Study On The Micro-Galvanic Corrosion Behavior Of WE43 Alloy In NaCl And Na₂SO₄ Solutions

Magnesium and magnesium alloys are widely used in aerospace industry,hydrogen storage energy industry,biomedical engineering and digital 3C civil fields due to their excellent properties such as low density,high specific strength,high energy density and good biocompatibility.However,poor corrosion resistance and low absolute strength restrict the application of magnesium alloys in industrial production.The addition of rare earth elements to magnesium alloys is a common method to improve the properties of magnesium alloys.The cast WE43 rare earth magnesium alloy is an alloy with good heat resistance and stability.At present,the research focus is still on the heat resistance mechanical properties of the alloy.The research on the corrosion properties of the alloy is relatively few,especially the micro-galvanic corrosion behavior and corrosion resistance of the alloy under different corrosion conditions.Therefore,the study of corrosion mechanism of WE43 rare earth magnesium alloy is of great value for promoting the application of this alloy.Based on cast WE43 rare earth magnesium alloy as the research object,using X-ray diffraction（XRD）,optical microscope（OM）,scanning electron microscopy（SEM）and scanning kelvin probe force microscope test（SKPFM）and hydrogen evolution weightlessness and electrochemical testing device and method,system research the micro galvanic corrosion,corrosion resistance and electrochemical properties of cast WE43 rare earth magnesium alloy in Na Cl solution and Na₂SO₄ solution:（1）In the immersion experiments of Na Cl solution and Na₂SO₄ solution,the effect of second phase on the micro-galvanic corrosion of WE43 rare earth Mg alloy is completely opposite.In the micro-galvanic corrosion of Na₂SO₄ solution,the second phase of WE43 rare earth Mg alloy as the micro-anode phase is preferred to corrode.In the micro-galvanic corrosion of Na Cl solution,the second phase acts as the micro-cathodic phase to promote the corrosion of magnesium matrix.（2）The corrosion resistance of WE43 rare earth magnesium alloy in Na₂SO₄solution is worse than that in Na Cl solution,which is different from the traditional idea that chloride ion has stronger erosional power.By observing the cross section of the protective film,we found that the protective film formed by the WE43 rare earth magnesium alloy in the Na Cl solution distributed on the whole surface,complete and uniform;However,the protective film formed in Na₂SO₄ solution is relatively porous,especially the absence of protective film is obvious at the position above the second phase,which may be the direct reason for the poor corrosion resistance of WE43 rare earth magnesium alloy in Na₂SO₄ solution.The second phase dissolved easily in Na₂SO₄ solution and could not form protective film,which may be the root cause of the corrosion difference.