Fossil, Specifying, galvanized carbon steel tubing in an air-cooled powerplant condenser is a compromise among several factors. Some of these compromises are: - Cost ( galvanized CS is inexpensive) - HT Coeffiecient ( CS is better than SS) - Availability - Structural support (SS tubes are typically thinner, require shorter spans) For power plants, these condensers are massive...they do not perform well in hot weather....... and are only typically used in arid locations where there is little or no surface water. You should also understand that for most climates, an extended surface ( finned tube) design is the only reasonable soultion to the problem of transfering heat between barely warm water and ambient air. Putting fins on large diameter SS tubes is not commonly done. Would the finned SS tubes offer longer life ??? Most likely..... Would they be cheap.......nope.... My opinion only MJC