THE INFLUENCE OF Cr CONTENT ON THE EFFICIENCY OF INHIBITOR OF C-Mn STEEL CO2 CORROSION

L. PAOLINELLI; T. PEREZ; S.SIMISON

San Diego, CA, USA

Conferencia; CORROSION 2006; 2006

NACE International

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.  Keywords : CO2 corrosion; steel microstructure; corrosion inhibitor; imidazolines, chromium.