Corrosion and metal release in drinking water systems are affected by the chemistry of ambient water (e.g., pH, concentrations of carbonate and other ions), stagnation/flow transitions associated with diurnal and seasonal changes of water consumption as well as the introduction of alternative water sources, for instance desalinated water. Control of metal release in drinking water is mandated by the EPA within the Lead and Copper Rule (LCR). The current LCR paradigm of copper and lead monitoring is based on measurements of metal concentrations at the end of a predetermined stagnation time (e.g., > 6 hours). While this approach is suitable for the general evaluation of LCR compliance, it does not provide any information concerning metal release in short-term stagnation episodes nor does it allow evaluating effects of short-term changes of water chemistry.

The goal of this study was to address these deficiencies based on the quantitation of transient changes of open circuit corrosion potentials (E_corr) of metal surfaces during stagnation/flow episodes and examining relationships between such changes and attendant metal release at varying water chemistries. Experimental data demonstrate that E_corr transients for copper, lead and iron are characterized by several consistently present features. Theoretical interpretation shows that the E_corr transients are associated with the concurrent processes of release of metal solutes and consumption of oxidants (dissolved oxygen, chlorine species). The former process is dominant in the case of copper or lead while the latter effect is more significant for higher corrosion rates typical for iron. Further modeling shows the presence of the phase of rapid quasi-exponential consumption of the oxidants at the surface followed by a slower phase associated with the development of diffusion controlled fluxes.

These results show that the monitoring of E_corr transients allows quantitating corrosion and metal release rates in conditions characteristic for drinking water systems, notably when other methods either do not provide relevant data or cannot be deployed.