Traditional techniques used to evaluate the performance of corrosion inhibitors utilize rotating cage autoclaves (RCA) or immersion tests that may require 21 days to complete the test to get meaningful localized corrosion data. In this paper, cyclic polarization (CP) and electrochemical impedance spectroscopy (EIS) techniques were used to investigate the corrosion inhibition of carbon steel in the presence of carbon dioxide with different anti-agglomerant low dose hydrate inhibitor/corrosion inhibitor (LDHI/CI) combination products. Electrochemistry measurements were carried out with rotating cylinder electrode (RCE) equipment to assess the effectiveness of the products under turbulent flow. General corrosion rates and polarization resistance values were calculated from the CP and EIS scans and compared against coupon weight loss and white light interferometry (WLI) pitting data for selected experimental conditions and showed good agreement. The results obtained in this work proved that electrochemistry techniques such as EIS and CP can serve as high-throughput techniques to predict the relative ranking of corrosion inhibitor actives as reliably as the longer-term like immersion or autoclave tests.
Corrosion inhibitors (CI) are typically evaluated using either short-term electrochemical methods or long-term weight loss methods in laboratory set up. Although electrochemical methods provide fast and real-time corrosion information, corrosion subject matter experts, in general, rely on long term weight loss methods to determine localized corrosion information. These long-term methods include exposure of the metal coupon in a corrosive media under specific field conditions/parameters such as temperature, pressure, wall shear stress, corrosive gas species and test length in the presence of corrosion inhibitor active(s). Once the corrosion performance test has been performed, the post-test metal coupon weight loss and pit density and depths are determined. These corrosion performance tests provide reliable data, but the test duration is long (7-28 days), which delays the qualification of corrosion inhibitors and the delivery of results. As an alternative to these long-term corrosion performance tests, cyclic polarization (CP) was considered as a suitable and sophisticated technique that can predict pitting tendencies in shorter duration.
