Corrosion of 2·25Cr–1Mo ferritic steel in subhuric acid and sea water

Abstract

The corrosion behaviour of 2·25 Cr–1 Mo ferritic steel in different concentrations (0·05–5N) of sulphuric acid and in sea water has been studied by potentiodynamic polarization measurements at scan rates of 45 mV min^-1 The experiments were performed on steels in two different conditions, cold worked and annealed at 850°C for 2 h in vacuum (0·1 Pa), and the effect of microstructure was also analysed. The annealed samples show better corrosion resistance than cold worked ones, in both sulphuric add and sea water. The passivation current, passivation potential, and corrosion current all increase with increasing acidity, while the corrosion potential decreases. The effect of sulphuric acid concentration is more pronounced at concentrations up to 2N. The present results are compared with available literature data for iron and iron–chromium alloys with different Cr contents in sulphuric acid media. No passivation was observed in sea water.