THE INFLUENCE OF STEEL MICROSTRUCTURE, CHEMICAL COMPOSITION AND PRE-CORROSION ON CO_2 CORROSION INHIBITOR EFFICIENCY

摘要

The influence of steel microstructure, pre-corrosion period and 1 %Cr content addition on CO_2 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 performance~1. 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 CO_2 at 40°C, pH 6. The performance of a commercial imidazoline-based product to control CO_2 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.