Surface finishing techniques for metal materials
Anodic oxidation
It is mainly the anodizing of aluminum, which uses the electrochemical principle to form a layer of alumina film on the surface of aluminum alloy material. The oxide film has special characteristics of protection, decoration, insulation, and wear resistance.
Technical features:
1. Enhance strength
2. Realize any color except white
3. Nickel-free sealing is realized to meet the requirements of developed countries
Technical difficulties and improvement of key points:
The yield level of anodizing is related to the cost of the final product. The key to improving the yield of anodizing is the appropriate amount of oxidant, suitable temperature, and current density, which requires structural component manufacturers to explore and seek breakthroughs in the production process.
Electrophoresis
Used in stainless steel, aluminum alloy, and so on, can make the product appear various colors, and maintain metal luster, while enhancing the surface performance, with good corrosion resistance.
Advantage:
1. The color is rich;
2. No metal texture can cooperate with sandblasting, polishing, wire drawing, etc;
3. Processing in a liquid environment can realize the surface treatment of a complex structure;
4. The technology is mature and can be mass-produced.
Disadvantages:
The ability to cover up defects in general and the pre-treatment requirements for electrophoresis of die castings are high.
Micro arc oxidation
In the electrolyte solution (usually weak alkaline solution), a high voltage is applied to form a ceramic surface film layer, which is the result of the synergy between physical discharge and electrochemical oxidation.
Advantage:
1. Ceramic texture, dull appearance, no high gloss products, delicate handle, anti-fingerprint;
2. A wide range of substrates: Al, Ti, Zn, Zr, Mg, Nb, and their alloys;
3. Simple pretreatment, excellent corrosion resistance, weather resistance, and good heat dissipation performance.
Disadvantages:
At present, the color is limited, only black, gray and other mature, bright color is difficult to achieve at present; the cost is mainly affected by high consumption, which is one of the highest costs in surface treatment.
PVD coating
PVD, Physical vapor deposition, is a kind of industrial manufacturing technology, is mainly uses the physical process to deposit the film technology.
Standard Process:
Cleaning before PVD→entering the furnace and vacuuming→cleaning target and ion→coating→finishing coating, cooling out of furnace→post-treatment (polishing, AFP)
Technical features:
PVD (physical vapor deposition) can be used to coat the metal surface with high hardness and high wear resistance
Electroplate
This is a technology that uses electrolysis to make the surface of metal adhere to a layer of the metal film, to prevent corrosion, improve wear resistance, electrical conductivity, reflective property and enhance the beauty of technology.
Advantage:
1. The coating has high gloss and high-quality metal appearance;
2. The base materials are SUS, Al, Zn, Mg, etc., and the cost is lower than that of PVD.
Disadvantages:
Environmental protection is poor and the risk of environmental pollution is high.
Powder spraying
The powder coating is sprayed on the surface of the workpiece by powder spraying equipment (electrostatic spraying machine). Under the action of static electricity, the powder will be evenly absorbed on the surface of the workpiece to form a powder coating; the powder coating will be cured by high-temperature baking and leveling, and become the final coating with different effects (different effects of powder coating).
Advantage:
1. Rich colors. Both highlight and matte available
2. Low cost, suitable for building furniture products and heat sink shell, etc;
3. High utilization rate, 100% utilization, environmental protection
4. It can imitate the effect of the wood grain.