Carbonation-corrosion resistant behaviour of corrosion-resistant steel Cr10Mo1 and its protection mechanism

Abstract

The electrochemical response of new alloy corrosion-resistant steel Cr10Mo1 passivated under attack of carbonation (pH from 13.3 to 9.0), was evaluated by electrochemical techniques (linear polarization resistance, and electrochemical impedance spectroscopy). X-ray photoelectron spectroscopy (XPS) was used to characterize the composition and structure of the surface film on the steel. The results show that as carbonation progressing, the corrosion-resistant steel never goes to corrosion domain even when pH falls to 9.0，but has an increasing corrosion resistance. According to XPS analysis, the passive film on the corrosion-resistant steel presents a bilayer structure: an outer layer enriched in Fe oxides and hydroxides, and an inner layer rich in Cr species. As the pH decreases, Fe oxides gradually decompose while more stable and protective Cr oxides get enriched in the film. Under carbonation attacking, the increasing Cr oxides in the film act as a protection barrier to the steel corrosion and support the corrosion-resistant steel still good passivity.