How to Select Coatings for Metal and Plastic Coating? Key Points for Material and Paint Selection

How to Select Coatings for Metal and Plastic Coating? Key Points for Material and Paint Selection

Metal and plastic workpieces feature vastly different material properties, and their paint coatings cannot be used interchangeably. Improper coating selection may trigger defects including poor adhesion, paint peeling, cracking, yellowing and insufficient corrosion resistance. When conducting metal‑plastic coating processing, enterprises shall make scientific selections according to substrate material, service environment, functional requirements and appearance standards. Balancing paint‑film adhesion, durability and visual quality helps cut rework costs and improve finished‑product qualification rates.

For metal workpieces, coating selection focuses on anti‑corrosion, wear resistance and high‑temperature resistance. Steel, carbon steel, aluminum alloy and other metal substrates are prone to oxidation and rust. A two‑layer structure of “primer plus topcoat” is adopted for basic solutions. Epoxy primer or anti‑rust primer is preferred as primer to seal metal substrates firmly against rust and boost adhesion. For topcoats, baking finish, polyurethane topcoat or powder coating can be selected for high hardness, scratch resistance, wear performance and acid‑alkali resistance. Outdoor metal workpieces require weather‑resistant coatings to prevent fading and chalking caused by long‑term sun and rain exposure, while industrial mechanical parts prioritize coatings with superior wear resistance and impact resistance.

For plastic workpieces, coating selection centers on adhesion and material compatibility. Plastic substrates such as ABS, PC and PP have low surface tension and poor paint‑holding capacity. Ordinary metal paints are prohibited to avoid paint peeling and cracking. Conventional plastic parts adopt special plastic primer matched with flexible topcoat. The coatings deliver high toughness to accommodate thermal expansion and contraction of plastics. Matte or glossy general topcoats work for common decorative plastic parts. Home‑appliance and precision housings require scratch‑resistant, anti‑yellowing eco‑friendly coatings, and low‑temperature spraying shall be adopted throughout to prevent workpiece deformation from high‑temperature baking.

The overall selection shall follow the principle of function matching. Indoor decorative workpieces prioritize texture, dust and stain resistance; outdoor ones emphasize weather and corrosion resistance; moving mechanical components focus on wear and impact resistance. By differentiating properties of metal and plastic substrates, adopting targeted coating systems and standardizing spraying processes, coated workpieces can obtain stable performance and fine appearance, meeting surface‑treatment standards for various industrial and civil products.