Effectiveness Evaluation of Vapor Corrosion Inhibitors for Tank Bottom Plate Corrosion Control

摘要

Soil-side corrosion of above ground storage tank bottoms is a major challenge for midstream operators owning tank farms. In North America, most above ground storage tanks include active cathodic protection (CP) systems to protect the soil-side of the tank bottoms from corrosion. However, CP systems could fail leading to unprotected tank bottom, and occasionally extensive corrosion has been observed even with an active CP system in place. In addition, a tank bottom without a CP system could experience elevated corrosion including pitting corrosion. Vapor corrosion inhibitors (VCIs) are being promoted as alternative corrosion control measures. An industry-sponsored study was conducted to evaluate effectiveness of the VCIs in mitigating the tank bottom corrosion. Specifically, the study was conducted to determine whether the VCIs are effective in mitigating corrosion comparable to a working CP system for tank bottoms or not. Several laboratory-scale experiments were conducted, and experimental data were rigorously analyzed. It was found that the VCIs are effective in mitigating corrosion when vendor specific recommended dosages are used. The pitting corrosion significantly decreased with application of the VCIs, but corrosion rates were not mitigated to the extent specified in NACE SP0193 and NACE SP0169 for demonstrating adequate CP.