Painting

Painting applies a pigmented liquid film to parts for corrosion protection, color, and appearance, with thickness, masking, and cure controlling final performance.

Overview

Painting is a spray, dip, or brush-applied pigmented coating that dries or cures into a protective film. It’s commonly used to add color coding, improve cosmetic appearance, and provide light-to-moderate corrosion protection on metals and polymers. Typical paint systems include primers plus topcoats (epoxy, polyurethane, acrylic) matched to the environment and required gloss/texture.

Choose painting when you need flexible aesthetics (color, sheen, texture) and broad material compatibility at low to medium volumes. Tradeoffs: paint thickness can interfere with fits, threads, and sealing surfaces; coverage is limited in deep recesses and sharp corners; and durability depends heavily on surface prep, primer selection, and cure control. Expect lead time for masking and cure, and plan for touch-up risk on edges and handling surfaces.

Common Materials

  • Aluminum 6061
  • Steel 1018
  • Stainless steel 304
  • ABS
  • Polycarbonate
  • Glass-filled nylon

Tolerances

±0.003–0.010 in (critical fits must be masked; paint build typically 0.001–0.006 in total)

Applications

  • Instrument enclosures and panels
  • Industrial machine guards and frames
  • Automotive brackets and mounts
  • Hand tools and housings
  • Medical device covers (non-sterile exterior)
  • Color-coded fittings and assemblies

When to Choose Painting

Painting fits parts that need color, branding, or environmental protection without tight control of coating thickness. It works best on accessible surfaces with straightforward masking and moderate wear expectations. It’s well-suited to low-to-medium volumes where color changes and cosmetic requirements vary by program.

vs Machined Surface Finishing

Choose painting when surface texture and visual uniformity matter more than bare-metal appearance. Paint can hide minor machining marks and provides color and corrosion protection, but it can’t preserve tight fits or sharp detail without masking.

vs Polishing

Choose painting when you need color, opacity, or protection rather than a reflective bare substrate. Polishing improves appearance and cleanability but won’t provide a protective barrier comparable to a paint system, and polished surfaces often need extra prep for paint adhesion.

vs Coatings

Choose painting when you want a wide choice of colors/gloss/texture and straightforward touch-up or rework. Many functional coatings prioritize wear, chemical resistance, or controlled thickness; painting is typically more cosmetic/flexible but less abrasion-resistant than specialized systems.

vs Passivation

Choose painting when stainless needs cosmetic color or added barrier protection in mild environments. Passivation improves corrosion resistance by cleaning/conditioning the surface but doesn’t change color and won’t protect against abrasion or provide branding.

vs Hard Coatings

Choose painting when the part sees light contact and you need appearance or corrosion protection at lower cost. Hard coatings excel in wear and scratch resistance but usually limit color options and can be harder to repair locally.

Design Considerations

  • Call out paint system requirements (primer/topcoat type, color code, gloss, texture) and the service environment (UV, chemicals, salt) to avoid wrong coating selection
  • Define masked/no-paint areas clearly on drawings (threads, bearing bores, gasket lands, electrical grounds) and include masking tolerances
  • Avoid sharp external edges; add small radii/chamfers to reduce edge pullback and improve coating durability
  • Minimize deep pockets, blind cavities, and tight internal corners where spray coverage is inconsistent; add drain/vent paths if dipping
  • Specify acceptable cosmetic limits (orange peel, dust nibs, runs, touch-up zones) and inspection method for visible surfaces
  • Plan assembly interfaces for paint build (clearances, press fits, snap features) and identify surfaces that must remain dimensionally controlled