1. Poor corrosion resistance.
When the impurity elements of lead, cadmium and tin in the alloy composition exceed the standard, the casting will age and deform, show volume expansion, greatly reduce the mechanical properties (especially plasticity), and even break after a long time.
Lead, tin, and cadmium have very little solubility in zinc alloys, so they concentrate on grain boundaries and become cathodes. The aluminum-rich solid solution becomes the anode. In the presence of water vapor (electrolyte), it will promote intergranular electrochemical corrosion. Die-casting parts are aging due to intergranular corrosion.
2. Aging effect
The structure of zinc alloy is mainly composed of a zinc-rich solid solution containing Al and Cu and an Al-rich solid solution containing Zn, and its solubility decreases as the temperature decreases. However, due to the extremely fast curing speed of die-cast parts, the solubility of the solid solution is extremely saturated at room temperature. After a period of time, this supersaturation will gradually disappear, and the shape and size of the casting will also slightly change.
3. Zinc alloy die-casting shall not use parts in high temperature and low temperature (below 0℃) working environment. Zinc alloy has better mechanical properties at room temperature. However, both the tensile strength at high temperature and the impact performance at low temperature are significantly reduced.
4. Due to insufficient clamping force, poor mold clamping, insufficient mold strength and high melting temperature of zinc alloy die-casting, burrs may appear on the surface of the fragments. This phenomenon is called product shaving, which is often required by companies. The face-to-face post-treatment process is mainly solved by manual grinding, hydrogen-oxygen explosion and Zhaoling refrigerated shot blasting machine according to the nature of the product.
