Pitting corrosion resistance of sensitized type 2205 duplex stainless steel in hot concentrated seawater

摘要

Pitting corrosion resistance of 2205 duplex stainless steel aged at 850 degrees C was investigated in the hot concentrated seawater (i.e., the simulated low-temperature multi-effect distillation environment) by optical microscopy (OM), scanning electronic microscopy (SEM), and electrochemical measurement techniques. The precipitation of the sigma phase leads to sensitization in the specimens during the aging treatment. The degree of sensitization (DOS) presents a maximum value with the change of sigma phase content. The pitting corrosion resistance of the specimens degrades markedly in the presence of very weak sensitization. The pitting potential decreases almost linearly with the logarithm of DOS. The pit propagation mainly takes place along the Cr-depleted region around the sigma phase. The repassivation ability of the specimens changes insignificantly with the aging time.