Effects of pH, chloride, bicarbonate, and phosphate on brass dezincification

摘要

Knowledge about the long-term effects of water constituents on brass dezincifica-tion is fairly limited, and important quantitative data such as weight loss and levels of zinc leaching were rarely collected in earlier research. The effects of hardness and alkalinity in dezincification are unclear because of various interpretations of the classic Turner diagram. In this research, experiments were conducted to elucidate the interplay between water chemistry and dezincification. The authors identified a critical pH range of 8 to 9 at which "meringue" dezincification is problematic and refined the interpretation of the Turner diagram by attributing beneficial effects to higher alkalinity rather than hardness (or temporary hardness). Chloride was found to increase dezincification propensity by increasing zinc solubility and galvanic current, whereas hardness had little to no effect on brass dezincification. That inhibi-tive effects of orthophosphate dissipated after about 100 days raises questions about the long-term efficacy of phosphate inhibitors in mitigating brass dezincification.