Reclamation Information Sharing Environment (RISE)

The Bureau of Reclamation investigated zinc anode passivation in freshwater environments to improve galvanic anode cathodic protection systems. While zinc anodes offer advantages over magnesium, they are prone to passivation—a process where a non-conductive oxide layer inhibits corrosion protection. This study evaluated ultra-pure zinc electrodes in various natural and synthetic water samples using open circuit potential (OCP) and potentiodynamic scan (PDS) methods. Key water quality parameters and ionic compositions were analyzed to identify predictors of passivation. Results showed that higher levels of alkalinity, conductivity, potassium, and nitrate significantly increased the likelihood of passivation. Although no single factor was solely responsible, these constituents demonstrated strong statistical associations. Methodological refinements improved test reliability, with PDS at a 5.0 mV/s scan rate proving most effective. However, data limitations hindered robust multivariate modeling. Findings underscore the importance of site-specific water chemistry analysis when deploying zinc anodes and support the combined use of OCP and PDS methods for future evaluations.