Surface Treatment and Finishing

Surface treatment and finishing modify a part’s surface to control corrosion, wear, appearance, friction, and cleanliness without changing its core geometry.

Overview

Surface treatment and finishing cover all processes that change how a part’s surface behaves: corrosion resistance, wear life, appearance, friction, and cleanliness. This category includes machined surface finishing (deburring, grinding), polishing, coatings (electroplating, conversion coatings), painting, heat treatment, surface texturing and marking, passivation, and hard coatings such as PVD or nitriding.

Use surface treatment and finishing when the base manufacturing process delivers the right geometry, but the surface needs better performance or a specific cosmetic grade. You can tune corrosion resistance, hardness, fatigue strength, cleanability, and branding without redesigning the part. The main tradeoffs are added cost, extra process steps, potential dimensional changes from coatings or heat treatment, and more detailed specifications and quality checks. Choosing the right sub-process depends on part material, service environment, required surface roughness, and budget. Combining compatible treatments (e.g., machining + heat treat + coating) often delivers the best performance-to-cost ratio.

Common Materials

  • Aluminum 6061
  • Steel 1018
  • Stainless steel 304
  • Titanium Grade 5
  • Inconel 718
  • ABS plastic

Tolerances

N/A – dimensional tolerances come from the base process; surface finish often 16–125 µin Ra and coating thickness 5–50 µm when specified

Applications

  • Hydraulic manifolds and valve bodies
  • Surgical instruments and implants
  • Automotive suspension and brake components
  • Smartphone and laptop housings
  • Injection mold cavities and cores
  • Food and pharmaceutical processing equipment

When to Choose Surface Treatment and Finishing

Choose surface treatment and finishing when the part’s geometry is set, but you need specific corrosion resistance, hardness, wear life, or cosmetic appearance. It fits both prototypes and production runs where surface performance is critical to reliability or customer perception. It’s also key when regulatory or industry standards call for defined surface conditions or passivation.

vs CNC machining

Use surface treatment and finishing when machining alone meets dimensional needs but not surface performance or appearance. Apply finishing to improve corrosion resistance, wear, or cosmetics without adding complex machining features. Specify machining for geometry first, then layer finishing operations to hit functional and cosmetic targets.

vs 3D printing

Choose surface treatment and finishing when printed parts need smoother surfaces, tighter sealing surfaces, or improved strength, hardness, or corrosion resistance. Post-process printing with machining, polishing, coatings, or heat treatment to turn near-net printed parts into production-ready components.

vs Casting

Select surface treatment and finishing when cast parts require better sealing surfaces, fatigue life, or appearance than as-cast surfaces can provide. Machine critical features, then apply polishing, coatings, or hardening to achieve durability and cosmetic requirements while keeping casting cost advantages.

vs Sheet metal fabrication

Use surface treatment and finishing when formed sheet parts need corrosion protection, specific textures, or branded appearance. Painting, powder coating, anodizing, or passivation transform basic brackets and enclosures into durable, customer-facing products.

vs Grinding

Grinding targets precise geometry and fine surface finish on critical features; surface treatments modify material properties and long-term performance. Use finishing when you already have the required profile or flatness from grinding but need better hardness, corrosion resistance, or cosmetic consistency across the entire part.

Design Considerations

  • Call out surface requirements explicitly: Ra targets, coating type and spec, color, gloss, and any areas to be masked
  • Avoid over-tight dimensional tolerances on coated features; specify either pre- or post-coating dimensions and expected thickness range
  • Round sharp edges and add small radii to improve coating coverage, reduce stress risers, and help with plating/painting flow
  • Group parts by material and finish to enable batch processing and reduce per-part finishing cost
  • Flag critical sealing or mating surfaces that must not be painted or heavily textured so shops can fixture and mask correctly
  • Confirm material compatibility with planned treatments (e.g., heat treat temperature limits, passivation chemistry, adhesion to plastics) before finalizing the design