Mechanical and electrochemical properties of a cast carbon steel. Part 2: Behaviour in corrosion

Author(s): Patrice Berthod, Elodie Conrath

A ferrito-pearlitic steel, elaborated by foundry with a cylindrical shape has been mechanically studied in compression and hardness in a first part of the present work. In this second part the equivalent samples were tested in corrosion in a sulphuric acid solution by varying both the initial deformation rate and the cutting orientation with respect to the sample axis. Stern-Geary linear polarizations were successively run during half an hour of immersion with recording of open circuit potential and polarization resistance, while cyclic polarizations were performed between the cathodic domain and the anodic solvent’s wall. No systematic differences were noted on the cyclic polarization curves between the values, obtained for the different deformation rates and orientations, of the various parameters describing the corrosion state changes (active  passive and passive  active), although that some tendencies were seen. In contrast the linear polarization runs showed that the Rp value more clearly depends on both the hardening amount and the surface orientation. It was notably found again that the polarization resistance decreases, and the deduced corrosion rate increases, when the plastic relative deformation is higher, and also, by combining the present results with previous ones, that there is possibly a continuity of evolution of the parallel/perpendicular Rp order from the negative deformations in compression to the positive deformations in traction.

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