Corrosion of Galvanized Hot Water Storage Tanks^★

In the following discussion of galvanized hot water storage tanks, it is assumed that all corrosion is electrochemical under the conditions existing in a hot water system. Electrolytic corrosion in water is the result of two simultaneous reactions: the solution of the metal in the form of metal ions at the anode, and the liberation of an equivalent amount of hydrogen by reduction of hydrogen ions at the cathode; These reactions involve the flow of electrons from the anode to the cathode through the metal. The solution of the metal at the anode results in a film of solution which is relatively concentrated with respect to the metal ion ; and increasing ionic concentration of the film causes the anode to become more electropositive, that is, its tendency to go into solution becomes less. At the cathode, liberated hydrogen acts as a hydrogen electrode, and the hydrogen ion concentration in...