The effect of an impinging liquid-solid jet on the electrochemical corrosion of stainless steels

Stainless steels rely on their passive film for corrosion protection in sal ine environments and localised disruption of the passive film can lead to h igh local rates of material loss. Materials which exhibit passivity in stat ic conditions are often susceptible to erosion-corrosion under severe hydro dynamic regimes. In this paper the corrosion behaviour of two superaustenit ic (UNS S31254 and UNS S32654) and one superduplex (UNS S32750) stainless s teels was examined in static conditions at a range of temperatures from 18 C to 70 C and during exposure to an impinging saline jet containing varying concentrations of solid particles. In static conditions the materials exhi bit decreasing resistance to passivity breakdown as the temperature is incr eased and a critical breakdown temperature for UNS S31254 and UNS S32750 wa s identified. Under liquid-solid impingement the materials exhibit an activ e regime near to the free corrosion potential followed by a stabilised curr ent regime as more positive potentials. The complex electrochemical respons e is dependent on the material grade and the solid particle concentration. Also in the paper assessment of the 'recovery' of the stainless steels afte r exposure to slurry impingement is addressed.