The surface treatment process in product design is a key part of enhancing the texture, function and aesthetic value of the product, not only improving the appearance, but also enhancing the material properties (such as wear resistance, corrosion resistance, haptics, etc.). The following is an explanation of process classification, core role, mainstream process analysis and design trends to help designers choose the best solution according to product positioning and needs.

First, the core role of surface treatment
Functional improvements

Protection: anti-corrosion (such as metal plating), wear-resistant (such as hardening), insulation (such as spraying insulating varnish).

Physical properties optimization: thermal conductivity (e.g., aluminum alloy anodizing increases heat dissipation), anti-slip (e.g., texture treatment), hydrophobic and oleophobic (e.g., nano coating).

Aesthetic shaping

Texture expression: matte / high-gloss, metallic luster, wood grain / stone grain and other biomimetic textures.

Colors and patterns: Diversified colors and logo designs are achieved through spraying, silk screen printing, electroplating, etc.

User experience enhancements

Haptic optimization: fine matte (e.g. mobile phone cover glass AG process), skin-friendly coating (e.g. rubber paint), uneven and convex lines (e.g. non-slip buttons).

Interactive guidance: Distinguish functional areas (e.g., translucent coating of keys, special texture of touch areas) by surface treatment.

2. Classification and analysis of mainstream surface treatment processes
1. Coating process (overlay treatment)
A coating is formed on the surface of the substrate through spraying, printing, etc., to change the appearance and performance.

Painting

Ordinary paints: matte/glossy paints (such as home appliance shells), which are low cost but less environmentally friendly.

Metallic paint: add aluminum/copper powder to give a metallic luster (e.g. car body).

Rubber paint (hand paint): smooth to the touch, anti-fingerprint (such as the back cover of a mobile phone).

UV paint: UV curing, high hardness, good gloss (e.g. furniture panels).

Process principle: use a spray gun to atomize paint or paint and attach it to the surface, and dry it to form a paint film.

Type:

Design points: The influence of coating thickness (usually 30~50μm) on the product size should be considered, and complex curved surfaces need to be treated with anti-sagging.

Electroplating

Decorative plating: bright chrome (mirror effect, e.g. bathroom hardware), pearl nickel (soft metallic feel, e.g. in the middle frame of a mobile phone).

Functional plating: galvanized (anti-corrosion), silver-plated (conductive), hard chrome plating (wear-resistant).

Process principle: The electrolytic reaction is used to coat a metal film (such as chromium, nickel, copper) on the surface of metal or plastic.

Type:

Environmentally friendly alternative processes: cyanide-free plating, vacuum plating (e.g. PVD/CVD, see below).

Screen Printing

Process characteristics: Through screen printing patterns or functional coatings (such as conductive inks, shading inks), multi-color overprinting and special effects (such as luminous, fluorescent) are supported.

Application scenarios: electronic device LOGO (such as notebook computer A-side), key characters, automotive dashboard logo (see detailed description of surface screen printing process).

2. Surface modification process (substrate itself changes)
Physical or chemical changes to the surface structure of the substrate to improve performance.

Anodizing

Process principle: Aluminum and aluminum alloys form an oxide film (Al₂O₃) in the electrolytic cell, which can be dyed or sealed.

Advantages: strong corrosion resistance, high surface hardness (up to 200~300HV), support matte, sand, mirror and other effects (such as the "space gray" anodizing of Apple MacBook cases).

Color control: Rich colors (e.g. rose gold, blue) by electrolytic coloring or organic dyeing.

Abrasive Blasting & Brushing

Sandblasting: High-pressure blasting of sand particles (such as alumina, glass beads) roughens the surface to form a matte sanding effect (such as aluminum alloy furniture handles), which can be subsequently oxidized or sprayed.

Wire drawing: Use sandpaper or wire drawing wheels to pull parallel lines (such as straight grain, chaotic grain) on the metal surface to enhance the metal texture (such as stainless steel kitchen appliance panels).

Chemical Etching

Process principle: Corrosion of metal surface with strong acid/strong alkali solution to form concave and convex textures or patterns (such as the etched LOGO of the middle frame of the mobile phone).

