Corrosion theory and the various electrochemical reactions that occur when iron corrodes in aerated cooling tower water are discussed. Corrosion inhibition mechanisms are presented along with an historical review of past and present inhibitor treatment programs.The "Practical Applications" section addresses issues facing the HVAC industry with respect to water treatment. These include the use of less skilled manpower, greater customer reliance on chemicals and equipment manufacturers, and the need for close control of water treatment parameters. Detailed discussion is presented on four major control areas: concentration control, chemical feed, pH control, and microbiological control. A bibliography with 25 references is provided for those interested in further detail.Units: I-P