Analysis of Pitting Corrosion of Pipelines in a Marine Corrosive Environment Using COMSOL Multiphysics

In this work, we have developed a pipeline model made of 316 stainless steel considering the pipeline is subjected to a marine corrosive environment (seawater) and investigated pitting corrosion behaviour inside the pipeline with the help of COMSOL Multiphysics software. The extent of pitting corrosion was investigated by examining the electrochemical parameters such as electrolyte potential and electrolyte current density and explored the effect of variation in number of pits on the corrosion behaviour. Electrolyte potential distribution reveals that electrolyte potential variation along the pit surface is small and the value found to be highest at the pit- electrolyte interface. Thus, confirming that the pit electrolyte interface is more susceptible to corrosion. Electrolyte current density distribution showed that electrolyte current density value is highest at the pit, which is 314 A/m2 in case of single 3-D pit suggesting that the pit surface corroded heavily. In the case of multi-pit electrolyte current density distribution, the electrolyte current density computed to be 171 A/m2 and 106 A/m2 in double and triple pits, respectively. The obtained current density values have been used to calculate corrosion rate with the help of Faraday’s law. The multi-pits models are showing the corrosion rate of 195.7 mm/year and 121.3 mm/year for double and triple pit, respectively, which are comparatively lower than that of single pit (corrosion rate of 359.3 mm/year) due to increase in the area of anode surface.