ABSTRACT
Nickel-based alloys used in marine environments are normally derived from the Ni-Cr-Mo or Ni-Cu alloying systems. High nickel content provides alloys with a tough, ductile crystal structure that can be used down to cryogenic temperatures without fear of embrittlement. Nickel-iron-chromium-molybdenum alloys also have very low general corrosion rates and are unaffected by flow rates as great as 40 m s-1. Potential forms of corrosion in nickel alloys used in marine environments are pitting, crevice corrosion, and stress corrosion cracking. Nickel maintains the austenitic-type structure so that high levels of molybdenum can be added while still maintaining a stable alloy. High-nickel alloys are noble and it is usually the alloy they are connected to that is likely to suffer from galvanic corrosion when area ratios are unfavourable. While nickel alloys can generally be welded without difficulty, design and selection of suitable filler metals for corrosive environments require careful consideration.
