Computer Simulation Of Galvanic Corrosion

With the development of materials science and technology,more and more materials are widely mixed used in engineering,therefore galvanic corrosion becomes an important issue to consider.This article has studied the effect of ? phase on micro-galvanic corrosion of magnesium alloys from the microscopic view and the effect of the geometry factors on complex galvanic corrosion from the macroscopic view and valuated the effect of galvanic corrosion proof of some design plans combining a engineering example for protecting a magnesium shell from galvanic corrosion via FEM software Comsol.The main content of this paper is as following:(1)A model for micro-galvanic corrosion of magnesium alloy is established through proper simplification,and the effect of beta phase size on galvanic corrosion of magnesium alloy was studied,to obtain distribution of surface potential and current density.Simulation results show that corrosion rate of alpha phase is the largest at the intersection of alpha and beta phase,and that as the distance from the junction increases the corrosion rate of alpha phase decreases.As the beta phase dispersion degree increases,the average current density of alpha phase increases gradually,the peak current density decreases,and the total current increases gradually,but there is little change on the whole.The difference between maximum current density and the minimum current density of alpha phase gradually decreases,and it tends to become the form of uniform corrosion.(2)The effect of complex galvanic geometry size and configuration on potential distribution and current density distribution was simulated by computer,and the simulation is verified by the galvanic current measurement test.Results show that no matter in what kind of configuration,when ratio of Al is constant,with the increase of ratio of Fe,the corrosion rate of Al gradually reduced.when ratio of Fe is constant,with the increase of ratio of Cu,corrosion rate of A1 gradually increased,and when ratio of Cu is constant,with the increase of ratio of Al,corrosion rate of A1 gradually reduced.Both measured and calculated value has shown that the configuration effect on galvanic corrosion trend is consistent,and under the condition of different configuration of the same composition point,the order of galvanic corrosion rate of Al from large to small is as following:Al in the middle>Cu in the middle>Fe in the middle.(3)Through the establishment of complex galvanic model,the effect of the coating on the current density distribution has been studied and a good galvanic corrosion protection scheme has been selected.Results show that no matter what kind of complex galvanic couple simulated,at the junction between Mg and A1 and nearby,the corrosion rate of Mg is the largest,and away from the junction the corrosion rate decreases.The corrosion rate of Mg reduces about 10000 times when A1 bolt is being used which both have the coatings and the protective effect is best in accord with the neutral salt spray test results.