Preparation And Property Of Ceramic Coating On Cast Aluminum Alloy ZL102by Micro-Arc Oxidation

The ceramic coatings are prepared in the composite electrolyte ofsodium silicate, tungsten, boric acid, sodium metaaluminate, and EDTA(Ethylene Diamine Tetra acetic Acid) by micro arc oxidation method onthe ZL102casting aluminum alloy. The influences of the power mode, thecurrent density, micro-arc oxidation time on the performances of theceramic coating on the ZL102casting aluminum alloy were studied. Themorphology of the ceramic coatings was observed with scanning electronmicroscopy (SEM), the elements were analyzed by the EDS, the phasecomposition were analyzed by using the X-ray diffraction, and thecorrosion resistance was analyzed in the salt water and the acid solutionby using the electrochemical method.The experimental results show that: (1) The ceramic layers prepared by AC power have fewer holes, andthe surface roughness improved significantly, the corrosion resistance tosalt water and acid solution is better than those prepared by pulse power.The main elements of ceramic coating prepared by AC power are Al, Si,Na, W and O, but those prepared by pulse power are Al, Si, Na and W.The ceramic coating is mainly composed of Al, Si, and a small amount ofAl2O3.(2) The amount and the size of surface holes of the ceramic coatingsget reduced, and the particulate matters of the surface graduallydisappeared with the increase of current density and oxidation time.(3) Within the experimental range of current density, the corrosionresistance of the ceramic layer prepared by AC power increase both in thesalt water and the acid solution. Within the experimental range ofoxidation time, the corrosion resistance to salt water of layers getsimproved as the growth of the oxidation time until20minutes, then dropsas time goes by. But the corrosion resistance to acid solution becomes better as time goes on.(4) Within the experimental range of current density, the corrosionresistance to salt water of the ceramic layer prepared by pulse power isimproved with the increase of current density until0.26A/cm2, thenbecomes worse gradually. But the corrosion resistance to acid solutionbecomes better as the increase of current density.Within the experimental range of oxidation time, the corrosionresistance to salt water of layers gets improved as the growth of theoxidation time. But the corrosion resistance to acid solution firstly drops,then slowly increases as time goes by. When the oxidation time is10minutes, the corrosion resistance to acid solution is the best.