Properties and application characteristics of zinc and zinc alloys

Zinc is a silvery-white metal with a metallic luster. It has a melting point of 419°C, a density of 7.14 g/cm³, and a standard electrode potential of -0.76 V, making it one of the more reactive metals. Its crystal structure is hexagonal close-packed, and it undergoes allotropic transformation as temperature increases. The appearance of zinc coatings is typically dark white, with a density of around 6.27 g/cm³. Zinc has been widely used as a coating material in thermal spraying for corrosion protection due to its early adoption and effectiveness. However, it is not resistant to sulfur or oxide-rich environments. Although zinc exhibits minimal passivation, it forms a protective zinc chromate layer when exposed to chromate solutions. For thermal spraying, high-purity zinc is essential, especially for anti-corrosion applications, where the purity should be at least 99.995%, with iron content below 0.001%. The wire used must have a minimum zinc purity of 99.9% and copper content less than 0.05%. To ensure smooth spraying, tensile strength should exceed 150 MPa, and elongation should be over 40%. Higher purity leads to finer particles and a denser coating surface, enhancing the overall quality of the application. Zinc-aluminum alloys are commonly used in thermal spraying. A typical binary alloy contains between 5% and 25% aluminum. When the aluminum content exceeds 28%, the alloy's properties become similar to those of pure aluminum, which may reduce its cathodic protection performance. Additionally, higher aluminum content makes the alloy harder to process into wire. Therefore, a common composition is Zn-Al15 (85% zinc, 15% aluminum), known for its balanced properties. Zn-Al15 alloy has a melting point of 440°C and a coating density of approximately 5.0 g/cm³. This two-phase alloy offers better corrosion resistance than pure zinc or aluminum, providing effective protection for steel substrates. In China, Zn-Al15 thermal spray wires are commercially available. The alloy also exhibits superior mechanical properties compared to pure zinc or aluminum coatings, with improved strength and hardness. Its electrochemical behavior falls between that of zinc and aluminum, and in some cases, it performs better. It is widely used for corrosion protection on steel structures, offering an efficient, low-temperature cathodic protection solution. Concerned about surprises Label: zinc alloy Previous: Characteristics, structure and use of aluminum substrate Next: Application of magnesium in medicine

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