With its considerable industrial benefit as an effluent coolant, seawater remains a corrosive environment to many structural materials. Problems related to localized corrosion, erosion/wear, and biofouling represent limitations to the use of many metallic materials. Cumbersome cathodic protection techniques, unanticipated maintenance costs, along with reliability of equipment, safety to personnel, and environmental concerns are leading to a wider use of higher performance nickel-based alloys in seawater services.
Over the years, the nickel-chromium-molybdenum/tungsten alloys have proven to be among the most reliable and cost-effective materials for aggressive seawater applications. Of these, INCONEL® 625 is considered acceptable and the HASTELLOY® “C-type” alloys (C, C-4, C-276, C-22®) are considered optimum.
HASTELLOY alloy shows unsurpassed resistance to corrosion in seawater atmosphere. Exposed at Kure Beach, N. C., since 1942, HASTELLOY C sample continues to keep its original surface finish while the rest of the test allots have disintegrated long ago.
The high nickel alloys offer excellent resistance to localized corrosive attack (pitting, crevice corrosion), when compared to stainless steels.