Abstract: In a water injection well, in place of corrosion inhibitors, the internal surface of a lower section of the casing is protected from corrosion by one or more galvanic sacrificial anodes placed in the section of casing. The anodes are mounted on a metal member which is connected to or suspended from the tubing or a well packer. The metal member extends below a certain point in the well into the section of casing. The metal member may be a tail pipe or it may be a wireline retrievable member specially prepared for this purpose. Anodes made of an aluminum alloy are especially suited to this corrosion protection system.