Surface Finishing Processes for Manufactured Parts
Guide to surface finishing processes available in China: polishing, anodizing, plating, powder coating, and sandblasting. Compare costs, quality, and applications for industrial buyers.
Surface finishing transforms raw manufactured parts into finished products. Choosing the right finish affects appearance, corrosion resistance, wear properties, and cost. Here is a practical guide to key finishing processes available from Chinese suppliers.
Polishing & Buffing
Mechanical abrasion to improve surface smoothness and appearance. Available in multiple grades from matte to mirror finish (Ra 0.4 down to 0.05 μm).
- Mechanical polishing: Abrasive wheels and compounds. Best for steel, aluminum, brass.
- Electropolishing: Electrochemical process for stainless steel. Removes micro-burrs and improves corrosion resistance.
- Barrel tumbling: Batch finishing for small parts. Cost-effective but less consistent.
- Cost: $0.50-3.00/piece depending on part size and finish level.
Anodizing (Aluminum)
Electrochemical process that creates a durable, corrosion-resistant oxide layer on aluminum surfaces.
- Type II (Sulfuric anodizing): Standard decorative and protective finish. Clear or dyed colors. Thickness 5-25 μm.
- Type III (Hard anodizing): Thicker coating (25-100 μm) for wear resistance on mechanical parts.
- Available colors: clear, black, red, blue, gold, and custom colors (minimum quantity usually required).
- Cost: $0.30-1.50/piece for Type II, $0.80-3.00/piece for Type III.
Electroplating
Applying a thin metal layer onto a substrate through electrolytic deposition.
- Zinc plating: Corrosion protection for steel. Clear, blue, yellow (hexavalent or trivalent chrome). $0.10-0.50/kg.
- Chrome plating: Decorative or hard chrome. Decorative for consumer products, hard chrome for industrial tooling. $0.50-2.00/dm².
- Nickel plating: Bright or matte nickel for appearance and corrosion resistance. Often used as undercoat for chrome. $0.30-1.00/dm².
- Tin plating: Solderable surface for electronic components. $0.20-0.60/dm².
Important: Ensure Chinese platers comply with RoHS regulations if your products ship to Europe. Request plating thickness test reports.
Powder Coating
Dry powder applied electrostatically and cured under heat. Produces durable, uniform, thick coatings in unlimited colors.
- Thickness: 60-120 μm (single coat), up to 250 μm (multi-coat)
- Colors: Any RAL color available. Standard colors shorter lead time.
- Cost advantage: No solvents, high material utilization (overspray recycled)
- Cost: $1.00-3.00/m² depending on color and batch size. Metallic and textured finishes cost more.
- Common finishes: Gloss (30-90 units), semi-gloss, matte, textured, wrinkle, metallic.
Sandblasting
Propelling abrasive media at high velocity to clean or texture surfaces. Prepares parts for subsequent coating or creates a uniform matte finish.
- Glass bead blasting: Smooth, satin finish. Best for decorative parts.
- Aluminum oxide blasting: Aggressive cleaning for scale and rust removal.
- Steel shot blasting: For heavy-duty cleaning of castings and forgings.
- Cost: $0.20-0.80/piece depending on part size and media type.
Process Selection Guide
| Requirement | Recommended Process |
| Corrosion protection (steel) | Zinc plating, powder coating, or painting |
| Corrosion protection (aluminum) | Anodizing (Type II) |
| Wear resistance (aluminum) | Hard anodizing (Type III) |
| Decorative appearance (metal) | Polishing + plating (Ni/Cr) or powder coating |
| Surface preparation for paint | Sandblasting or phosphating |
| High temperature application | Ceramic coating or specialist enamel |
| Budget-constrained decorative | Electrostatic painting or basic powder coating |