Al–Si合金ろう材の電気化学的性質に及ぼすCuとZn添加の影響

Abstract

Electrochemical measurements as well as immersion corrosion tests were carried out in order to investigate the effect of Cu and Zn content in the filler on localized corrosion characteristics and corrosion rate of the filler, and on pitting corrosion resistance of Al–Mn brazing sheet. Both Cu and Zn segregated at eutectic α–phase of filler after brazing. Selective dissolution of eutectic α-phase occurred not only in Al–Si alloy filler but also in Al–Si–Zn and Al–Si–Cu alloys after brazing. In Al–9%Si–2%Zn alloy fillers containing more than 0.1%Cu, both inner primary α and eutectic α–phase of filler dissolved and the outer primary α undissolved. Dissolution characteristics of filler were closely related to the pitting potential difference between the phases depending on solid solubility of Si, Cu and Zn. Brazing sheet clad with the Zn containing filler can be pitting corrosion resistant, because corrosion rate of filler was not so high and the filler was effective as sacrificial anode for the core.