| A number of magnesium alloy show promise as engine materials.However, a critical issue for the automotive industry is corrosion of the engineblock by the coolant and this could limit the use of magnesium engine blocks.At present, the main methods of corrosion protection of magnesium alloy werephosphating and inhibitors which was researched in this article.The basic phosphate solutions and processing parameters was determinedby orthogonal design experiment．The influence of the processing prametersand sodium molybdate as additive to the surface morphology, elementscomposition, and corrosion resistance of zinc phosphate coatings onmagnesium alloy AZ91D were studied．The properties of the coatings wereinvestigated by potentiodynamic polarization curves, electrochemicalimpedance spectroscopy(EIS)，scanning electron microscopy(SEM)，energydispersive spectroscopy(EDS) and so on． The results shows that: thephosphating pH, phosphating time and phosphating temperature have greatinfluence on the corrosion resistance of the zinc phosphating film. Sodiummolybdate changed the chemical composite of the phosphating film, improved the corrosion resistance of the zinc phosphating film.The composition of the inhibitor was determined with orthogonal designexperiment. The weight-loss experiment shows that the inhibition effect wasthe best excellent and up to94%when the mass fraction of the inhibitor was2%in50%ethylene glycol. The electrochemical performance and inhibitionmechanism of the composite inhibitor were studied by the dynamic potentialscan polarization curve, EIS and SEM analysis. The composite inhibitorcontrolled the anode reaction of corrosion process, could be consided as apassivation corrosion inhibitor. |
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