywords: Martensitic steel, supermartensitic steel, electrochemical impedance, corrosion