Effect of 3 wt% Al Content and Rapid Solidification on the Erosion-corrosion Behavior of 92 wt% Cu and 5 wt% Ni Alloy in Seawater

Abstract

A 92 wt% Cu and 5wt% Ni alloy containing 3 wt% Al is subjected to a rapid solidification processing (RSP) using a rotating copper wheel (7.95 cm φ x 5.95 cm w) at 1420 r.p.m, which produces a thin specimen of 2 mm thickness. The specimens with dimensions of 10.8×15.02 mm2 are then exposed to water flow rate for 28 hours at 30°C and then the corrosion/erosion rates were computed in (g cm-2 h-1) using weight loss measurement method. The corrosion rate of the produced alloy under constant water flow rate tests decreases generally with time (1.5 - 28 h)  and showed only initially some short periods of accelerated oxidation (0.0 - 1.5 h). The obvious weight loss and corrosion rate versus exposure time relationships are rationalized in terms of film formation was hard and its breakdown mechanisms did not occur. The effective of Al2O3 in improving the corrosion/erosion resistance was provided through addition 3% Al to the binary 92% Cu-5% Ni alloy. Thus, a passivity, dense, adherent, and continuous Al2O3 film exists on the surface protecting bare alloy from further oxidation and causing the metal to be little deterioration Moreover, fine inner layer of Cu2O or CuO acts as a super resistance barrier to erosion-corrosion. The metallographic images were photographed using a metallurgical microscope at 1000X magnification to identify the influence of rapid solidification on the structure includes nucleation, grain size, grain growth and particles pushing.