As a light engineering metal material, magnesium alloy has high specific
strength, specific stiffness, specific elastic modulus, and good castability and
cutting performance. Therefore, it is increasingly used in the fields of
automobiles, electronics, home appliances, communications, instrumentation, and
aerospace, and is known as the green engineering metal structural material of
the 21st century. However, magnesium alloys are extremely susceptible to
corrosion, which greatly limits their applications. Today China Die Casting
parts Factory will tell you, how does magnesium alloy prevent corrosion?
Magnesium Alloy Die Cast Part
Corrosion is the destruction of metals in the surrounding medium due to chemical, electrochemical, or physical dissolution. From an energy point of view, the tendency of metal corrosion can be judged by the amount of energy consumed to smelt the metal from the ore. As a structural material, magnesium alloys are prone to corrosion in the use environment, which greatly limits its practical application.
Main Forms of Magnesium Alloy Die Cast Part Corrosion
1. Galvanic corrosion and general corrosion
The high reactivity of magnesium makes it easy for magnesium to form corrosive cells with other phase structures and galvanic corrosion.
The local corrosion of magnesium alloy is mainly a little bit corroded and filiform. Magnesium is a naturally passivated metal. In a medium containing Cl-, the passivation film of magnesium or magnesium alloy is easily damaged and pitted, and it will also occur in neutral or alkaline salt solutions. Heavy metal contaminants can accelerate the pitting of magnesium alloys.
3.High temperature corrosion
Manufacturers of magnesium alloy die-casting remind that the oxide film on the surface of magnesium alloy has a protective effect in a long time under the dry oxygen of 450 ℃.
Under fatigue loading, the origin of microcracks in magnesium alloys is related to the slip of the preferentially oriented grains. Quasi-cracks often occur at the beginning of fatigue crack growth, which is a characteristic of dense hexagonal crystals. The micro-mechanism of further crack growth can be brittle or ductile, it can be either transgranular or intergranular, depending on the influence of metallurgical structure and environment. Generally lowering the temperature can prolong the crack initiation period and improve the fatigue life of magnesium alloys.
3. Electroplating of magnesium alloys
According to long-term research and practical results, the research and development work of magnesium alloy die casting manufacturers at home and abroad to solve the corrosion problem of magnesium alloys is mainly concentrated in the following three aspects:
1. Improve the corrosion resistance of magnesium alloys through alloying and the use of high-purity alloys;
2. Use a surface treatment or a coating technology to apply a protective coating on the magnesium alloy;
3. Design the continuous structure and assembly method of the alloy to reduce or avoid electrochemical corrosion.
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