Electrochemical Study about Grooving Corrosion on Copper Tube Near Brazing Part

Abstract

Brazing is the main method used to connect copper tubes in heat exchangers of air–conditioning and sanitary equipment, and leakage accidents have occurred due to grooving corrosion on the copper tube near the brazing parts. The corrosion progressed by the galvanic action, in which copper was the anode and brazing filler metal was the cathode. Here, we studied the effects of solution flow, solution conductivity, and types of ions on grooving corrosion on the copper tube near the brazing parts by electrochemical measurement of copper plate, copper tube and brazing filler metals. In the test, we used BCuP–2 and BCuP–3 as brazing filler metals. The results showed that the brazing filler metals and the carbon film on the inner surface of the copper tube affected corrosion potential in tap water. The corrosion current density increased with increasing conductivity on actual tube and BCuP–2. The effects of solution conductivity and types of ions on corrosion current density were greater for BCuP–3, and it was thought to be that silver contained in the brazing filler metal influenced the effect.