EffEcts of WElding HEat input on MicrostructurE and corrosion cHaractErization in cgHaz of X80 pipElinE stEElThe coarse-grained heat-affected zone specimens of X80 pipeline steel were produced by welding thermal simulation under different heat inputs of 10, 30, and 55 kJ/cm to study the effects of heat input on microstructure evolution and corrosion characterization. The corrosion resistance of coarse-grained heat-affected zones was poorer than that of base metal due to less homogenous in the former. For 10 kJ/cm coarse-grained heat-affected zone, the corrosion resistance was poorer than the others due to the more adsorption hydrogen around the needle-like martensite/austenite constituents and greater galvanic driving force between the needle-like martensite/austenite constituents and ferrite. in carbonate/bicarbonate solution, better corrosion resistance for coarsegrained heat-affected zones was obtained when the heat input is 30 kJ/cm, which can be attributed to the severe coarse martensite/ austenite constituents for 55 kJ/cm coarse-grained heat-affected zone. in the h 2 S environment, the better corrosion resistance for coarse-grained heat-affected zone was obtained when the heat input is 55 kJ/cm, which can be attributed to the protective effect of corrosion products. in addition, the high content of M/a constituents for 30 kJ/cm CghaZ was good for hydrogen adsorption, which was adverse to the corrosion resistance in acid environments.