Aspects of selective and pitting corrosion in cast duplex stainless steels

Duplex stainless steels are excellent materials for industrial applications and their use has increased in the oil, chemical, petroleum (offshore), and electric power industries. Pitting resistance equivalent (PRE) is the first parameter used to characterise the pitting and crevice corrosion resistance. Nevertheless, there are other aspects to be considered, such as the precise values of the PRE in the α and γ phases and the selective corrosion processes that may occur at grain boundaries. This paper indicates that α/γ and α/σ interfaces are preferential sites for the nucleation and growth of pits and for consequent selective corrosion, with increasing tendency in the ferritic phase. In addition, the selective dissolution potential is more reactive (and therefore, is of greater significance) than the pitting potential.