At elevated temperatures most aluminum alloys in water suffer severe penetrating attack, resulting in their relatively rapid destruction. This penetrating attack is explained in terms of mechanical damage as a result of diffusion of corrosion-product hydrogen into the metal.
It is prevented by adding to the water cations which are reduced on the aluminum to form deposits of low hydrogen overvoltage metals. It is also prevented in untreated water by using aluminum alloyed with the same metals. Alloying metals observed to be beneficial are nickel, copper, cobalt, iron and platinum, with nickel probably the most effective.
There has been developed an alloy, containing approximately 1 percent nickel in 1100 aluminum, which appears to be completely safe against the penetrating attack up to 350 C. It is easy to make and is workable. It probably can be used, from a corrosion-resistant point of view, wherever its normal reaction rate with water or a solution is tolerable. Penetration rates in static distilled water range from approximately 0.5 mg/dm2-day at 150 C to 18 mdd at 350 C (0.3 to 9 mils per year). They are higher where there is significant flow velocity of water past metal. 6.4.2
