Passivation behaviour of Alloy 31 (UNS N08031) in polluted phosphoric acid at different temperatures

• Published in: Corrosion science 2012-03, Vol.56, p.114-122
• Main Authors: Escrivà-Cerdán, C., Blasco-Tamarit, E., García-García, D.M., García-Antón, J., Guenbour, A.
• Format: Article
• Language: English
• Subjects: A. Acid solutions; A. Stainless steels; Applied sciences; C. Passivity; Chlorides; Corrosion; Corrosion environments; Exact sciences and technology; Metals. Metallurgy; Passivation; Phosphoric acid; Protective
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2011.11.014

► Potentiodynamic polarisation curves were characterised by a very wide range of passivity. ► The passivation index, n decreased in the temperature range of 20–80 °C. ► Applied potentials between 300 and 800 mV Ag/AgCl have no effect on the parameter n. ► When applied potential is close to E b (≈1000 mV Ag/AgCl) the passivity is worst. ► Alloy presents high corrosion resistance in solutions similar to industrial process. The influence of temperature (20–80 °C) and chloride concentration (0.06–0.42 wt.% KCl) on the electrochemical behaviour of the UNS N08031 was studied in 40 wt.% polluted phosphoric acid solution. Passivation behaviour was investigated by using potentiostatic tests at different potentials. From the linear regions of the log i vs. log t transients, the parameter n was obtained. The results showed that the applied potential hardly affects on the passivation rate n. However, n values decreased when temperature increased. The values of n demonstrated that the passive film formed on Alloy 31 was compact and highly protective.