(735av) Study of Galvanic Corrosion of Mild Steel Coated with AZ91D Magnesium Alloy By Comsol Multiphysics

Pipeline corrosion causes annually about $1.3 billion of loss in the world economy. It weakens the integrity of the pipeline and increases the risk of leaks and spills that result in significant safety hazards to the community. The replacement or repair of pipes is also expensive and the associated downtime as a result of the corrosion causes loss of industrial production. Corrosion of pipelines carrying flammable gases or liquids can cause fires or explosions. The release of toxic substances due to pipeline corrosion can result in respiratory problems, skin irritation etc. Pipeline collapse due to corrosion can cause property damage, injuries, and loss of life. A mathematical model of pipeline corrosion will help bridge the gap from “post-corrosion” measurement to proactive corrosion prevention and management, revolutionize the practice of corrosion management, enhance the reliability of midstream assets, improve operational efficiency and reduce potential environmental risks

This talk will present a mathematical model to study galvanic corrosion between steel pipe wall and AZ91D magnesium alloy coating immersed in 5 wt% aqueous NaCl solution. Galvanic corrosion for pipes of different sizes, such as 10 and 12” schedule 40 and 80 pipes coated with different coating thickness ranging from 1/16 to ½” were studied by a finite element analysis (FEA) mathematical model developed using COMSOL Multiphysics. It was found that, as the radius of the holes and the total radius of the pipe decreased, corrosion rate increased. Also, it was observed that, with the increase of magnesium alloy coating thickness, interfacial potential between the outer surface of the pipe and the surrounding solution increased proportionally, however, the galvanic corrosion potential between pipe and magnesium alloy did not change significantly. This increase of interfacial potential was shown in the current density as interfacial potential increased with magnesium alloy coating thickness current density decreased due to the increase of resistance.