Numerical And Experimental Study On Galvanic Corrosion Of Bolts In Magnesium Alloy Wheel

Magnesium alloys has become a hot topic because of its excellent physical properties in recent years in the field of lightweight of automobile.With the successful application of aluminum alloy wheels,some researchers were inspired to start an evolving field of magnesium alloy wheels.However,poor corrosion resistance of magnesium alloy has become a major constraint impeding the wider use of magnesium alloy wheels.Especially the galvanic corrosion of magnesium alloy and dissimilar metals.In this paper,galvanic corrosion of bolts in magnesium alloy wheels is studied.The main contents are as follows:Aiming at the problem of galvanic corrosion of magnesium alloy in the automotive industry.The model of bolts in wheel is built and the governing equations are derived to analyze galvanic corrosion.In combination with a moving mesh technique,the galvanic corrosion behavior of bolts in hub in a sodium chloride solution was investigated by finite element method.And the influence of the radius and depth of the bolt hole is analyzed.A simplified test specimen of galvanic corrosion of bolts in magnesium alloy wheels is designed.Machining the holes and bolt holes in the AE44 magnesium alloy blocks,and tightening 45# steel bolts with magnesium alloy block by nuts.The full immersion test of assembly test specimen in the NaCl solution is done.There are two groups of tests in all.Firstly,the different corrosion morphology of Mg alloys surface of the blank samples without steel bolts and galvanic corrosion samples are analyzed.Secondly,the different corrosion morphology of Mg alloys surface with different immersion time are analyzed.The validity of numerical simulation is checked by comparing the immersion experimental results in the salt solution and the simulation results of the three-dimensional model.The simulation model of galvanic corrosion in atmospheric environment of steel fastening bolt in magnesium alloy wheels is established by improving the galvanic corrosion model in the salt solution.The galvanic corrosion behavior of steel fastening bolt in magnesium alloy wheels in atmospheric environment is simulated and analyzed.The effects of relative humidity of atmosphere and salt deposition density on Mg alloy surface on galvanic corrosion are discussed.