The process of in-mold oxidation of cast aluminum alloy was analyzed.A kind of special coating contained the CrO

3

oxidant was coated on the surface of a sand core prepared by triethylamine cold box core-making technique.The sand core prepared was assembled in the mold after being dried

which was reacted with the aluminum alloy melt entried the mold to increase greatly the oxidized layer on the aluminum alloy surface.The results reveal that the processing results can be affected obviously by the content of oxidant

content of refractory aggregate and the particle size of refractory aggregate.With the200mesh SiO

2

powder as refractory aggregate

an optimum effects can be obtained when the special coating is composed of 105portions SiO

2

30portions oxidant

6portions bentonite clay

0.4portions CMC and 6portions mixed salts.The uniform oxidized layer with the thickness about 3!m can be observed.The corrosion resistance of samples in 3.5%NaCl solution was tested using electrochemical impedance method.It is found that the corrosion resistance of the samples after in-mold oxidization treatment is improved greatly.