Electrochemical Behavior of Nickel Brazing Filler Metal BNi-5 in NaCl Solution at High Temperature

摘要

Electrochemical measurements of SUS316L and BNi-5 were carried out to investigate the corrosion resistance of the portion brazed with nickel brazing filler metals in a heat exchanger made of austenitic stainless steel. The corrosion potentials and galvanic currents of SUS316L and BNi-5 were measured in 0.06 mol/L sodium chloride and sodium sulfate solution at room temperature and at 80°C. The corrosion potential of BNi-5 in NaCl solution at 80°C is lower than that in NaCl solution at room temperature, while the corrosion potential of SUS316L in NaCl solution at 80°C is almost the same as that in NaCl solution at room temperature. The corrosion potential of SUS316L was nobler than that of BNi-5 in NaCl solution. The potential difference between SUS316L and BNi-5 in NaCl solution at 80°C was up to about 0.4 V. The galvanic current between SUS316L and BNi-5 in NaCl solution at room temperature was almost 0 μA/cm~2, while the galvanic current at 80°C was up to about 0.2 uA/cm2. We found that galvanic corrosion on the couple between BNi-5 and SUS316L may be induced in a solution containing chloride ion at high temperature.