Influence of the microstructure on the corrosion behaviourin a sulphuric solution of cast carbon steels as characterized by electrochemical impedance spectroscopy. Part 1: Effect of the carbon content

摘要

The behaviour of carbon steels may depend on their microstructure, notably of their fraction in cementite which is piloted by the carbon content and of a previously underwent hardening. The case of the mechanical properties is well-known but the influences of the carbon content/cementite fraction and of an earlier plastic deformation on the corrosion behaviour is not necessarily so well determined. In this first part this is the carbon content which is under focus. A series of four binary Fe-C alloys, with C contents spread over the eutectoid composition, were elaborated following strictly the same synthesis parameters to avoid any perturbation of other factors such as various microstructure finenesses or presence of minor elements. Their behaviour in a model sulphuric acid solution was specified by spectroscopy of electrochemical impedance. Several differences were observed between on one hand the ferritic steel and on the other hand the three cementite-containing steels, concerning the evolution of the Nyquist half circle, the transfert resistance and the double layer capacity.