Metal vs. Plastic Coating Differences: Process Key Points Determined by Material Properties

Metal vs. Plastic Coating Differences: Process Key Points Determined by Material Properties

Due to significant differences in material properties between metals and plastics, their coating processes have essential distinctions in pretreatment, coating selection, construction parameters, and other aspects. The core goal of coating is to balance protectiveness and decorativeness, and the physical and chemical properties of materials directly determine the direction of process design. Only by accurately adapting to material properties can the coating adhesion, durability, and overall effect be guaranteed.

The core of coating metal materials (such as steel and aluminum alloy) is rust and corrosion prevention, with pretreatment being a key process. Steel parts need to undergo degreasing, pickling, and phosphating to remove oxide layers and impurities, enhancing coating adhesion; aluminum alloy parts adopt anodizing or chromating to avoid oxide films affecting adhesion. Coatings are mostly a combination of epoxy primer and polyurethane topcoat, balancing rust resistance and weather resistance. Spraying or electrophoresis can be used for construction, and the high-temperature environment must be controlled during drying to prevent metal deformation. In some scenarios, curing agents are also required to improve coating hardness.

Plastic materials (such as ABS and PP) have strong surface inertness and low polarity, making the improvement of adhesion the main difficulty in coating. Pretreatment does not require complex rust prevention steps, mainly relying on sanding roughening or plasma treatment to break the surface inert layer; for hard-to-adhere plastics like PP, additional primer must be applied to establish a connection bridge for the coating. Special plastic paints and acrylic paints are preferred to avoid solvent-based coatings corroding plastic substrates. During construction, spray pressure and distance should be controlled to prevent plastic deformation.

In addition, there are obvious differences in drying processes: high-temperature baking can be used for metal coating to accelerate curing, while plastics require low-temperature baking or natural air drying to avoid substrate aging and deformation caused by high temperatures. In summary, metal coating focuses on rust prevention and coating strength, while plastic coating emphasizes adhesion and substrate protection. Process design must fully rely on material properties to achieve ideal coating effects.