Coatings

Coatings modify a part’s surface to improve corrosion resistance, wear, appearance, and electrical properties without changing the base material or core geometry.

Overview

Coatings apply a controlled layer of material onto a finished part to change how the surface behaves without redesigning the base part. Options range from anodizing and powder coating to electroplating and PVD, letting you target corrosion protection, wear resistance, lubricity, conductivity, or cosmetic appearance. Thickness usually runs from a few microns (PVD, electroplating) up to hundreds of microns (powder coating).

Use coatings when the base material meets structural needs but the environment, aesthetics, or functional surface requirements demand more. They fit well for medium to very high volumes, since masking, racking, and process control benefit from repeatability. Tradeoffs include extra processing steps, potential dimensional growth, risk of edge build-up or recess starvation, and added inspection complexity. Upfront design for consistent coating thickness, grounding, and masking lines saves cost and rework.

Common Materials

  • Aluminum 6061
  • Mild steel 1018
  • Stainless steel 304
  • Stainless steel 316
  • Tool steel H13
  • Zinc die cast

Tolerances

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Applications

  • Automotive suspension components
  • Consumer electronics housings
  • Hydraulic fittings and manifolds
  • Fasteners and hardware
  • Medical device instruments
  • Aerospace brackets and hinges

When to Choose Coatings

Use coatings when the base material meets strength and cost targets but needs better corrosion resistance, wear performance, or appearance. They are ideal after machining or forming when you can accept controlled dimensional growth on non-critical surfaces. Coatings make the most sense where you have repeated parts and can standardize masking, fixturing, and specification control.

vs Machined Surface Finishing

Choose coatings when you need corrosion protection, color, or specific electrical/tribological properties that machining alone cannot deliver. Machined finishes only change texture and roughness; coatings change the surface chemistry and performance without further cutting the base material.

vs Polishing

Use coatings instead of polishing when functional performance (corrosion, wear, conductivity) matters more than pure gloss. Polishing improves appearance and reduces roughness but does not provide a protective barrier, while coatings can add both protection and targeted surface properties on top of a machined or lightly finished surface.

vs Painting

Choose dedicated coatings (powder coating, electroplating, anodizing) when you need better durability, adhesion, chemical resistance, or tighter thickness control than liquid paint typically offers. Coatings are preferable for high-wear, outdoor, or chemically aggressive environments where painted layers would chip, fade, or delaminate sooner.

vs Heat Treatment

Use coatings when you want to enhance surface properties without changing core hardness or mechanical behavior of the entire part. Heat treatment alters bulk properties; coatings localize improvements to exposed surfaces and can be applied after heat treat to avoid distortion or property changes.

vs Hard Coatings

Use general-purpose coatings when you mainly need corrosion protection, appearance, or basic wear resistance at lower cost and with simpler specs. Reserve advanced hard coatings (e.g., specialized PVD or CVD) for high-load sliding contacts, cutting tools, or extreme wear situations where standard coatings will not survive.

Design Considerations

  • Clearly define critical dimensions and specify whether they are before or after coating, including expected coating thickness on each relevant surface
  • Avoid deep blind holes, sharp internal corners, and tight gaps where coating may not reach or may bridge and seize mating parts
  • Design obvious, non-functional areas for fixturing and electrical contact; indicate acceptable clamp or contact marks on drawings
  • Call out coating type, standard, thickness range, color, and performance requirements (e.g., salt spray hours) to avoid ambiguous quotes
  • Minimize unnecessary masking by adjusting part geometry or tolerances so more surfaces can be fully coated without added labor
  • Communicate mating part fits and functional surfaces so the coater can adjust process, racking, and coverage to maintain assembly clearance