On Corrosion Mechanism of Gold-plated 7-3 Brass by NaCl aq. Solution

Abstract

In the earliest stage within 72hr. at 70-80°C-of corrosion of gold-plated 7-3 brass by 5% NaCl aq. solution, ZnO alone was observed as corrosion product on the surface, and any other corrosion products such as zinc basic chloride, zinc hydroxide, cuprous oxide, copper basic chloride and cuprous chloride could not be detected. In order to verify the mechanism of corrosion, matrix Cu, Zn and 7-3 brass and gold-plated specimen were dipped in NaCl aq. solution, and then by using X-ray back reflection and electron transmission diffraction method these were identified with standard X-ray diffraction data. From the results, it was concluded that ZnO was preferentially formed on gold-plated 7-3 brass as corrosion product due to galvanic reaction between gold and zinc, and that corrosion seemed to be accelerated, in general, by contact with second metal.