Most hulls of the ships are protected with paintings, sacrificial anode, and impressed current cathodic protection methods against corrosion problems. However, these conventional methods are not very effective because the rudder of ships stern are exposed to very severe corrosive environment such as tides, speeds of ships, cavitations and erosion corrosion. The environmental factors such as cavitation and corrosion will cause damage for materials with the shock wave by the creation and destruction of bubble. To solve these problems, the cavitation and electrochemical experiments are executed for thermal spray coating with Al−Zn alloy wire material. Thereafter, and sealed specimens with F−Si sealer on Al−Zn alloy coated specimen are executed to improve electrochemical and anti-cavitation characteristics in sea water. The application of fluorine silicon sealing after spray coating of 15%Al−85%Zn seems to be appropriate not only in static environment but also in dynamic environment.

Thermal spray coatingpresents a sacrificial-anode cathodic protection method since differences between the potentials of materials are employed. If a base metal is exposed to seawater, due to defect in the thermal spray coating, the metal is protected by the sacrificial anodic characteristics of the coating layer because micro-cells formed by the base metal and the thermal spray coating act as cathodes and anodes, respectively. The coating thickness has little effect on the surface morphology of the coating. However, the electrochemical properties with the increasing of coaBased on the excellent properties of nano coating, the preparation process of nano YSZ thermal spraying powder was studied. After spray drying, the fluidity, bulk density and microstructure of the aggregates were measured and analyzed by Holzer leak method and electron scanning microscope respectively. It is found that the higher the solid content, the better the fluidity and bulk density of the powder, but the higher the solid content will affect the granulation effect; in the case of a certain solid content, the better the fluidity of the agglomerated powder is after the slurry with moderate binder content is granulating. In order to obtain better agglomerate powder, the reasonable follow-up treatment method is plasma densification under the condition of 300A current and 40V voltage.ting thickness present good results.

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