Tests have been carried out in the laboratory to study two different CO2 corrosion inhibitors; one amine based inhibitor (ABI) and one imidazoline-based inhibitor (IBI) using a variety of electrochemical techniques. Both inhibitors are considered for application in the North Sea for reducing the CO2 corrosion problems in the pipelines carrying oil and gas.
It was found in glass cell experiments that the temperature and pH had a negligible effect on the performance of both inhibitors. The presence of NaCl degraded the performance of the ABI but did not affect protectiveness obtained with the IBI. A condensate oil did not interfere with performance of the inhibitors. However, a crude oil degraded the performance of the ABIO significantly. It was found that the IBI corrosion inhibitor was incompatible with a phosphinocarboxylic acid based scale inhibitor. The performance of IBI was very poor in the presence of the surface films. Finally, the mechanism of protection for both inhibitors was explained with a model including a Frumkin-type adsorption isotherm and a surface blockage effect.