The influence of steel microstructure, and 1% Cr content addition on CO2 corrosion susceptibility of C-Mn steels and on the inhibitor performance has been studied.

A 1% Cr low alloy steel with two different microstructures (ferrite-perlite and tempered martensite) was tested in a deoxygenated 5% wt. NaCl solution, saturated with CO2 at 40 °C, pH 6. Comparisons with previous results obtained with a C-Mn steel have also been performed.

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 a pre-corrosion period of 72 hrs. Surface film characteristics were studied using SEM and EDX.

Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization Resistance (LRP) studies showed that Cr addition has a remarkable detrimental effect on the efficiency of the studied inhibitor. A microstructure influence was also observed (the tempered martensite structure presented a better performance compared to ferrite-perlite one), but the effect is secondary to that of Cr, In addition, pre-corrosion decreases efficiency and its impact is also microstructure dependent.

Subject
Steel surfaces, Inhibitor performance, Composition, Corrosion rate, Microstructure, Chromium, Free corrosion potential, Precorrosion, Corrosion products, Chemical inhibition, Film formation, Corrosion inhibitors, Steel
Keywords:
CO2 corrosion, steel microstructure, corrosion inhibitor, imidazolines, chromium
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2006
Association for Materials Protection and Performance (AMPP)
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