Correlation between galvanic corrosion and electronic work function of al alloy surfaces

Abstract

Al alloys contain some secondary phases to improve their properties. These secondary phases have different potentials to the Al matrix, which greatly affect the localized corrosion of Al alloys. In order to reveal the physical nature of Al alloy corrosion, we use the first- principles method based upon density functional theory to calculate the work function of the main secondary phases (Al2Cu, Al3Ti, and Al7Cu2Fe). The difficulty of electrons escaping from various crystal planes was analyzed, and the potential difference between the secondary phases and Al matrix was obtained. We find that different crystal planes exposed to the outmost layer significantly impacted on the potential difference. Different atomic types at the outmost layer play different roles in Al alloy corrosion, even for the same crystal surface. The causes of galvanic corrosion were thus revealed. © Editorial office of Acta Physico-Chimica Sinica.