Surface painting is a specialized form of surface treatment for stamped parts, focused on applying pigmented coatings to enhance aesthetics, provide color coding, and offer basic protection against environmental factors. Unlike general surface spraying (which may use non-pigmented functional coatings), painting prioritizes visual appeal while still delivering moderate resistance to corrosion, scratches, or fading. Stamped parts such as automotive body panels, household appliances, furniture components, and decorative hardware rely on surface painting to meet consumer design preferences and brand identity requirements.

The surface painting process for stamped parts is a structured workflow that begins with pre-treatment, progresses through primer, basecoat, and clearcoat application, and ends with curing and quality control. Pre-treatment is identical to that in surface spraying but with added emphasis on surface smoothness, as any imperfections will be visible in the final painted finish. For example, stamped steel automotive doors undergo degreasing, phosphating (to form a corrosion-resistant zinc phosphate layer), and sealing before painting to ensure a flawless base. The primer layer is the first coat applied, serving as a bonding agent between the part’s surface and the topcoat, while also filling minor surface irregularities. Primer formulations vary by material: epoxy primers are used for ferrous metals (steel, iron) to prevent rust, while acrylic primers are suitable for non-ferrous metals (aluminum, copper) and plastics. The primer is applied via spraying (HVLP or electrostatic methods) and cured at 60-100°C for 20-30 minutes, forming a smooth, uniform base 10-20 μm thick.

The basecoat is the pigmented layer that provides the desired color and appearance. It is available in a wide range of formulations, including solid colors (e.g., black, white, red), metallic finishes (containing aluminum or mica flakes for a shimmer effect), and pearlescent finishes (with iridescent particles). For stamped parts like refrigerator doors or washing machine panels, solid-color basecoats are common, while automotive body panels often use metallic or pearlescent basecoats to enhance visual appeal. The basecoat is applied in thin layers (5-15 μm per layer) to avoid runs or sagging, with each layer cured briefly before the next. Electrostatic spraying is preferred for basecoat application, as it ensures even coverage and minimizes overspray—critical for achieving consistent color across large batches of stamped parts.

The clearcoat is the final protective layer, applied over the basecoat to enhance gloss, resist scratches, and protect against UV radiation (which can cause fading). Clearcoats are typically acrylic or polyurethane-based, offering high durability and flexibility. They are applied in 20-30 μm thick layers and cured at 120-160°C for 30-60 minutes (for automotive parts) or air-cured for consumer goods with lower heat resistance. For example, stamped aluminum bicycle frames are painted with a basecoat (matching the brand’s color) and a clearcoat to withstand outdoor elements and prevent scratches from use. Post-painting quality control includes color matching (using spectrophotometers to ensure consistency with design standards), gloss measurement (with a gloss meter, typically 60-80 gloss units for high-gloss finishes), and adhesion testing. Surface painting not only transforms the appearance of stamped parts but also adds a protective barrier, extending their lifespan in both indoor and outdoor applications. Its ability to be customized to specific colors and finishes makes it a cornerstone of product design in consumer and industrial markets.