Gas Metal Arc Welding (GMAW) Flux Cored Arc Welding (FCAW) Metal Cored Arc Welding (MCAW) Practice Test

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Which of the following is NOT a common cause of porosity in GMAW?

Moisture in electrode

Oil or grease on base metal

Rust or contamination

Excessive cleaning of base metal

Porosity in GMAW happens when gas gets trapped in the weld as it cools, with hydrogen being a common culprit. Moisture in the electrode can release hydrogen when heated, oil or grease on the base metal introduces hydrogen and other contaminants, and rust or surface contamination can create gas pockets or disrupt shielding, all leading to pores. Cleaning the base metal helps remove these contaminants, so excessive cleaning doesn’t typically cause porosity and can actually improve weld quality. Therefore, excessive cleaning of the base metal is not a common cause of porosity.