Effects of Cu Content in Core, Zn in Filler and Sheet Thickness on Corrosion Resistance of Brazing Sheet

Abstract

Effect of Cu content in core and Zn in filler of the brazing sheet of 0.2mm thickness as those of 0.3mm and 0.5mm has been investigated. Corrosion form changed from pitting to general corrosion by adding more than 0.2%Cu to core in the sheets of 0.3mm and 0.5mm thickness, while pitting corrosion occurred in all the 0.2mm thickness sheets even containing Cu after 20 days SWAAT. On the other hand, residual life after corrosion was greatly improved by suppression of localized corrosion even in the sheets of 0.2mm thickness clad with filler containing more than 1%Zn, independently of Cu content in the core. The suppression of localized corrosion was caused both by higher potential difference between filler and core, and by gradual potential slope formed in the core due to Zn diffusion during brazing.