Crevice corrosion affects the integrity of stainless steels used in oil and gas components exposed to seawater. Traditionally, crevice corrosion testing involves the use of artificial crevice formers to obtain a critical crevice potential, which is a measure of the crevice corrosion resistance of the alloy. The critical acidification model proposed by Prof. J.R Galvele predicts that the critical crevice potential is the minimum potential required to maintain a sufficiently acidic solution inside either a pit or a crevice. Application of Galvele’s model requires an estimation of both the diffusion length and the i vs. E behavior of the metal in the solution inside the crevice.
In this work, the crevice corrosion resistance of a 22-Cr duplex and a 25-Cr super duplex stainless steels (UNS S31803 and UNS S32750, respectively) were investigated. The i vs. E response of the two stainless steels was determined in acidified solutions of various chloride concentrations, which simulate those at an active crevice. Critical potentials predicted by the critical acidification model were compared with critical crevice potentials measured in simulated seawater.
Keywords: downloadable, UNS S32750, UNS S31803, simulated crevice solutions, crevice corrosion, seawater