The corrosion behaviour of AISI 304 stainless steel in 0.1 M HCl at room temperature—III. The effect of sensitization

This work describes the results of a study concerning the influence of sensitisation upon the corrosion behavior of an AISI 304 in 0.1 M HCl at room temperature. Electrochemical tests show that sensitized steel requires long periods of time in order to reach quasi-stationary conditions, and that there is no potential field that guarantees a negligible propagation of the corrosive attack. Behavior in the passive state can depend upon behavior in the active region, due to the formation of corrosion products which are capable of inhibiting the anodic process, and of preventing the formation or facilitating the local destruction of passivity films. The metallurgical heterogeneity resulting from steel sensitization promotes the formation of inhibiting products in the active region, thus preventing a state of stable passivity to exist. The improvement in resistance to localized corrosion when molybdenum is added as an alloying element, is attributed, at least in part, to a reduction in the corrosion rate in the active region.