Surface Finishing Services
Improve your part’s performance with high-quality surface finishing that optimizes smoothness, hardness, corrosion resistance, and overall appearance of your final components.
What is Surface Finish?
Surface finish refers to the texture and smoothness of a machined part’s outer surface. It plays a key role in both appearance and performance, influencing how components fit, move, and resist wear.
By controlling surface roughness, we can reduce friction, improve corrosion resistance, enhance sealing performance, and ensure every part meets the required precision and functional standards for its application.
Surface Treatment Process Control
Our surface treatment process control for CNC machined and die-cast parts ensures consistent quality and stable performance through standardized full-process management. Pre-treatment removes oil, rust, and residues through multi-stage rinsing. Core parameters — including temperature, concentration, and current — for anodizing, powder coating, electroplating, and painting are continuously monitored and verified. In-process inspections cover film thickness (±10% tolerance), adhesion (≥4B), and coating uniformity, while post-treatment includes corrosion resistance testing (salt spray ≥48–72h) and scratch-proof packaging. We maintain strict intra- and inter-batch consistency (color deviation ΔE ≤1.5) and adhere to standardized visual inspection conditions, ensuring reliable and compliant surface treatment results.
CNC Machining Surface Treatment
As Machined (Machined Finish)
Represents the natural surface condition after machining, featuring visible tool marks and a standard surface roughness of Ra 1.6–3.2 μm. Ideal for functional components or assemblies that do not require additional surface finishing.
Oil Spray
Creates a product with rich color and a uniform, eco-friendly coating. The surface of die castings must be cleaned, deoxidized, and chemically pretreated before spraying.
Anodizing
Enhances corrosion and wear resistance while allowing for color dyeing — ideal for aluminum components.
Polishing
Produces a smooth, high-gloss finish by reducing surface roughness and enhancing the visual appeal of metal parts.
Sand Blasting
Uses high-pressure abrasive media to clean and texture surfaces, resulting in a consistent matte or satin appearance.
Tumbling
Smooths and polishes small parts through friction and abrasion in a rotating barrel, delivering a uniform yet slightly textured finish.
Laser Carving
Removes or engraves material through localized melting and vaporization under focused laser irradiation, achieving precise and permanent markings.
Alodine (Chromate Conversion)
Provides excellent corrosion resistance and improves paint adhesion, primarily used on aluminum alloys.
Heat Treatment
Modifies the internal structure of metals to enhance hardness, strength, and toughness or to improve ductility.
Brushed Finish
Creates a fine, linear texture on the metal surface using abrasive belts or brushes, producing a satin-like, decorative appearance.
Powder Coating
Applies a dry powder that’s electrostatically charged and cured under heat to form a durable, wear-resistant, and colorful finish.
Electroplating
Deposits a thin layer of metal such as nickel, chrome, or zinc onto the surface to enhance corrosion resistance, wear resistance, and conductivity.
Pad Printing
Transfers images or text onto parts using a silicone pad, improving the visual appeal and branding of finished products.
Appearance Inspection & Acceptance Criteria
All surface finishing processes at ZH Precision follow strict quality control standards. Each component is inspected to ensure that its coating, texture, and color fully meet the surface finish specifications defined in customer drawings.
Consistency Requirements
- Surface must remain uniform in color, gloss, and texture, without visible tool marks, stains, or uneven coating.
- The same grit size and finishing process shall be applied across all parts to maintain a consistent appearance.
- Color variation between parts should not exceed ΔE ≤ 1.0 under standardized lighting conditions.
- No visible cracks, bubbles, peeling, pitting, or oxidation spots are permitted on the finished surface.
- Brushed or grain patterns must maintain uniform direction and density across all visible faces.
Visual Inspection Conditions
- Parts shall be inspected under uniform, neutral lighting of 500–1000 lux at a viewing distance of 30–50 cm.
- Surfaces must be free from visible defects such as scratches, dents, discoloration, and stains.
- Edges and corners should be smooth without burrs, flash, or sharp protrusions.
- Coating, plating, or anodizing layers must show no peeling, cracking, or contamination.
- Color and gloss are evaluated against the approved reference sample under standard daylight conditions.
Surface Finishing FAQ
At ZH Precision, we understand that every project has different surface finishing needs.
This FAQ section answers the most common questions about our finishing capabilities, materials, and quality standards — helping you choose the right process and understand how we ensure consistent, high-quality surface results for every part.
A: Surface finishing improves the appearance, corrosion resistance, hardness, and wear performance of metal parts. It also helps achieve smoother surfaces, tighter tolerances, and better adhesion for coatings or paints.
A: We support a wide range of materials, including aluminum, stainless steel, brass, copper, steel, zinc, magnesium, and die-cast alloys. The most suitable finishing process depends on the material’s characteristics and application requirements.
A: All finishing processes are standardized and controlled by our in-house surface treatment engineers. Key parameters such as temperature, voltage, and chemical concentration are continuously monitored. We also check color deviation (ΔE ≤1.5) and perform 100% visual inspections to ensure consistent appearance and quality.
A: Yes. We offer custom anodized colors, powder coating textures, and surface gloss levels according to Pantone or RAL color standards. Special finishes can also be developed based on your prototype or design requirements.
A: ZH Precision performs visual inspection under standardized lighting conditions and uses film thickness, adhesion, and corrosion resistance tests according to ISO and ASTM standards to ensure compliance and reliability.
