Effect of Field Operational Variables on Internal Pitting Corrosion of Oil and Gas Pipelines

Experiments were conducted in six operating oil and gas production pipelines over four years to determine internal pitting corrosion. rates under realistic operating conditions. -Pitting corrosion rates were similar when the compositions of surface layers were similar. -When a compact: layer of single species formed. the surface was protected from pitting corrosion: the iron sulfide (FeS) layer was more protective than the siderite (FeCO3) layer. -When multiple layers of several species formed, the susceptibility of the surface to pitting corrosion increased. Frequent changes in the pipeline operating conditions facilitated the formation of multiple layers. -When no surface layer formed, the susceptibility of the surface to pitting corrosion decreased but was not eliminated. Extraneous materials (e.g., sand) on the surface facilitated pitting corrosion. -In the absence of surface layer and extraneous materials, no pitting corrosion was observed.