Abstract: Since the welded joint of carbon steel is corroded seriously in the ammonium sulfite, corrosion behavior of welded joint welded by arc welding with J422 electrode containing different contents of Ni has been studied by means of three electrode galvanochemistry test and metallurgical structure analyses.The results show that the addition of Ni causes the grain refinement of the weld and the decrease of acicular ferrite.In addition, the polarizability of the weld increases and the corrosion current decreases in the ammonium sulfite.The welded joint containing 1.2 wt% Ni has the lowest corrosion rate.