China Aluminum Industry Network - Hot-dip aluminum coating involves immersing pre-treated metal components into a molten aluminum bath for a specific duration. After removal, a thin layer of aluminum adheres to the surface, providing protection against corrosion and enhancing durability. This process is widely used in industries such as construction, automotive, and electrical engineering. (1) **Mechanism of Hot-Dip Aluminum Coating** The mechanism of hot-dip aluminum is similar to that of hot-dip galvanizing. When molten aluminum comes into contact with iron-based materials, an initial reaction occurs at the interface, forming the FeAl3 compound. As the process continues, diffusion takes place within this FeAl3 layer. Due to concentration changes, a region rich in Fe2Al5 begins to form on the surface of the FeAl3 layer. With further diffusion of aluminum, the Fe2Al5 phase grows into columnar crystals, while the FeAl3 phase gradually diminishes. This intermetallic structure plays a crucial role in determining the adhesion and quality of the coating. (2) **Structural Characteristics of the Aluminum Layer** The resulting coating can be generally divided into two distinct layers. The outer layer is primarily composed of aluminum, forming a relatively uniform and dense surface. Beneath it lies a sublayer made up of an aluminum-iron alloy, mainly consisting of the Fe2Al5 intermetallic phase. A small amount of FeAl3 may also be present. The Fe2Al5 phase tends to grow in a tongue-like manner into the base metal, creating a strong bond. However, this phase is known to be hard and brittle, so its thickness should be carefully controlled—ideally no more than 1/10 of the total penetration layer. To achieve optimal results, the immersion temperature should be maintained between 700°C and 730°C. Additionally, adding 2% to 6% beryllium to the molten aluminum can significantly reduce the thickness of the Fe2Al5 layer, improving the overall quality and performance of the coating. These adjustments help ensure a more uniform and durable protective layer, making the process suitable for a wide range of industrial applications.
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