Q:What is hot-dip galvanizing, electro-galvanizing and aluminum galvanizing?
A:Hot-dip galvanizing: By immersing the steel in molten zinc at about 450°C, the zinc layer is metallurgically bonded to the substrate to form a thicker (usually 20-300g/m²) anti-corrosion coating.
Electrogalvanizing: Using the principle of electrolysis, zinc ions are deposited on the surface of the steel at room temperature to form a uniform but thinner (usually 3-20g/m²) coating without metallurgical bonding.
Aluminum galvanizing: Hot-dip 55% aluminum, 43.4% zinc and 1.6% silicon alloy coating (such as AZ150), which combines the high temperature resistance of aluminum and the cathodic protection of zinc, and the corrosion resistance is 2-6 times that of pure zinc.
Q：Which galvanizing method has the best anti-corrosion performance?
A：Aluminum galvanizing has the best anti-corrosion performance, and its corrosion resistance is 2-6 times that of pure zinc plating. It is especially suitable for extreme environments such as high temperature, high humidity or coastal areas; hot-dip galvanizing is second and is suitable for ordinary outdoor corrosion protection; electro-galvanizing has the weakest corrosion resistance and needs to be used in conjunction with painting.
Q：What is the difference in surface appearance between hot-dip galvanizing and electro-galvanizing?
A：Hot-dip galvanizing:
Obvious zinc flowers: due to the natural crystallization of liquid zinc during solidification, the surface presents irregular shiny zinc flowers (the size can be controlled, such as ordinary zinc flowers N, small zinc flowers M);
Slightly rough: the coating is thicker and has a slight bumpy feel to the touch, which is suitable for industrial scenes.
Electrogalvanizing:
Uniform and without zinc flowers: the electrolytically deposited zinc layer is delicate and smooth, with a uniform matte or bright silver color;
Extremely smooth: suitable for direct spraying or as an exterior part (such as home appliance panels, car interiors).
Q:Why is the zinc layer of electroplated galvanized thinner?
A:1. Process principle limitation: Electrogalvanizing deposits zinc ions in the electrolyte layer by layer on the steel surface, and the deposition speed is slow (only micrometers/hour), while hot-dip galvanizing is directly immersed in molten zinc liquid, which can quickly form a thick layer.
2. Functional demand orientation: Electrogalvanizing is mainly used for precision parts (such as electronic parts and home appliance panels), which need to ensure smooth surface and dimensional accuracy. Too thick zinc layer will affect subsequent processing such as stamping and welding.
3. Cost and efficiency balance: The longer the electroplating time, the thicker the zinc layer, but it will significantly increase energy consumption and production time, and the economy is poor. A thin layer can meet the basic anti-rust requirements (usually need to be combined with coating to enhance protection).
Q:Which type of galvanizing is commonly used in the automotive industry?
A：Hot-dip galvanizing is suitable for the following parts: Body structural parts (such as floor, longitudinal beam, anti-collision beam) - thick zinc layer (60-120g/m²), anti-stone impact corrosion.
Chassis parts (suspension components, fuel tank bracket) - strong corrosion protection is required in outdoor humid environment.
Advantages: low cost, strong corrosion resistance, suitable for hidden or high stress parts.
Applicable parts for electrogalvanizing: Appearance parts (doors, hood panels) - thin coating (10-20g/m²), smooth surface and easy to paint.
Precision parts (screws, connectors) - high dimensional accuracy requirements to avoid zinc spangles affecting assembly. Advantages: uniform and without zinc spangles, directly adapted to the painting process, high aesthetics.
Special uses for aluminum galvanizing: exhaust pipes, brake parts (high temperature resistance requirements), but it is rarely used.