Effects of Cu content in the core, Zn in the filler, and sheet thickness on the corrosion resistance of a brazing sheet

Abstract

The effects of Cu content in the core and Zn in the filler of a brazing sheet of 0.2 mm thickness as well as those of 0.3 and 0.5 mm thicknesses has been investigated. The corrosion form changed from pitting to general corrosion by adding more than 0.2% Cu to the core in the sheets of 0.3 and 0.5 mm thickness, while pitting corrosion occurred in all the 0.2 mm 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 0.2 mm 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 the gradual potential slope formed in the core due to Zn diffusion during brazing.