Effects of Passivation Treatment on Corrosion Behavior of Al-B₄C Composites

Passivation treatment was conducted on the surfaces of Al-B₄C composites by triethanolamine solution. The effects of passivation treatment on the corrosion behavior of the Al-B₄C composite were investigated through electrichemical test and immersion corrosion test. The results show that the passivation treatment made a duplex-layer oxide film form on the surface of Al-B₄C composite. The oxide film consisted of a continuous amorphous inner layer in a thickness of about 2.5 μm and an outer layer containing triclinic and monoclinic Al(OH)₃ in a thickness less than 1 μm. The passivated Al-B₄C composite had a large polarization resistance and showed good corrosion resistance. After 1 000 hours of corrosion immersion in boric acid solution at 40℃, the weight-increase after corrosion and metal ion dissolution for the passivated Al-B₄C composite were significantly lower than those for the unpassivated Al-B₄C composite, which indicated that the oxide film forming during passivation treatment could increase the corrosion resistance of the Al-B₄C composite.