Even though several stainless steels and a few nickel based alloys have shown promise and are used in marine environments, under very severe crevice corrosion conditions, most of these have suffered from localized crevice attack. The search for alloys that are essentially immune to crevice corrosion attack in marine environment led the industry to
increase the alloy content of nickel based alloys primarily in chromium and molybdenum. One such alloy, alloy 59 (UNS N06059) having a typical chemical composition of 59% nickel, 23% chromium, 16% molybdenum and iron levels of less than 1%, appears to have fulfilled this need. Extensive laboratory and field tests by various companies and corrosion laboratories in USA, U.K., Norway, France and the U.S. Navy have shown this alloy to be essentially immune to crevice corrosion attack. Based on the excellent crevice corrosion resistance of alloy 59, the U.S. Navy has selected this alloy for testing a prototype component in
a butterfly valve and is conducting further tests for overlay welding application as a superior alternative to alloy 625 and C-276. This paper presents a brief description of this alloy's development, its physical metallurgical characteristics and localized corrosion data from various test programs. Other companies are also evaluating this alloy for use in a weld overlay application on off-shore platforms.
Keywords: Marine corrosion, seawater corrosion,, alloy 59, UNS N06059, crevice corrosion, localized corrosion, applications.