The influence of steel microstructure, pre-corrosion period and 1 %Cr content addition on CO2
corrosion susceptibility of C-Mn steels and on the inhibitor performance has been studied. In a previous
paper, we have shown that the addition of 1 %Cr has a remarkable detrimental effect on inhibitor
performance1.
Two carbon steels with two different microstructures (annealed, and quenched and tempered
(Q&T)) were tested in a deoxygenated 5% wt. NaCl solution, saturated with CO2 at 40 °C, pH 6. The
performance of a commercial imidazoline-based product to control CO2 corrosion was studied by
means of electrochemical measurements employing a.c. and d.c. techniques. The inhibitor was added
after 24 hrs pre-corrosion period or before electrode immersion (no pre-corrosion). Surface film
characteristics were studied by means of SEM and EDX.
The results show the detrimental effect of pre-corrosion and Cr addition on inhibitor efficiency. It is
also shown that the pre-corrosion impact depends on microstructure and chemical composition.