| The magnesium alloys which are becoming an alternative to a new structuralmaterial in place of aluminum alloys and steel are used in the automotive, militaryproducts, metallurgy, digital products and so on in recent years. Due to the light weight,higher specific strength than aluminum alloys and steel, higher stiffness which is notonly no apparent different with aluminum alloys and steel, but also much better than thecarbon fiber reinforced plastic, better thermal fatigue and magnetic shielding resistancethan plastic and convenient recycling. Especially for the automotive industry. With therapid increase in the global economy, the demand for energy is increasing. Not only thedevelopment of new energy sources but also energy saving which requires lightweightautomotive components is considered to satisfy, including automotive wheel.But it limits the widely use of magnesium alloys in automobile wheel hub becauseof its poor corrosion resistance. To a certain extent, although more and more researcheson magnesium alloy surface coating had made progress, no one has research on thecorrosion resistance of magnesium alloy surface with cracks in the domestic and abroad.This paper will focus on the side of investigation.In the present work, preparing two kinds of coatings by micro-arc oxidation andelectrostatic spray on the surface of deformation AZ80. The investigation on thecorrosion resistance of the cracks being on or not on the two coatings by means ofMachu test, electrochemical test, saline soak, electrical resistivity measurements, saltfog test, etc. This investigation establishes a foundation for the application ofautomotive wheels. The main results are as follows:①After saline soaking the corrosion products generation on the MAO andelectrostatic spray coating on deformation AZ80alloy are less than the bare substrate, itshows that the two coatings can improve the corrosion resistance. But the electrostaticspray coating has worse water resistance than MAO coating, so it is easy to shell andpeel off after soaking for a certain time, at this time it has worse corrosion resistancethan the MAO coating.②After0.49J,0.98J,1.96J and3.92J impact energy shock, the corrosionresistance of the damaged MAO coating is worse than the intact one, the weakeningdegree is along with the increase of impact energy. Especially the impact energy isgreater than3.92J, the corrosion resistance decreases significantly which the impact crack local corrosion velocity approaching the bare substrate due to the dense layer isdamaged and the matrix form variables is very large. When control the total length andarea of crack, the corrosion speed of the coating of the minor scratches which are notreach to the matrix are not change with the change of the length of single scratch, andalso keep consistent with the intact coating. Contrarily, the corrosion speed of thescratches which are reach to matrix is much faster than the intact coating, and itincreases with the increase of the length of single scratch.③After0.49J,0.98J,1.96J and3.92J impact energy shock, the corrosionresistance of the damaged electrostatic spray coating is worse than the intact one, at thistime the impact part of the coating is easier to peel off along the direction of microcrack after soaking to make the corrosion speed accelerate which leads to decline thecorrosion resistance. When control the total length and area of crack, the corrosionspeed increases with the increase of the length of single scratch whether the scratchesreaches to matrix. But due to the water resistance is poor, the corrosion resistance ispoor no matter whether there is cracks on the coating. Totally, at this time, the corrosionresistance not all depends on the nature of the cracks but depends on the performance ofthe coating powder itself. |
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