Electrochemical Study On Performance Of Anodic Film Formed On Magnesium Alloy Az31

Magnesium alloy is known as the 21st century "green engineering materials", Because of its unmatched by other structural metals good characteristics, it is widely used in automotive, aerospace and telecommunications manufacturing industry. But since poor corrosion resistances of magnesium alloys restrict the further expansion of applications of magnesium alloys. The anodic oxidation is one of the most promising surface treatment technologies.In this paper, we have studied the parameters of anodic oxidation of magnesium alloy AZ31, and optimized anodic oxidation process. The growth process of anodic film was studied by SEM and AC impedance techniques. The corrosion process of magnesium alloy AZ31 and its anodic film were studied by electrochemical noise technique. The results show that:1. Oxidation time and current density has a positive influence on the formation of oxide film. The greater the parameter value, the easier the formation of oxide film, but when the value is too large, it will cause oxide film rough, corrosion resistance worse. Temperature has a negative influence on the formation of oxide film. The higher temperature, the more difficult the formation of oxide film, when the temperature exceeds 50℃, the anodic oxidation cannot proceed.2. Optimization parameters: oxidation time is 20min, the current density is 10mA/cm~2, and oxidation temperature is 20℃.3. When Immersed in the electrolyte, the sample surface will quickly form oxide film. And oxide film is a two-tier structure.The growth of the dense layer and porous layer is not synchronous, it is dynamic changes, and the two layers can be transformed into each other.4. Corrosion of magnesium alloy AZ31 first horizontal expansion, when the corrosion around the specimen, vertical expansion is begun. Alternating horizontal and vertical development. The corrosion process of the anodic film can be divided into three stages, stage of oxide film corrosive intrusion, corrosion and corrosion initiation stage of development intensified stage, the intrusion of corrosive media, corrosion initiation and propagation, increased corrosion.