In-situ Raman spectroscopy study of iron and carbon steel corrosion in mineral water

Abstract The corrosion behaviour of iron and carbon steel in mineral waters has been studied at open circuit potential or cathodic polarisation thanks to in-situ Raman spectroscopy. Corrosion process is not modified whatever the conditions (even with complete deaeration of the electrolyte). Pitting, associated with green rust formation, occurs in all cases at open circuit potential. Pitting is clearly associated with impurities in the metal and developed around sulfide (in carbon steel) or silicates (in iron). Evolution of green rust towards more stable iron compounds depends on the electrolyte conditions. Formation of an insulating barrier of a calcium (or magnesium) salt (silicate in acidic, carbonate in basic) has been analysed during cathodic polarisation. However dissolution of iron as Fe 2+ ion is not totally stopped and siderite (iron II carbonate) or iron II sulfate has been founded underneath this layer.