HAZ corrosion of 22SiMn2TiB ultra-strength steel weldment in 3.5%NaCl solution

Weld heat-affected zone (HAZ) microstructures of 22SiMn2TiB ultra-strength steel were thermally simulated by means of Gleeble-1500 machine. Polarization measurement of the quenched zone and tempered zone in 3.5%NaCl solution was conducted respectively with potentiostat/galvanostat Solaron SL1280B. The relation between the microstructure and the HAZ corrosion resistance in 3.5%NaCl solution was established. Carbon and boron diffusions, segregation and iron carbide or boride precipitation are dependent on simulated weld thermal cycle peak temperature θ_max and continuous cooling time t_8/5 and induce the microstructure transformation. The polarization curves and corrosion potentials of the simulated HAZ with different microstructures in 3.5%NaCl aqueous solution are slightly different, and the limit diffusion current of dissolved oxygen in 3.5%NaCl solution decides corrosion current. Weld bond, which undergoes anodic dissolution in couple corroding, needs to be protected carefully.