Evaluation of Impressed Current Cathodically Protected Tank Bottoms in the Presence of Vapor Phase Corrosion Inhibitor

摘要

This work aims to assess the effectiveness of an amine carboxylate-based vapor phase corrosion inhibitor (VCI) on the protection of storage tank bottoms against soil-side corrosion, as standalone and in combination with an impressed current cathodic protection (ICCP) system. It also attempts to determine the effect of VCI on instant-off potential. Lab-scale tanks simulating the environment of single bottom storage tanks sitting on washed sand with a high-density polyethylene (HDPE) liner and ICCP system were considered. The corrosion rate for each tank was monitored using an electrical resistance probe corrosion monitoring system. Natural and instant-off potentials of tank bottom steel plates were also monitored throughout the experiment using a temporary copper/copper sul-fate (Cu/CuSO_4) reference electrode. Corrosion rate data from electrical resistance probes indicated that amine car-boxylate VCI slurry is effective in mitigating corrosion on carbon steel bottom plates. The corrosion rate was reduced by 82.5% and 89.7% as standalone and in combination with ICCP, respectively. The study also indicated a shift of the instant-off potential, which might need to be considered by CP operators in the case of using a VCI in supplementing ICCP for protection of storage tank bottoms.