Erosion — corrosion of duplex stainless steel under Kuwait marine condition

Abstract

Erosion — corrosion of stable passive metals like Duplex Stainless Steels (DSS) proceeds by the repeated removal and repair of the oxide film. When sand particles are entrained it can be a problem in marine pumps, piping systems, heat exchangers, and units handling seawater in the Arabian Gulf for use as part of desalination plants. More specifically, sand particles in the presence of seawater enhanced the erosion corrosion problem. If the passive film structure is stable, it will reform spontaneously when it becomes damaged. The erosion-corrosion study is concerned with the application of a jet impingement apparatus to study the behavior of DSS steel of Cr/Ni/Mo/N grade in simulated Arabian Gulf seawater. An interference color imaging technique (ICI) for thickness measurement of the oxide film passivity, pitting, and transpassivity of the surface of DSS has been developed under the effect of well defined hydrodynamic condition and potentiodynamic polarization technique. Electrochemical imaging technique of surface corrosion potential mapping (SCM) was also introduced to measure the rate of repair of the passive film combined poteniodynamic polarization under flowing conditions, both with and without the addition of sand particles. The main aim is to obtain a better understanding of the electrochemistry of DSS alloys in marine erosion–corrosion condition and to examine the viability of SCM and ICI to be used as a diagnostic tool for DSS material evaluation. The results indicated that both techniques gave optimum imaging analysis of DSS steel. Water jet impingement showed higher current densities at the ferrite dissolution potential and austenite pitting potential during the introduction of sand particles.