Study On Corrosion Resistance Of Micro Arc Oxidation Ceramic Coating For Marine Aluminum Alloy

Aluminum has be used as the material of the piston which is the core component of the ship engine because aluminum alloy has the characteristics of small density,good thermal conductivity,high strength,stable chemical properties and so on.The piston is subjected to high temperature,high pressure and the wash by the high temperature gas.It's necessary to strengthen the surface treatment of aluminum because of the higher requirement of the corrosion resistance.Micro arc oxidation can be used to prepare a ceramic layer with corrosion resistance on the surface of aluminum alloy.The ceramic layer could have some special properties if the micro nano particles have been added into the electrolyte.The method of controlling variables has been used to study the effect of voltage,frequency and duty cycle supplied by the dual pulse power on the corrosion resistance of ceramic layer.The corrosion current density of the ceramic layer was calculated according to the polarization curves of ceramic layers.Scanning electron microscopy was used to observe the surface morphology and cross section morphology of the ceramic layer.The micro nano particles of serpentine,silicon carbide and molybdenum were added into the micro arc oxidation electrolyte at different concentrations to investigate the influence of micro nano particles on the corrosion resistance of ceramic coatings.Research shows that the parameters of micro arc oxidation power and the micro nano particles added into the electrolyte have effect on the formation of ceramic layers,their roles have changed the thickness and surface morphology of ceramic layer,affected the corrosion resistance of ceramic coatings.When the forward voltage is 420V,the negative is 120V,the thickness of the film is the best and the surface topography is good,the corrosion resistance is best.With the increase of frequency the thickness of the dense layer of the ceramic layer decreases,but the surface topography of the film is better.The prepared ceramic layer has best corrosion resistance.The increase of duty ratio makes the film thickness change step by step,but it has little influence on the corrosion resistance of the material.With the increase of serpentine concentration in the electrolyte,the thickness of ceramic layer is reduced,but the morphology of the ceramic layer becomes better when the corrosion resistance of the ceramic layer of serpentine concentration is 5g/L the best preparation;adding MoS2 particles changed the micro arc oxidation ceramic layer thickness,but the influence on corrosion resistance of materials is smaller;smaller concentration on silicon carbide effect of surface morphology of ceramic layer of silicon carbide ceramic layer,when the concentration of 2g/L prepared by the thick test showed that the corrosion resistance of ceramic layer the concentration of the best.