Corrosion behaviors of 304 stainless steel joints brazed with Sn-electroplated Ag brazing alloys

To reveal the corrosion behavior of 304 stainless steel brazed joints in NaCl solution, the high Sn content of AgCuZnSn brazing alloys was prepared successfully by electroplating and thermal diffusion process. 304 stainless steels were induction brazed by using the prepared brazing alloys. 3.5% NaCl solution at the temperature of 60 ℃ was used to simulate seawater environment and determine the localized corrosion characteristic of 304 stainless steel brazed joints. The corrosion morphology was observed with scanning electron microscopy (SEM). The results showed that corrosion groove was found on the interface region between 304 stainless steel and brazing seam when the brazed joints were dipped in the solution of 3.5 % NaCl for 2.5 h. The serious corrosion phenomenon happened and a wide range of defects such as holes and cracks occurred on the surface of the 304 stainless steel, while almost no corrosion defects occurred in the brazing seam zone and Cu-rich phase was corroded preferably. The corrosion rate of brazing seam and base metal initially increased and then decreased with the increase of corrosion time. The corrosion rate of brazing seam was slightly lower than that of base metal. The average corrosion rates of brazing seam area and 304 stainless steel were 0.098 and 0.104 g/(m2·h) respectively.