The effects of surface chemical treatment on the corrosion behavior of an Al-B4C metal matrix composite in boric acid solutions at different temperatures

The effects of surface chemical treatment (ST), which is a combination of acid and alkaline cleaning to remove surface impurities, on the corrosion behavior of an Al-B4C metal matrix composite (MMC) in boric acid solutions at 40 ℃ and 90 ℃ were investigated. SEM and TEM analysis revealed duplex-layer surface scales, consisting an outer layer of blade-like strips and a continuous amorphous inner layer. The outer layers have similar thicknesses, while the impurity-containing samples (without ST) have thicker inner layers, in which the interfaces between the impurities and surrounding oxide scale were acted as fast inward diffusion channels of oxygen.