The influence of steel microstructure, chemical composition and pre-corrosion on CO2 corrosion inhibitor efficiency

L. PAOLINELLI; T. PÉREZ; S. SIMISON

Nashville, Tennesee, USA

Congreso; Corrosion 2007; 2007

NACE

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