The copper and silver ionization system is one of the water sanitation treatments. Effective ionization occurs if the
content of copper ions in solution is 0.2-0.4 mg/L and that of silver ions is 0.02-0.04 mg/L. An excess of copper
and silver ions can react with other metal surfaces, triggering a deposition reaction, allowing the formation of
deposits of more noble metals, and then promoting a localized corrosion phenomenon due to galvanic coupling.
In the present paper, two case histories will be presented: one related to a legionella sanitizing plant system of a
hospital; the second related to a system of water purification of a vessel on a boat. In both cases, working
conditions are illustrated, corrosion morphology is described, focusing on the presence of copper and silver
deposits, and the cause of corrosion is presented, estimating a reliable corrosion rate
