Abstract: Two welding heat input were applied to 16Mn and X70 steel by SAW. The corrosion behavior of weld metal was investigated in two kinds of solution, NACE and 3.5% NaCl, respectively. The results show that corrosion tendency of acicular ferrite (AF) in weld is greater than other microstructures, but its corrosion velocity is slowly. The corrosion resistance of weld metal with AF increases with the increasing of acicular ferrite fraction, but too much acicular ferrite raicrostructures leads to accelerate corrosion of weld in HSLA.