Surface treatment is a surface protection technology that can improve the corrosion resistance and wear resistance of products by changing the mechanical, physical and chemical properties of the surface layer of the base material. The traditional surface treatment methods mainly include: galvanizing, electrophoresis, blueing, blackening, passivation, phosphating, spraying, coloring, baking, infiltration, shot blasting, etc. However, at present, a variety of surface processing technologies have been widely developed and applied to the decoration of metal, glass, plastic and other material components or other special functional requirements to achieve excellent performance in corrosion resistance, appearance, texture, function and other aspects.

1、 Anodic oxidation

Anodic oxidation: mainly refers to the anodic oxidation of aluminum, which uses the electrochemical principle to generate a layer of Al2O3 (aluminum oxide) film on the surface of aluminum and aluminum alloy. This oxide film has special characteristics such as protection, decoration, insulation and wear resistance.

Monochrome and gradient color: polishing/sandblasting/drawing → degreasing → anodizing → neutralization → dyeing → hole sealing → drying

Dual color: ① polishing/sand blasting/wire drawing → degreasing → shielding → anodizing 1 → anodizing 2 → hole sealing → drying

② Polishing/sandblasting/wire drawing → degreasing → anodizing 1 → radium carving → anodizing 2 → hole sealing → drying

Technical features:

1. Lifting strength,

2. Realize any color except white.

3. Realize nickel-free hole sealing to meet the requirements of Europe, the United States and other countries for nickel-free.

Technical difficulties and key points for improvement:

The yield level of anodizing is related to the cost of the final product. The key to improve the yield of anodizing is the appropriate amount of oxidant, the appropriate temperature and current density. This requires the structural parts manufacturers to constantly explore and seek breakthroughs in the production process.

2、 ED-Electrophoresis position

Electrophoresis: used for stainless steel, aluminum alloy, etc., which can make the product present various colors, maintain the metallic luster, and enhance the surface performance, with good corrosion resistance.

Process flow: pretreatment → electrophoresis → drying

Technical features:

advantage:

1. Rich color;

2. It has no metal texture and can be used for sand blasting, polishing, wire drawing, etc;

3. Processing in liquid environment can realize surface treatment of complex structure;

4. The process is mature and can be mass produced.Disadvantages: the ability to cover defects is general, and the requirements for pretreatment of die-casting parts by electrophoresis are high

3、 Microarc oxidation (MAO)

Micro arc oxidation: the process of applying high voltage in electrolyte solution (generally weak alkaline solution) to generate a ceramic surface facial mask layer. This process is the result of the synergistic effect of physical discharge and electrochemical oxidation.

Process flow: pretreatment → hot water washing → MAO → drying

Technical features:

advantage:1. Ceramic texture, dull appearance, no high-gloss products, delicate feel, anti-fingerprint;

2. Wide range of substrates: Al, Ti, Zn, Zr, Mg, Nb, and their alloys;3. The pretreatment is simple, the product has excellent corrosion resistance, weather resistance and heat dissipation performance.

Disadvantages: At present, the color is limited, only black and gray are mature, and bright colors are difficult to achieve at present; The cost is mainly affected by the high consumption film, which is one of the highest costs in surface treatment.

4、 PVD vacuum plating

Physical vapor deposition (PVD): It is a kind of industrial manufacturing process, which mainly uses physical processes to deposit thin films.

Process flow: PVD pre-cleaning → furnace vacuumizing → target cleaning and ion cleaning → coating → coating completion, cooling out of furnace → post-treatment (polishing, AFP)

Technical features: PVD (Physical Vapor Deposition) can be used to coat metal surface with high hardness and high wear resistance cermet decorative coating

5、 Electroplating

Electroplating: It is a technology that uses electrolysis to attach a layer of metal film on the surface of the metal to prevent corrosion, improve wear resistance, conductivity, reflectivity, and enhance aesthetics.Process flow: pretreatment → cyanide-free alkaline copper → cyanide-free white copper and tin → chromium plating

Technical features:

advantage:

1. High gloss coating, high quality metal appearance;

2. The base materials are SUS, Al, Zn, Mg, etc; The cost is lower than PVD.

Disadvantages: poor environmental protection and high risk of environmental pollution.

6、 Powder coating

Powder spraying: powder coating is sprayed onto the surface of the workpiece with powder spraying equipment (electrostatic spray machine). Under the action of static electricity, the powder will evenly adsorb on the surface of the workpiece to form a powdery coating; The powder coating becomes the final coating with different effects (different kinds of effects of powder coating) after high temperature baking, leveling and curing.

Process flow: loading → electrostatic precipitator → spraying → low temperature leveling → baking

Technical features:

advantage:

1. Rich colors, high gloss and matte optional;2. Low cost, suitable for building furniture products and heat sink shells;

3. High utilization rate, 100% utilization, environmental protection;

4. Strong ability to mask defects;

5. It can imitate wood grain effect.Disadvantages: At present, it is rarely used in electronic products.

7、 Metal wire drawingWire drawing: It is a surface treatment method that forms lines on the surface of the workpiece by grinding products to achieve decorative effects. According to the different patterns after drawing, it can be divided into: straight drawing, random drawing, ripple, and spiral drawing.

Technical features:

Wire drawing treatment can make the metal surface obtain non-mirror metallic luster, and at the same time, wire drawing treatment can also eliminate the fine defects on the metal surface.

8、 SandblastingSand blasting: It is a process that uses compressed air as the power to form a high-speed spray beam to spray the sprayed material onto the surface of the workpiece to be treated at high speed, so as to change the appearance or shape of the outer surface of the workpiece surface and obtain a certain degree of cleanliness and different roughness.

Technical features:

1. Realize different reflection or matt.

2. It can clean the tiny burr on the surface of the workpiece, make the surface of the workpiece more flat, eliminate the harm of the burr, and improve the grade of the workpiece.

3. Clear the residual dirt left during pretreatment, improve the smoothness of the workpiece, make the workpiece show uniform metal color, and make the appearance of the workpiece more beautiful and beautiful.

9、 Polishing

Polishing: the polishing of the workpiece surface with flexible polishing tools and abrasive particles or other polishing media.

For different polishing processes: rough polishing (basic polishing process), intermediate polishing (finishing process) and fine polishing (polishing process), selecting the appropriate polishing wheel can achieve the best polishing effect and improve the polishing efficiency.

Technical features: improve the dimensional accuracy or geometric shape accuracy of the workpiece, obtain a smooth surface or mirror gloss, and also eliminate the gloss.

10、 Etching

Etching: commonly referred to as etching, also known as photochemical etching, refers to the removal of the protective film of the area to be etched after exposure and platemaking and development, and the contact with chemical solution during etching to achieve the effect of dissolution and corrosion, forming a concave-convex or hollow-out molding effect.

Exposure method: according to the drawing, the project will issue the size of material preparation - material preparation - material cleaning - drying → film pasting or coating → drying → exposure → development → drying - etching → film removal → OK

Screen printing method: cutting → cleaning plate (stainless steel and other metal materials) → screen printing → etching → film stripping → OK

Technical features:

advantage:

1. Fine machining of metal surface;

2. Give special effect to metal surface;Disadvantages: Most of the corrosive liquids (acid, alkali, etc.) used in etching are harmful to the environment.

Source: Metal surface treatment

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