An XPS Investigation of Passive Film Formation on a Maraging Stainless Steel

The composition and structure of passive films formed on 00Cr13Ni4Co4Mo4W2Ti maraging stainless steel in acidic solution were studied by XPS. The results show that the pitting resistance of the steel in 3.5% NaCl solution was greatly improved. The pitting potential was increased form 332 mV to 439 mV(SCE) after passivation treatment. The passive films were composed of an outer layer and an inner layer. The outside passive film of the maraging stainless steel was mainly composed of Cr2O3, CrOOH or Cr(OH)3 and FeOOH .The inside film was mainly composed of Cr2O3 and FeO. The enrichment of Ni and Mo in the bottom of the passive film can avoid the reduction of the passive film, increase the stability of the passive film, and improve the corrosion resistance of the maraging stainless steel.