The cost and reliability of modern steam power systems depends on our ability to predict material performance in the boiler system environment. A major concern to the Navy in shipboard applications is the large surface area of numerous condensers which must resist deterioration over a wide variety of operating conditions. Since much of this area is inaccessible, many field problems have not been characterized; defective tubes are often plugged or replaced without analysis of the tube or condenser environment to determine a remedy. Copper based alloys have traditionally been used for their excellent corrosion resistance and antifouling properties in saltwater. These alloys however have been plagued with steamside ammonia related corrosion, a particularly difficult problem to detect and predict.(1) Ammonia is a common ingredient in most boiler systems, either as a direct additive for pH control, or a by-product from decomposition of additives, impurities, and organic coatings. In the steam condenser air removal system, ammonia and other corrosive agents are concentrated by system recylcing and absorbed in stagnant condensate on the tube surface. Reduced tube corrosion in this area can be achieved by converting from brasses to copper-nickel alloys(2), and adopting improved water chemistry standards and control. Since these earlier efforts, the Navy has sought further improvements, and consequently initiated the experimental work reported in this paper to determine the performance of alternate tube materials under steam system conditions aggressive to Cu-Ni alloys.
