Corrosion of Aluminum-Nickel Type Alloys In High Temperature Aqueous Service

Aluminum can be made resistant to high temperature water by small alloying additions of Ni, Fe and Cu. In the presence of adequate concentrations of the cathodic second phase formed by these additions, the high temperature attack changes from grain boundary penetration and blistering to a more desirable uniform overall attack. The latter causes two films to be formed on the corroding surface, Film A growing outward from the original surface and Film B growing inward into the metal. Film A reaches a limiting thickness after 2-3 weeks at 300 C, but Film B continues to grow linearly with time. At this stage the corrosion rate is acceptably low (~∼ 1 × 10−³ inches/yr) but the corrosion film is 10-20 μ thick, relatively brittle and subject to severe, mechanical damage in water flowing at high linear velocities. Reactor radiation has an insignificant effect upon corrosion. Heat fluxes of the order of 10O watts/cm² also appear to have little, effect, though in this instance the effect may have been obscured by mechanical damage.

Extensive test data are reported on the corrosion resistance in high temperature water of three specially selected aluminum alloys. 4.6.5