The effects of hydrogen on the breakdown of passive films formed on Type 304 stainless steel

The effects of hydrogen on the breakdown of passive films formed on Type 30 4 stainless steel were investigated. Cyclic potentiodynamic polarization me asurements revealed that hydrogen decreases the breakdown and protection po tentials, indicating an increase in pitting susceptibility. An increase in pitting susceptibility due to hydrogen was confirmed by immersion tests and potentiostatic measurements: hydrogen in passive films increases pit densi ty and decreases the initiation time for the film breakdown. The critical c hloride concentration for the film breakdown decreases with the charging cu rrent density. Hydrogen also hinders the repassivation process once the fil m is broken down. Several possible reasons are postulated to explain the ef fects of hydrogen on the film breakdown. (C) 2000 Elsevier Science S.A. All rights reserved.