Characterization on Early Atmospheric Corrosion of Aluminium in Hongyanhe Nuclear Power Plant

Objective To study the characterization of early corrosion products of aluminium exposed to the atmosphere in the Hongyanhe nuclear power plant. Methods The samples were prepared and exposed to the atmosphere in Hongyanhe nuclear power plant according to the GB/T6464–1997. The corrosion products on the samples tested at 6 months and 10 months were observed and analyzed by means of SEM, XRD and FTIR techniques. Results There were corrosion pits and corrosion products and aggradations on the surface of the samples exposed for 6 and 10 months. The corrosion products were mainly Al2O3, AlOOH and aluminium salts containing chlorine and sulphur. The products were loosened with cracks on the upper and lower surfaces and pits near to each other were connected. The corrosion pits became larger and deeper over testing time, and the depth on the earthward (downward) surface reached up to hundreds of microns. Conclusion Corrosion of aluminium in the atmosphere in the Hongheyan nuclear power plant was mainly characterized by corrosion pits which was severer than in the normal atmosphere and the corrosion on the earthward surface was severer than on the upward surface. The synergic effect of SO2 and Cl played an important role in promoting corrosion process of aluminium.