The protective role of hydrozincite during initial corrosion of a Cu40Zn alloy in chloride-containing laboratory atmosphere

Hydrozincite, Zn5(CO3)2(OH)6, was recently found to play a key role in reducing corrosion product flaking on Cu-Zn alloys. A fundamental study was undertaken to explore the underlying mechanisms, in particular why hydrozincite can suppress the interaction between chlorides and the alloy surface. Hydrozincite could be formed by exposure of Cu40Zn to air at 70% relative humidity and 1000 ppm of CO2 resulting in a surface of decreased wettability. Its presence reduces the initial spreading ability of NaCl-containing droplets and lowers the overall initial corrosion rate when the alloy is exposed to pre-deposited NaCl and wet/dry cycles.