Semiconductor Characters of Passive Film on AISI304 Stainless Steel Surface in Electrolytes during Corrosion Process

The semiconductor characters of AISI304 stainless steel′s passive film during corrosion process in three typical electrolytes were investigated by using potential-capacitance measurement and Mott-Schottky analysis.Passive film on the surface of the stainless steel was constructed from two different types of semiconductor film in electrolytes under study.In sodium hydroxide,the semiconductor-type-transition potential had an obvious negative drifting,while in the other two electrolytes,the transition potential had no obvious change with immersion time.Charge carrier density in the passive film increased with immersion time.The charge carrier density at 1000Hz in these three solutions could be listed in an ascending order of sodium sulfate,sodium hydroxide and sulfuric acid.Frequency dependence,appeared in all Mott-Schottky plots of AISI304 stainless steel's passive film,could be attributed to the time effect in generation-recombination process of charge carriers.The main cause of passive film's corrosion on the stainless steel surface in sodium hydroxide solution was the rising conductibility of chromium-rich layer,while in the other two solutions it was due to the ascending conductance of iron-rich layer.