Effects of hydrogen and tensile stress on the breakdown of passive films on type 304 stainless steel

The effects of hydrogen and applied tensile stress on the breakdown of pass ive films on Type 304 stainless steel have been investigated in chloride-co ntaining solutions. Hydrogen was cathodically introduced into specimens by applying a constant current density. The current responses to the applicati on of a passivation potential of 0.3 V versus a saturated calomel electrode (SCE) and additions of various concentrations of chloride ions were record ed. Hydrogen greatly decreases the critical chloride concentration for the breakdown of passive films, which indicates that hydrogen promotes the brea kdown of passive films. Hydrogen is also found to hinder the repassivation process. With an increase in applied tensile stress, the critical chloride concentration for the breakdown of a passive film decreases. The critical c hloride concentrations are always significantly lower for charged specimens than for uncharged specimens at the applied tensile stress range and the e ffect of stress on lowering the critical chloride ions is more significant for charged specimens than uncharged specimens. (C) 2001 Elsevier Science L td. All rights reserved.