Abstract
Corrosion of copper material in drinking water systems causes public health concerns and plumbing failures. This study investigated the early corrosion of new copper surfaces in situ using a novel technique: quartz crystal microbalance with dissipation (QCMD). The QCMD results showed that increasing the water pH from 6.5 to 9.0 and the addition of 6 mg/L orthophosphate at pH 6.5 and 9.0 slowed down the copper surface mass changes as indicated by the reduced changes in frequency (Δf5) at 51-89% and total copper release at 29-72%. The water pH 9.0 without orthophosphate was the most likely to induce localized corrosion relative to other conditions at pH 6.5 and pH 9.0 with orthophosphate. Based on the changes in dissipation values (ΔD5) from QCMD and the morphology, microstructure, and composition of the deposited copper corrosion byproducts, digital microscopy, field-emission scanning electron microscopy with energy dispersive spectroscopy, and X-ray photoelectron spectrometry analyses confirmed that the pH and orthophosphate inhibited copper corrosion with different mechanisms. QCMD provided sensitive, rapid, and continuous responses to mass and surface changes and can be useful for evaluating early water corrosivity to new copper.