MDL Zincs Anodes prevent galvanic corrosion of boat parts and components below the waterline by setting up a dominant, positive current flow. The number of anodes and their location depend on the size and type of boat construction. Anodes are limited-life components, designed to sacrificially decompose. Never paint anodes. Reliance anodes are made from a high purity zinc with added catalysts to produce an "activated alloy", ensuring the anodes give one hundred percent of themselves to protect your boat from corrosion action. In order for an anode to work properly it must be free of unwanted impurities.