A comparative study of gravimetric and electrochemical techniques for the evaluation of corrosion inhibitor activity onset and efficiency in pipeline CO2 environments

Abstract

The monitoring of internal corrosion of pipelines is a critical element of the pipeline maintenance programs. A benchmarking study of enhanced techniques for real-time corrosion monitoring such as Linear Polarization Resistance and Harmonic Distortion Analysis was performed, enhanced Electrical Resistance in conjunction with standard metal coupon. The transition of the corrosion processes occurring in metals immersed in corrosive electrolytes at the onset of inhibitor action after its injection was found a revealing item for study. This study considered a 3% NaCl solution with and without 10% diesel, saturated with CO2 at 50 ºC and standard AISI 1018 coupons. A set of generic corrosion imidazoline-based inhibitors was studied. The benefits of employing real-time corrosion monitoring devices include shortened test times, increased number of inhibitors evaluated, and an increase in data quality and quantity. Results show that the corrosion rates from linear polarization resistance in the solution without inhibitor were overestimated, while the Harmonic Distortion Analysis and enhanced Electrical Resistance presented similar results to Standard Coupon. The enhanced electrical resistance monitoring also proved to be a good device to reveal the onset of corrosion protection after the inhibitor is applied.