Effect of temperature on passive film formation of UNS N08031 Cr–Ni alloy in phosphoric acid contaminated with different aggressive anions

The influence of temperature and the effect of aggressive anions on the electrochemical behaviour of UNS N08031 stainless steel in a contaminated phosphoric acid solution were evaluated. Stabilisation of the passive film was studied by potentiodynamic polarisation curves, potentiostatic tests, electrochemical impedance spectroscopy (EIS) measurements, Mott–Schottky analysis and X-ray photoelectron spectroscopy (XPS). The stability of the passive film was found to decrease as temperature increases. The film formed on the stainless steel surface was a n-type semiconductor and the XPS spectrum revealed the presence of fluoride ions.