Surface treatment is to form a surface layer with one or more special properties on the surface of zinc alloy die castings by physical or chemical methods. Surface treatment can improve product appearance, texture, function, and other aspects of performance.
Anodizing :
It is mainly the anodization of aluminum alloy die castings, and zinc alloy die castings cannot be done temporarily due to technical reasons. It uses the principle of electrochemistry to form a layer of Al2O3 (aluminum oxide) film on the surface of aluminum alloy die castings. This layer of oxide film has special properties such as protection, decoration, insulation, and wear resistance.
Monochrome, gradient color: polishing/sandblasting/drawing→degreasing→anodizing→neutralizing→dyeing→sealing→drying
Two-color:
①Polishing/sandblasting/drawing→degreasing→masking→anodizing 1→anodizing 2→sealing→drying
②Polishing / sandblasting / wire drawing → degreasing → anodizing 1 → laser engraving → anodizing 2 → sealing → drying
Technical Features:
1. boost strength
2. Achieve any color except white
3. Realize nickel-free sealing to meet the requirements of European, American, 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, and the key to improving the yield of oxidation lies in the appropriate amount of oxidant, suitable temperature and current density, which requires the aluminum alloy die-casting factory to continuously explore and seek breakthroughs in the production process.
Electrophoresis :
Used for stainless steel, aluminum alloy die castings, zinc alloy die castings, etc., it can make the products show various colors, maintain the metallic luster, and at the same time enhance the surface properties and have good anti-corrosion properties.
Process flow: pretreatment→electrophoresis→drying
advantage:
1. rich in color;
2. No metal texture can cooperate with sandblasting, polishing, wire drawing, etc.;
3. Processing in a liquid environment can achieve surface treatment of complex structures;
4. The technology is mature and can be mass-produced. Disadvantages: The ability to cover up defects is average, and the electrophoresis of die castings requires higher pretreatment.
Micro-arc oxidation :
The process of applying a high voltage in an electrolyte solution (usually a weak alkaline solution) to generate a ceramic surface film layer, which is the result of the synergistic effect of physical discharge and electrochemical oxidation.
Process flow: pretreatment→hot water washing→MAO→drying
advantage:
1. Ceramic texture, dull appearance, no high-gloss products, delicate touch, 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 and weather resistance, and has good heat dissipation performance. Disadvantages: At present, the color is limited, only black and gray are more mature, and bright colors are currently difficult to achieve; the cost is mainly affected by high power consumption, and it is one of the highest costs in surface treatment.
PVD vacuum plating
The full name is physical vapor deposition, which is an industrial manufacturing process. It is a technology that mainly uses physical processes to deposit thin films. Various zinc alloy die castings and aluminum alloy die castings can use the vacuum electroplating process.
Process flow: cleaning before PVD → vacuuming in the furnace → target washing and ion cleaning → coating → end of coating, cooling out of the furnace → post-processing (polishing, AFP)
Technical features: PVD (Physical Vapor Deposition, Physical Vapor Deposition) can coat the metal surface with high hard plating and high wear resistance cermet decorative coating Five, electroplating is the process of attaching a layer of the metal film to the surface of the metal by electrolysis. It is a technology that can prevent corrosion, improve wear resistance, electrical conductivity, reflectivity, and enhance aesthetics. Electroplating technology is widely used and can be applied to many zinc alloy die castings and aluminum alloy die castings. Process flow: pretreatment → cyanide-free alkali copper → cyanide-free cupronickel tin → chrome plating
advantage:
1. The coating has a high gloss and high-quality metal appearance;
2. The base material is SUS, Al, Zn, Mg, etc.; the cost is lower than PVD.
Disadvantages: poor environmental protection and high risk of environmental pollution.
Powder coating :
Powder coating is sprayed on the surface of zinc alloy die-casting and aluminum alloy die-casting by powder spraying equipment (electrostatic spraying machine). The powder coating is cured by high-temperature baking and leveling and becomes the final coating with various effects (different kinds of effects of powder coatings).
Technological process: upper part→electrostatic dust removal→spraying→low temperature leveling→baking
advantage:
1. Rich colors, high gloss, matte optional;
2. Low cost, suitable for building furniture products and shells of heat sinks, etc.;
3. High utilization rate, 100% utilization, environmental protection;
4. Strong ability to conceal defects;
5. Can imitate wood grain effect.
Disadvantages: Currently used in electronic products less.
brushed metal
It is a surface treatment method that forms lines on the surface of zinc alloy die castings by grinding products to achieve decorative effects. According to the different lines after drawing, it can be divided into straight-line drawing, random pattern drawing, corrugated patterns, or swirl patterns.
Technical features: The wire drawing treatment can make the metal surface obtain a non-mirror-like metallic luster, and the wire drawing treatment can also eliminate the subtle defects on the surface of the zinc alloy die casting.
sandblasting
It uses compressed air as the power to form a high-speed spray beam to spray the spray material on the surface of the zinc alloy die-casting to be treated at a high speed so that the appearance or shape of the outer surface of the zinc alloy die-casting surface changes, and a certain degree of cleanliness and different A process of roughness.
Technical Features:
1. To achieve different reflective or matt.
2. It can clean the tiny burrs on the surface of zinc alloy die castings, make the surface of zinc alloy die castings more flat, eliminate the harm of burrs, and improve the grade of zinc alloy die castings.
3. Clear the residue left in the pretreatment, improve the finish of the zinc alloy die-casting, make the zinc alloy die-casting reveal a uniform metal color, and make the zinc alloy die-casting appearance more beautiful and good-looking.
polishing
Modification of zinc alloy die-casting surfaces using flexible polishing tools and abrasive particles or other polishing media. For different polishing processes: rough polishing (basic polishing process), medium polishing (finishing process), and fine polishing (glazing process), selecting the appropriate polishing wheel can achieve the best polishing effect and improve the polishing efficiency at the same time.
Technical features: Improve the dimensional accuracy or geometric shape accuracy of zinc alloy die castings, obtain smooth surface or mirror gloss, and also eliminate gloss.
etching
Usually referred to as etching, also known as photochemical etching, it refers to the removal of the protective film in the area to be etched after exposure to plate making and development, and contact with the chemical solution during etching to achieve the effect of dissolution and corrosion, forming concave-convex or hollow molding effect.
Exposure method: The project prepares the size of the material according to the graphics → material preparation → material cleaning → drying → film or coating → drying → exposure → development → drying-etching → stripping → OK.
Screen printing method: cutting material → cleaning plate (stainless steel and other metal materials) → screen printing → etching → stripping → OK
advantage:
1. The surface of zinc alloy die casting can be finely processed;
2. Give special effects to the surface of zinc alloy die castings; Disadvantages: Most of the corrosive liquids (acid, alkali, etc.) used in etching are harmful to the environment.
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