Corrosion behavior of supermartensitic stainless steel in aerated and CO2-saturated synthetic seawater

This paper discusses the corrosion behavior of supermartensitic stainless steel in CO2-saturated synthetic seawater. A comparison is also made with an aerated solution. Potentiodynamic polarization measurements were taken in synthetic seawater with five different chloride contents: 20 000, 30 000, 40 000, 60 000 and 80 000 ppm, and at three different temperatures: 5, 25 and 60 degrees C. The pitting potential decreased in a logarithmic relation with the chlorine concentration. The pitting potential decreased linearly with increasing temperature. XPS measurements indicated that the presence of CO2 enriches the Cr content in the oxide layer and that the temperature also favors this enrichment. The pitting potential depends on the stability of passive film. Otherwise, stability is dependent on the composition. So pitting potential is affected by a synergy between the chloride concentration and the saturated CO2 solution. (c) 2006 Elsevier B.V. All rights reserved.