External Corrosion Assessment in a LNG Pipeline

Abstract A 16 inch, diameter LNG pipeline which transports 54 MBPD between extraction and fractionation facilities located north-east of Venezuela, showed an accelerated external corrosion even though coating and cathodic protection had been used to protect it. A diagnosis of the external condition of the pipeline was addressed by matching the results obtained by using different techniques such as electromagnetic pigging, DC voltage gradient survey, close interval potential survey, soil classification and resistivity profiles along the pipeline. This paper discusses the factors evaluated to identify sections of the pipe where corrosion problems occurred under disbonded pipeline coating, which required immediate attention for coating rehabilitation.