Coatings

Coatings add a controlled surface layer to improve corrosion resistance, wear, appearance, or conductivity, with properties driven by chemistry, thickness, and prep quality.

Overview

Coatings are applied surface layers—metallic, ceramic, or polymer—that modify a part’s outer performance without changing the base material. Common coating families include electroplating (zinc, nickel, gold, etc.), conversion/oxide coatings (anodizing), organic finishes (powder coating, e-coat), and thin-film deposition (PVD). The coating system is typically defined by the coating type, thickness range, surface prep, and post-treatment/sealing.

Choose coatings when the part’s function is dominated by surface behavior: corrosion protection, abrasion resistance, electrical contact performance, lubricity, or cosmetic color/texture. Tradeoffs are that coatings can affect fit, masking adds cost, and edge coverage, adhesion, and uniform thickness depend heavily on geometry and prep. Many coatings require careful handling after finishing and may need bake, seal, or passivation steps to meet durability and corrosion specs.

Common Materials

  • Aluminum 6061
  • Steel 1018
  • Stainless Steel 304
  • Copper C110
  • Brass C360
  • Titanium Grade 2

Tolerances

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Applications

  • Automotive brackets and fasteners
  • Aluminum electronics enclosures
  • Hydraulic fittings and manifolds
  • Electrical busbars and connectors
  • Medical instrument housings
  • Wear surfaces on tooling components

When to Choose Coatings

Choose coatings when you need a defined surface property (corrosion resistance, wear resistance, electrical performance, or appearance) without changing the core part material. It fits prototypes through production as long as you can control masking, racking/fixturing, and inspection of critical surfaces. It’s most effective when the drawing clearly calls out coating type, thickness, and any required corrosion or adhesion performance standard.

vs Machined Surface Finishing

Choose coatings when a bare machined finish won’t meet corrosion, wear, or electrical requirements. Coatings provide a measurable functional layer and can add color/reflectivity, but they can change fit and require masking of precision features.

vs Polishing

Choose coatings when you need durability and environmental resistance, not just improved appearance or reduced roughness. Polishing can support coatings by improving cleanliness and uniformity, but it doesn’t provide sacrificial protection, hardness, or controlled conductivity by itself.

vs Painting

Choose coatings when you need tighter control of thickness, better adhesion to metal substrates, higher wear resistance, or engineered properties like conductivity or lubricity. Painting can be faster for large cosmetic surfaces, but many engineered coatings outperform it for abrasion, chemical exposure, and contact surfaces.

vs Passivation

Choose coatings when the part needs an added barrier layer, sacrificial protection, or cosmetic finish beyond what passivation provides. Passivation improves stainless corrosion behavior but doesn’t add thickness or change wear properties the way plated, anodized, powder, or PVD coatings do.

vs Hard Coatings

Choose general coatings when corrosion protection, appearance, or electrical performance drives requirements more than extreme hardness. Hard coatings target wear and friction performance but can be higher cost and more sensitive to geometry and surface prep.

Design Considerations

  • Call out coating type, thickness (or class), and the governing spec/standard on the drawing so the shop can quote and certify correctly
  • Identify and dimension any no-coat/masked areas (threads, sealing faces, bearing bores) and specify whether post-coat machining is allowed
  • Allow clearance for coating buildup on mating features; avoid relying on a coating to “fix” a tight tolerance stack
  • Add racking/fixturing points or non-cosmetic areas for hooks/contacts to prevent witness marks on critical surfaces
  • Avoid sharp external edges and burrs; specify edge breaks to improve coverage and reduce burn-through or thin spots
  • Specify surface prep requirements (cleaning, blast, Ra) where adhesion, electrical contact resistance, or cosmetics are critical