Anti-Corrosion Coating Of AZ91D Magnesium Alloy And The Study Of The Coating's Properties

Magnesium alloy is the lightest metallic structural material on earth,it has many good properties such as high strength,high thermal conductivity and dimensional stability,good machinability and electromagnetic shielding characteristics,so magnesium alloy is widely used in many applications. However,magnesium alloy has a high chemical reactivity which caused magnesium alloy corrodes easily,so it is necessary to take some effective measures to improve the corrosion resistance of the material.Currently,there are a lot of surface treatment techniques available for magnesium alloy. Unfortunately,these surface treatment techniques all contains diverse disadvantages,these is not a single coating technique which can protect the magnesium alloy from corroding under tough environment.In this paper,the principle of cathodic protection as a starting point, developed a zinc-rich coating similar to magnesium-rich coating.Through the incorporation of two different particle size(20 micron and 38 microns),made of different magnesium content of magnesium-rich coating,Brush in the AZ91D magnesium alloy matrix.The test results show that the coating:1.Coating with excellent mechanical properties:Adhesion to level 1,the impact strength more than 50kg·cm.2.Resistant to salt spray test showed that compared with epoxy varnish, the coating has improved corrosion resistance,20-micron-level magnesium content is 50%better corrosion resistance,resistant to salt spray test time is about epoxy varnish 3 times.3.The particle size of magnesium corrosion resistance coating has improved,20-micron-level effect of magnesium is slightly better than 38 micron powder;and magnesium content of the two,50%are the most corrosion resistance.4.Through immersion EIS testing,studies the coating failure process. Coating failure is divided into three phases:Infiltration mainly in the course of the early immersion,the internal dissolution and swelling due to the initiation of micro-cracks and porous in the medium-term immersion,emergence of the bubble in the late immersion.