Features: High precision (minimum line width 0.05mm), can achieve imitation metal forging texture or anti-slip concave points.

3. Thin Film Process (Vacuum Coating)
The film is deposited physically or chemically in a vacuum environment to achieve a high-quality appearance.

PVD (Physical Vapor Deposition)

Environmentally friendly (no electroplating pollution), strong adhesion, rich colors (such as rose gold, gun black);

It can achieve a "quasi-plating" effect and is used on substrates such as plastics (such as ABS), metal, and glass (such as the PVD coated middle frame of Xiaomi mobile phones).

Process principle: The metal target is evaporated/sputtered and deposited on the surface of the substrate to form nanoscale thin films (such as titanium, zirconium, stainless steel).

Advantage:

CVD (Chemical Vapor Deposition)

Process characteristics: Ceramic films (such as SiC, TiN) are generated by chemical reactions, with extremely high hardness (close to diamond), and are used for cutting tools and wear-resistant parts.

4. Composite process (combination of multi-layer treatment)
Anodizing + silk screen printing: Aluminum products are oxidized and colored first, and then silk screen printed with patterns (such as translucent characters on the surface of the mouse).

PVD Coating + Sandblasting: The metal substrate is sandblasted to form a rough surface, and then coated with a thin film to enhance adhesion and texture (e.g. anti-slip coating for camera bodies).

Spraying + Laser Engraving: Spray a solid color coating, then use the laser to engrave a translucent pattern (such as keyboard backlit characters).

3. Design Trend: From Single Function to Multiple Innovation
Sustainability & Environmental Protection

Material selection: Promote water-based coatings, recyclable coatings (e.g., chrome-free passivation), bio-based coatings (e.g., vegetable resins).

Process optimization: reduce the discharge of electroplating wastewater, and replace traditional chemical pretreatment with low-temperature plasma treatment.

Haptic and interactive innovation

Biomimetic Touch: Simulates natural textures (e.g. the warmth of pebbles, the roughness of tree bark) through CNC engraving or mold molding.

Dynamic surfaces: Temperature-sensitive color-changing coating (e.g., a water cup that develops color when heated), pressure-sensitive textures (e.g., enhanced haptic feedback on keys).

Micro-nano technology and functional integration

Nano coatings: hydrophobic and oleophobic (e.g., AF anti-fingerprint coating for mobile phone screens), self-healing coatings (e.g., automatic repair of scratches on automotive paint).

Optical function: Microstructure coating enables anti-glare (AG process), anti-reflection effect (e.g. camera lens coating), or holographic projection pattern.

Mixed Reality (MR) Fusion

Diffuse reflection of light or infrared sensing is achieved by means of a special coating on the surface of the smart device (e.g., the translucent coating of AR glasses is integrated with the sensor).

Fourth, process selection logic and design suggestions
Based on substrate properties

Metals: preferential anodizing, electroplating, PVD (e.g. anodizing for aluminum alloys, brushed + electroplating for stainless steel).

Plastic: suitable for spraying, water transfer printing, vacuum plating (such as ABS plastic needs to be flame treated to enhance adhesion).

Glass / Ceramic: Silk screen printing, coating (e.g. AG sandblasting + AF coating for mobile phone cover glass).

Balance cost with effectiveness

Small batch customization: choose spraying, silk screen printing, laser marking (no need to open the mold, low cost).

High-volume production: Priority is given to the mold forming process (e.g. direct molding of the texture during injection molding) or electroplating (evenly sharing the stencil/coating cost).

Testing & Validation

Key performance tests: adhesion (100 grid method), corrosion resistance (salt spray test), abrasion resistance (friction testing machine).

Environmental simulation test: high temperature and high humidity (such as automotive interior parts need to withstand 80°C aging), ultraviolet radiation (outdoor products anti-fade).

summary
Surface treatment is the key link of product design from "concept" to "texture", designers need to deeply understand the characteristics of the process (such as cost, precision, environmental protection), combine user experience goals and technology trends, and create products with both functional and emotional value through the ultimate play of a single process or the innovative combination of composite processes. In the future, with the progress of material science and intelligent manufacturing, surface treatment will become more intelligent, green and functionally integrated, opening up more possibilities for product design.