| Because of their small density,high strength advantages,magnesium alloys have broad application prospects in the field of automotive and aerospace.However,poor corrosion resistance of magnesium alloys greatly restricted their development.Then,improvement the corrosion resistance of magnesium alloys is of great significance to the application promotion for magnesium alloys.Previous studies suggested that Mg-rich epoxy coatings can offer cathodic protection to magnesium alloys to some extent.However,the cathodic protection time of Mg particles was relatively short due to the high reactivity of Mg particles.Meanwhile,the coating lifetime was shortened by the loose structure of corrosion products for magnesium particles.In order to reduce the reactivity of Mg particles and improve the protective performance of Mg-rich coating on AZ91D magnesium alloy,we choose stannate to pretreat Mg particels.The effects of stannate pretreatment time for Mg particles on the morphology and composition of Mg particles and the corrosion resistance of Mg-rich coating on AZ91D alloy were investigated.Also,the influence of the stannate pretreated Mg particles content on the coating protective performance was studied.The results showed that:?1?After pretreated in stannate solution,a conversion coating layer formed on the surface of Mg particles.The composition of the film contains Mg,O and Sn,which was identified as MgSnO3 and Mg?OH?2.With prolonging of the processing time,the conversion film become thick,the corrosion resistance got good and the pure magnesium was reduced.?2?Coating contains magnesium powder which pretreatments for different time have certain protective effect,however,the protect effect will be decreased if the processing time is too short or too long;the sample coating which contains 40 min,50 min,60 min pretreatment magnesium soon separation bubble or coating and the magnesium substrate,because of its large coating porosity.The coating contains magnesium powder which pretreatment for 10 min and 20 min have a obviously improve in protective effect.?3?The stannate pretreated magnesium-rich coating can provide a degree of cathodic protection to magnesium alloy substrate,at the same time,coating contains magnesium powders which are pretreated for different time have a protective effect to breakage magnesium alloy substrate.In all the samples,the coating contains magnesium powder which is pretreated for 20 min has the best quality.?4?magnesium stannate for pretreatment can significantly improve the magnesium rich coating on the coating damage the protective performance of magnesium alloy matrix;high content of magnesium stannate preprocessing,coating protective performance is good.?5?the coating of magnesium stannate for pretreatment performance is more stable,magnesium powder reactivity and reaction activity area with the immersion time of extend switch is relatively slow,thus extending the action time of magnesium powder,the service life of the coating is prolonged;containing 60%stannate pre coating of magnesium to magnesium alloy matrix protective effect for a long time,coating performance is more stable. |
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