Surface treatment is a process of artificially forming a surface layer with different mechanical, physical, and chemical properties from the substrate material on the surface of the base material.
The purpose of surface treatment is to meet the requirements of product corrosion resistance, wear resistance, decoration, or other special functions. Commonly used surface treatment methods include mechanical polishing, chemical treatment, surface heat treatment, spray coating, etc. Surface treatment involves cleaning, sweeping, deburring, degreasing, and removing oxide scales from the surface of workpieces. Let's explore some surface treatment techniques today.
Commonly used surface treatment techniques are：
1. Vacuum Metalizing:
Vacuum metalizing is a physical deposition phenomenon. It involves injecting argon gas in a vacuum, which strikes the target material to separate molecules and form a uniform and smooth metallic-like surface layer on the conductive substrate.
Applicable materials:
- Various materials can undergo vacuum metalizing, including metals, soft and hard plastics, composites, ceramics, and glass.
- Aluminum is the most commonly used material for surface treatment, followed by silver and copper
Process cost: The process involves spraying, loading, unloading, and respraying the workpiece, so the labor cost is relatively high, depending on the complexity and quantity of the workpieces.
Environmental impact: Vacuum metalizing has minimal environmental pollution, similar to the impact of spray coating on the environment.
2. Electropolishing:
Electropolishing is an electrochemical process where atoms of the immersed workpiece are converted into ions and removed from the surface due to the passage of electric current, resulting in the removal of fine burrs and increased brightness of the workpiece surface.
Applicable materials:
- Most metals can undergo electropolishing, with stainless steel being the most commonly used material (especially austenitic stainless steel).
- Different materials cannot be electropolished together, and they should not be placed in the same electropolishing solvent.
Process cost: Electropolishing is mostly automated, leading to lower labor costs.
Environmental impact: Electropolishing uses relatively mild chemicals and requires a small amount of water, simplifying the process and extending the corrosion resistance of stainless steel.
3. Pad Printing:
Pad printing is a specialized printing method that allows printing of text, graphics, and images on irregularly shaped objects' surfaces.
Applicable materials:Pad printing can be used on almost all materials except those softer than silicone pads, such as PTFE.
Process cost: Low mold cost and low labor cost.
Environmental impact: Pad printing involves the use of solvent-based inks, which contain harmful chemicals and can have a significant environmental impact.
4. Galvanizing:
Galvanizing is a surface treatment technique where a layer of zinc is applied to the surface of steel and iron alloy materials to provide aesthetic and anti-corrosion effects.
Applicable materials:Galvanizing relies on metallurgical bonding and is suitable for surface treatment of steel and iron.
Process cost: No mold cost, short processing time, and moderate labor cost, which depends on the manual surface treatment before galvanizing.
Environmental impact: Galvanizing extends the lifespan of steel and iron components by 40-100 years, effectively preventing rust and corrosion, making a positive contribution to environmental protection.
Additionally, galvanized components can be re-galvanized after their useful life ends, ensuring no chemical or physical waste from the reuse of liquid zinc.
5. Electroplating:
Electroplating is a process that involves depositing a layer of metal film on the surface of a part using electrochemical reactions, which enhances properties such as anti-oxidation, wear resistance, conductivity, reflectivity, and aesthetics. It is commonly used for coating coins.
Applicable materials:
Most metals can undergo electroplating, but different metals have varying levels of purity and plating efficiency. Commonly used metals for electroplating include tin, chromium, nickel, silver, gold, and rhodium. ABS plastics are frequently used for electroplating.
Process cost: No mold cost, but fixturing is needed to hold the parts during plating. Time and labor costs vary depending on temperature and the type of metal being plated. For example, plating silverware and jewelry require highly skilled workers due to high requirements for appearance and durability.
Environmental impact: Electroplating involves the use of a significant amount of toxic substances, requiring professional handling and extraction to minimize environmental impact.
6. Hydro Transfer Printing:
Hydro Transfer Printing is a method of printing colored patterns from transfer paper onto three-dimensional product surfaces using water pressure. It is becoming increasingly popular for product packaging and surface decoration requirements.
Process cost: No mold cost, but multiple products are transferred simultaneously using fixtures, and the time cost is generally not more than 10 minutes per cycle.
Environmental impact: Compared to product spray coating, hydro transfer printing makes more efficient use of printing coatings, reducing the risk of waste leakage and material wastage.
7. Screen Printing:
Screen printing is a technique where ink is forced through the mesh of a stencil onto a substrate to create a printed design or image. It is commonly used for various printed materials like colorful paintings, posters, business cards, book covers, product labels, and textiles.
Applicable materials:Almost all materials can be screen printed, including paper, plastics, metals, ceramics, and glass.
Process cost: Low mold cost, but it still depends on the number of colors, as each color requires a separate stencil. Labor costs can be high, especially for multi-color printing.
Environmental impact: Light-colored screen printing inks have a minimal environmental impact. However, inks containing PVC and formaldehyde have harmful chemicals and need proper recycling and treatment to prevent water pollution.
8. Anodic Oxidation:
Anodic oxidation, mainly applied to aluminum, is a process that generates a layer of Al2O3 (aluminum oxide) film on the surface of aluminum and aluminum alloy through electrochemical principles. This oxide film exhibits special properties such as protection, decoration, insulation, and wear resistance.
Applicable materials:Aluminum and aluminum alloy products are suitable for anodic oxidation.
Process cost: The production process consumes a significant amount of water and electricity, especially during the oxidation process. The machine itself requires continuous cooling with circulating water, resulting in an electricity consumption of around 1000 degrees per ton.
Environmental impact: Anodic oxidation is not particularly energy-efficient. Furthermore, the anodic effect in aluminum electrolysis production can produce gas that damages the ozone layer in the atmosphere.
9. Metal Wired:
Metal wiring is a surface treatment method where product surfaces are ground to form linear patterns, providing a decorative effect. The process can be divided into straight-line wiring, random wiring, corrugation, and spiral wiring, depending on the resulting patterns.
Applicable materials:Almost all metal materials can undergo metal wiring.
Process cost: The method is simple, and the equipment and material consumption are minimal, making it a cost-effective and high-efficiency process.
Environmental impact: Pure metal products have no paint or any chemical substances on the surface. They do not burn at 600 degrees Celsius and do not produce toxic gases, meeting composite fire protection and environmental requirements.
10. In-Mold Decoration (IMD):
IMD involves placing pre-printed film sheets inside a metal mold, and then injecting the molding resin into the mold to bond the printed film with the resin, creating a fully-formed product.
Applicable Material: Plastic Surface
Process Cost: Only requires one set of molds, which reduces costs and saves labor through automated production. The process is simplified, using a single injection molding method to achieve both shaping and decoration simultaneously.
Environmental Impact: This technology is environmentally friendly, avoiding the pollution caused by traditional painting and electroplating methods.
