The effect of pre-corrosion and steel microstructure on inhibitor performance in CO2 corrosion

The importance of chemical composition and microstructure on CO2 corrosion of carbon and low alloy steels has been widely recognized, still contradictory results can be found in the literature. The aim of this work is to assess the relationship between microstructure, surface condition and inhibitor efficiency in CO2 corrosion. A C-Mn steel with two different microstructures was tested in a deoxygenated 5% wt. NaCl solution saturated with CO2 at 40 deg C, pH 6. A commercial imidazoline-based inhibitor was added after different pre-corrosion periods. The results obtained showed that pre-corrosion decreases the inhibitor efficiency, but that its impact is microstructure dependent.