Imposed potential measurements to evaluate the pitting corrosion resistance and the galvanic behaviour of a highly alloyed austenitic stainless steel and its weldment in a LiBr solution at temperatures up to 150 °C

Pitting corrosion resistance and galvanic behaviour of Alloy 31, a highly alloyed austenitic stainless steel (UNS N08031), and its weldment were studied in a heavy brine LiBr solution 1080 g/l at different temperatures (75–150 °C) using electrochemical techniques. The Mixed Potential Theory was used to evaluate the galvanic corrosion between the base and welded metals. Cyclic potentiodynamic curves indicate that high temperatures make passivation and repassivation of pits difficult, because the whole passivation range and the repassivation potential values decrease with temperature. The critical pitting transition occurs between 100 and 125 °C.

Research highlights
► The CPT transition was between 100 and 125 °C.
► Studied materials repassivated after the breakdown of the passive film even at 150 °C.
► Corrosion current densities increased with temperature following the Arrhenius equation.
► The pitting corrosion resistance of materials decreases with temperature.
► Temperature makes passivation of metals and repassivation of pits difficult.