Aluminum Die Casting : Surface Treatment Analysis

Aluminum die casting surface pretreatment in a variety of ways

Phosphating of Aluminum Materials

   Function of Accelerators and Additives

• Guanidine nitrate: It has the characteristics of good water solubility, low dosage, and rapid film formation, and is an effective accelerator for the phosphating of aluminum materials.

• Fluoride: It can promote film formation, increase film weight, and refine grains.

• Mn²⁺, Ni²⁺: They can significantly refine grains, make the phosphating film uniform and dense, and improve the appearance of the phosphating film.

• Zn²⁺: When the concentration is low, the film cannot be formed or is poorly formed. As the Zn²⁺ concentration increases, the film weight increases.

PO₄ content: It has a great influence on the phosphating film weight. Increasing the PO₄ content increases the phosphating film weight.




Research Methods




• Research is carried out by using methods such as SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction), potential-time curve, and film weight change to deeply understand the phosphating process and the characteristics of the phosphating film.

Physical Polishing - Magnetic Polishing

1. Principle

• The magnetic field is used to drive the magnetic polishing medium (such as steel needles) to perform high-frequency vibration and friction on the surface of the workpiece to remove surface irregularities and defects.

2. Advantages

• It can uniformly process the surface of the workpiece and achieve good polishing results even in hard-to-reach corners and gaps.

Alkaline Electrolytic Polishing Process

1. Research Results of Solution System

   
   

• The alkaline polishing solution system has been studied, and it has been found that corrosion inhibitors, viscosity agents, etc. have an impact on the polishing effect, and an alkaline solution system with good polishing effect has been successfully obtained.

• Additives that can reduce the operating temperature, extend the service life of the solution, and improve the polishing effect have been obtained for the first time. Experiments show that adding appropriate additives to the NaOH solution can produce good polishing results

  
  

2. Experimental Findings and Problems

   
   

• After DC constant voltage electrolytic polishing of the aluminum material surface with a glucose NaOH solution under certain conditions, the reflectivity can reach 90%, but there are still unstable factors in the experiment that need further research.

• The leveling effect of pulse electrolytic polishing can reach that of DC constant voltage electrolytic polishing, but the leveling speed is slower.

  
  

Other Methods

1. Environmentally Friendly Chemical Polishing of Aluminum and Aluminum Alloys

• The goal is to achieve zero emission of NOx and overcome the quality defects of previous similar technologies. The key is to add some compounds with special functions in the base liquid to replace nitric acid

  
  

2. Electrochemical Surface Strengthening Treatment of Aluminum and Its Alloys

   
   

• Anodic oxidation deposition forms a ceramic-like amorphous composite conversion film with a thickness of 5 - 10 μm and a microhardness of 300 - 540HV, and excellent corrosion resistance.

  
  

Selection of Surface Pretreatment Methods

Usually, physical polishing is adopted to simplify the process. It is efficient and environmentally friendly and can meet the surface treatment requirements of most aluminum die-casting products. Different methods can be selected according to the specific requirements of the product and production conditions to achieve the best surface treatment effect.

Aluminum Die Casting Surface Treatment Methods

Anodizing

Anodizing is a commonly used surface treatment method for aluminum die casting. Through this treatment, the corrosion resistance, wear resistance, and aesthetics of aluminum materials can be greatly enhanced. After anodizing treatment, a firm oxide film is formed on the surface of the extruded aluminum alloy profiles. This film has good stability in the atmosphere and can effectively prevent the product from corrosion. For example, daily aluminum pots, kettles, and washing machine inner drums all benefit from the good corrosion resistance brought by anodizing treatment. At the same time, the film layer obtained by anodizing has the characteristic of being able to adsorb a variety of organic dyes or inorganic pigments, so that various bright and vivid colors and patterns can be obtained on the oxide film, such as lighters, fountain pens, and handicrafts. It not only plays a decorative role but also serves as an anti-corrosion layer.

Electrophoretic Coating

The surface of the electrophoretic coating profiles has a soft luster and good corrosion resistance, and can resist the erosion of cement, mortar, and acid rain. This enables aluminum die-casting products to maintain good appearance and performance in various harsh environments. In practical applications, electrophoretic coating is often used for some products with high appearance requirements and that need to be used in complex environments, such as automotive parts and electronic product casings

Powder Electrostatic Spraying

The powder electrostatic spraying profiles have excellent corrosion resistance, and their resistance to acid, alkali, and salt spray is much better than that of oxidized and colored profiles. Through electrostatic action, the powder coating is evenly attached to the surface of the aluminum die-casting product, forming a firm protective film. This treatment method not only improves the corrosion resistance of the product but also can select powder coatings of various colors and textures according to different needs to meet the individual needs of different customers

Titanium Plating and Titanium Gold Plating Processes

The aluminum profile titanium gold plating process belongs to the coating technology and adds pre-plating and electroplating process steps on the basis of the conventional titanium plating process. The pre-plating process is to chemically treat the activated plated parts in an aqueous solution of salt and hydrochloric acid to produce a variety of colorful effects. This surface treatment method can add a unique appearance to aluminum die-casting products and make them more advantageous in terms of decoration. For example, some high-end home decorations and handicrafts often use titanium plating and titanium gold plating processes to enhance the grade and value of the products.

Wood Grain Transfer Printing

The vacuum wood grain lamination technology transfers the wood grain to the surface of the workpiece after electrostatic spraying of the metal product. This treatment method is not easy to fade, and the wood grain is realistic, which can greatly improve the product grade. Wood grain transfer printing is suitable for various decorative styles. Especially in the new Chinese decorative style, such as bungalows and Chinese villas, it can create a deep, retro, and solemn atmosphere. At the same time, as an ideal energy-saving and environmentally friendly material to replace traditional wood, the wood grain transfer printing product has no smell and zero pollution, and is an environmentally friendly green building material product.