Riser tube coating for cast aluminum alloy and using method thereof

A riser tube coating for a cast aluminum alloy, characterized by comprising a coating-riser tube contact layer material and a coating-aluminum liquid contact layer material, wherein the coating-riser tube contact layer material comprises ZrO2, Al2O3, ZnO and a binder, ZrO2 accounts for 70%-80%, Al2O3 accounts for 10%-15%, ZnO accounts for 10%-15%, and a weight ratio of the binder to the materials is 10:1;

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• the coating-aluminum liquid contact layer material is mainly ZrO2, Al2O3, ZnO and a binder, in the coating-aluminum liquid contact layer material, the ZrO2 accounts for 80%-90%, Al2O3 accounts for 5%-10%, ZnO accounts for 5%-10%, and a weight ratio of the binder to the materials is 15:1.