Cold-rolled sheets and hot-rolled sheets in sheet metal processing materials are relatively insensitive to corrosion, and oxidation reactions are prone to occur. Moreover, the corrosion will continue to deepen during use, causing sheet metal processing parts to lose performance or scrap. Therefore, it is necessary to achieve the purpose of anti-corrosion and rust prevention by performing surface treatment on the sheet metal.

Several common surface treatment methods for sheet metal are: wire drawing, sandblasting, baking varnish, powder spraying, electroplating, anodizing, and silk screen printing. Because some sheet metal materials do not have the ability to prevent rust and corrosion, effective surface treatment is very necessary. One of the purposes of surface treatment of sheet metal parts can be to increase the service life of the product in harsh environments, and another purpose is to achieve a specific surface effect or function.

Then what are the main surface treatments in sheet metal fabrication? Next, JRPanel will focus on several surface treatment methods that occur frequently in the  fabrication process.

1. Wire Drawing 

 

Wire drawing is a method that uses the reciprocating motion of the wire drawing cloth to rub back and forth on the surface of the workpiece to improve the surface finish of the workpiece, and the surface texture is linear. It can improve the surface quality and conceal minor scratches on the surface.

According to the requirements of the drawing effect, the size and shape of different workpiece surfaces, we will choose different processing methods. Generally, there are two ways of wire drawing: manual wire drawing and mechanical wire drawing. Mechanical wire drawing also includes flat pressure type abrasive belt wire drawing, non-woven roller brush wire drawing, wide abrasive belt wire drawing and polishing machine wire drawing. Regarding these, we may explain in detail in future series.

The wire drawing process is the longest seen in household appliances panels, various digital product peripherals and panels, and notebook computer panels. It is also often used to make various signs, membrane switches and nameplates, etc.

2. Sandblasting

Sandblasting is a process of cleaning and roughening the surface of the substrate by the impact of high-speed sand flow.

Compressed air is used as power to form a high-speed jet beam to spray the spray material (copper ore, quartz sand, emery sand, iron sand, Hainan sand) at high speed to the surface of the workpiece to be treated, so that the appearance or shape of the outer surface of the workpiece surface is changed .

The mechanical properties of the workpiece are improved, so the fatigue resistance of the workpiece is improved, the adhesion between it and the coating is increased, and the durability of the coating film is prolonged. This will facilitate the leveling and decoration of the coating.

3. Paint Spraying

Paint spraying generally refers to liquid spray, which mainly includes two types: liquid baking paint and self-drying spray paint. Self-drying means that after spraying, it can be dried naturally at room temperature. The cost is lower, but the effect is incomparable with baking varnish. The color effect of spray paint will be better, the thickness of the paint film is relatively thin, suitable for some precision products, and the cost is higher. Common materials for this surface treatment process: cold-rolled sheet, hot-rolled sheet, etc.

4. Powder Coating

Powder coating treatment means that the powder is polarized and adheres evenly to the surface of the product with the opposite polarity under the action of the electric field force. Plastic spraying can make the workpiece wear-resistant and increase the corrosion resistance. It is suitable for relatively coarse products such as cabinets and equipment. The cost is lower, and the plastic powder can also be recycled.

As for powder coatings, they are generally made by mixing special resins, pigments, fillers, and curing agents in a certain proportion, and then through processes such as hot extrusion, crushing, and sieving. 

5. Electroplating

Electroplating is the process of plating a thin layer of other metals or alloys on the surface of certain metals using the principle of electrolysis, thereby preventing metal oxidation, improving wear resistance, conductivity, light reflection, corrosion resistance and enhancing aesthetics. 

Electroplating is divided into rack plating, barrel plating, continuous plating and brush plating, which are mainly related to the size and batch of parts to be plated. Rack plating is suitable for products of general size, such as car bumpers, bicycle handlebars, etc. Barrel plating is suitable for small parts, fasteners, washers, pins, etc. Continuous plating is suitable for batch production of wires and strips. Brush plating is suitable for partial plating or repair.

6. Anodic Oxidation

Anodizing technology is the most widely used and most successful alloy surface treatment technology. 

Anodizing generally refers to the process in which aluminum and its alloys form an oxide film on aluminum products (anode) due to the effect of an external current under the corresponding electrolyte and specific process conditions.

In the actual process, anodic oxidation is more aimed at aluminum alloys, which can be applied in daily life. Because of the characteristics of this process, a hard protective layer is produced on the surface of aluminum parts, which can be used to produce daily necessities such as kitchen utensils.

7. Silkscreen

I believe everyone is already familiar with the surface treatment method of silk screen printing. Specifically, it refers to the process of screen printing various logos on the surface of the material. The main principle is the same as the principle of film imaging, and it is also an exposure process. Flat screen printing is mainly used on general planes. But if you encounter a place with a deep pit, you need to use pad printing.

8. Dip Coating

The product is immersed in the molten material and heated, and the heated metal combines with the surrounding molten material to form a surface material with a certain thickness. According to the different raw materials used for dipping, it can be divided into liquid dipping and powder dipping. The hangers we use to dry clothes, the pliers, the rubber sleeves on the scissors, and the wrenches of the water valve all use this process.

Metal dip coating is a new type of technical treatment process for anti-corrosion of metal surfaces. It is a heating process. The metal is preheated, dipped and solidified. During dipping, the heated metal sticks to the surrounding materials. The hotter the metal, the longer the dipping time and the thicker the material used.

Other surface treatment methods, such as baking varnish, enamel, etc., are not commonly used for chassis and cabinet sheet metal fabrication products, so we will not introduce them here. If you have any questions about sheet metal fabrication, don't hesitate to contact us!