Effect of alloying additions on sea water corrosion resistance of iron--aluminum base alloys

Wrought sheet corrosion specimens of varying aluminum (6 to 16%), molybdenum (to 8%), chromium (to 2%), copper (to 3%) and nickel (to 3%) were exposed to ambient and boiling sea water. Corrosion weight losses were measured and compared to AISI-SAE 1008 steel and Cupro-nickel (CDA 706) as baseline materials. The more promising alloys were rotated in ambient and 190 F (90 C) sea water at velocities up to 15 ft/sec (4.58 m/sec) to evaluate resistance to erosion-corrosion. A minimum of 10% aluminum was found necessary to maintain a protective oxide film. Under certain conditions, molybdenum additions up to 4% reduced corrosion weight losses by an order of magnitude. Chromium, nickel, and copper additions were found to impart only slight improvement and, in certain cases, were detrimental to corrosion resistance. Weldments of copper-containing alloys were subject to selective corrosive attack, and those of low-aluminum (10%) content were found to be unsuitable in hot sea water.