What are the properties and application characteristics of zinc and zinc alloys

       Zinc is a silver-white metal with metallic luster. The melting point is 419 degrees, the density is 7.14g/cm3, and the standard electrode potential is -0.76V. It is one of the more active metals. The crystal structure of zinc is hexagonal close-packed and exhibits an allotropic transition with increasing temperature.

    The appearance of zinc coating is dark white, and the coating density is generally 6.27g/cm3. It is the earliest and most widely used coating material in thermal spraying anti-corrosion construction. However, zinc coatings do not have corrosion resistance in sulfur or oxide-contaminated air. Although the passivation of zinc is very small, it can be significantly passivated in chromate solution to form a zinc chromate protective film.

    The zinc raw material for thermal spraying requires high purity, the purity of Zn for anti-corrosion is required to be more than 99.995%, and the iron content is less than 0.001%. The purity of the wire is at least 99.9% zinc and below 0.05% Cu. In order to prevent the wire from being interrupted by spraying, the tensile strength is required to be greater than 150Mpa and the elongation is greater than 40%. The purity is ultra-high, and the finer the sprayed particles, the denser the coating surface. .

    1) The zinc-aluminum alloys used in thermal spraying are mainly zinc-aluminum binary alloys with an AI content of 5% to 25%. When the aluminum content in the alloy is greater than 28%, many chemical and electrochemical properties of the alloy are similar to those of pure aluminum. If it is used for thermal spraying anticorrosion, it cannot play a good role in cathodic protection. On the other hand, due to the increased aluminum content in the alloy, it is difficult to process the alloy wire, so the binary zinc-aluminum alloy containing 85% zinc and 15% aluminum is currently commonly used. The general grade of this alloy is Zn-AI15.

    2) Zn-AI15 alloy

The melting point of Zn-AI15 alloy is 440 degrees Celsius, and the coating density is about 5.0g/cm3. Zn-AI15 zinc-aluminum alloy is a coating with a two-phase structure that is superior to pure zinc or pure aluminum in many aspects. The alloy coating has good corrosion resistance in many environments and can provide effective protection for steel substrates. At present, there is also a commercial supply of Zn-AI15 alloy thermal spraying wire in my country.

    The mechanical properties of the Zn-AI15 alloy coating are better, and its strength and hardness are better than those of the pure zinc coating and the pure aluminum coating; advantage. The application in corrosion protection of steel structures is similar to that of zinc or aluminum. Therefore, the comprehensive performance of Zn-AI alloy coating is better than that of zinc coating and Ra coating, and it is an efficient electrochemical cathodic protection corrosion-resistant coating at room temperature.