Brief introduction: surface treatment technology of metal stamping products after processing

Brief introduction of surface treatment technology of metal stamping products after processing

After metal stamping products are formed, oil stains and burrs are easy to remain on the surface, and bare materials are easy to corrode and wear in the use environment, which affects the service life and appearance texture. Surface treatment, as the key follow-up process of metal stamping, can modify the surface of products by chemical, physical or electrochemical methods, which can not only improve the core properties such as corrosion resistance, wear resistance and conductivity, but also optimize the appearance value to meet the needs of different application scenarios. The following briefly introduces the common surface treatment processes, characteristics and applicable scenarios of metal stamping products, covering mainstream technologies and core application logic:

A, basic protective surface treatment process

The basic protection technology focuses on improving the anti-corrosion and anti-rust ability of products, which is suitable for all kinds of general metal stamping parts and is the most widely used surface treatment type.

Electroplating process: metal coating is deposited on the surface of products by electrolysis. Common coatings include zinc plating, nickel plating, chromium plating and copper plating. The cost of zinc plating process is low, which can be divided into hot dip galvanizing and electro-galvanizing. The thickness of zinc plating layer is usually 5-20μm, and the salt spray test can reach 48-1000 hours, which is suitable for outdoor hardware, home appliance stamping parts and so on. Nickel plating layer has high hardness, good wear resistance and certain decoration, which is suitable for stamping parts in precision instruments and electronic equipment. Chromium plating layer has high gloss, excellent corrosion resistance and wear resistance, but its cost is high, and it is mostly used in high-end hardware tools, automobile parts and so on. The electroplating process needs to strictly control the concentration, current density and temperature of electroplating solution to ensure that the coating is uniform, bubble-free and shedding-free.

Passivation treatment: mainly for stainless steel, galvanized parts, etc., a dense oxide film is formed on the surface of the products by chemical method to enhance the antirust ability. Nitric acid or chromate solution is commonly used for passivation of stainless steel. After treatment, the surface is grayish white, which does not affect the dimensional accuracy of products. It is suitable for stamping parts in medical devices and food machinery. Passivation of galvanized parts can further improve the salt spray corrosion resistance and prolong the service life, and the passivation process is simple in operation and low in cost, which is suitable for mass production.

Phosphating treatment: the product is immersed in phosphating solution to form a phosphate conversion film on the surface. This film has good adsorption and is often used for pretreatment before painting, which can improve the bonding force between the paint film and the substrate and has certain rust prevention ability. Phosphating process is divided into normal temperature phosphating, low temperature phosphating and high temperature phosphating, which is suitable for stamping parts that need subsequent coating, such as automobile body and construction machinery. After treatment, it needs to be dried in time to prevent the film from falling off due to moisture.

Second, the decorative and functional composite surface treatment process

This kind of technology gives consideration to both protective performance and decorative appearance, and some of them also have special functions, which are suitable for scenes with dual requirements for face value and performance.

Electrophoretic coating: coating particles are deposited on the surface of the product by electric field to form a uniform and smooth paint film. The electrophoretic paint film has the advantages of uniform thickness (usually 10-30μm), strong adhesion, excellent corrosion resistance, high coating utilization rate and good environmental protection. According to the color of paint film, it can be divided into black, gray and other color systems. It is suitable for stamping parts such as automobile parts, furniture hardware and electronic equipment shells, and can meet the decorative needs of different customers.

Spraying process: including powder spraying and liquid spraying. Powder spraying adheres powder coating to the surface of the product evenly through electrostatic adsorption, and forms a paint film after high-temperature curing. It has the characteristics of thick paint film (20-100μm), strong impact resistance, wear resistance and weather resistance, and rich color selection, and is suitable for outdoor hardware, architectural decorative stamping parts, etc. Liquid spraying uses a spray gun to atomize liquid paint and spray it on the surface. The paint film is fine and high in gloss, and it is suitable for household appliance shells, consumer electronics accessories, etc. However, the utilization rate of the paint is relatively low, and environmental protection should be done.

Anodizing: It is mainly suitable for aluminum and aluminum alloy stamping parts. An oxide film is formed on the surface by electrolysis. The thickness of the oxide film can be controlled at 5-20μm, which has good wear resistance, corrosion resistance and insulation. After anodizing, a variety of colors (such as black, red, blue, etc.) can be achieved by dyeing process, and the decorative effect is good. It is suitable for mobile phone housings, medical devices, aerospace parts, etc., and the hardness of the film can be adjusted according to requirements to meet the use requirements of different scenes.

Three, special functional surface treatment process

According to the requirements of specific use scenarios, this kind of technology endows stamping products with special functions such as conductivity, heat conduction and lubrication, and is mostly used in precision machinery, electronic appliances and other fields.

Conductive treatment: including gold plating, silver plating, tin plating, etc. The gold plating layer has excellent conductivity, low contact resistance and strong corrosion resistance, and is suitable for stamping parts such as precision electronic connectors and relays. Silver plating layer has good electrical and thermal conductivity, but it is easy to oxidize, and is often used in high-frequency electronic components. Tin plating layer has good weldability and conductivity, which is suitable for stamping parts such as wire terminals and circuit boards, and can ensure the stability of electrical connection.

Lubrication treatment: By coating lubrication film (such as PTFE coating and MoS2 coating) on the surface of products, the friction coefficient is reduced, and the wear resistance and service life of products are improved. It is suitable for stamping parts (such as gears and sliders) in mechanical transmission, which can reduce the wear and energy loss during movement.

Blackening treatment: Also known as bluing treatment, a black oxide film is formed on the surface of steel products through high-temperature oxidation or chemical oxidation, which is mainly used for rust prevention and beauty. The treatment process is simple and the cost is low. It is suitable for stamping parts such as tools, springs and fasteners, but the film layer is thin and the protective performance is limited, so it is mostly used in indoor environment.

Four, the principle of surface treatment process selection

When selecting the surface treatment technology of metal stamping products, it is necessary to comprehensively consider the use environment (such as outdoor, indoor, humid environment, etc.), performance requirements (corrosion resistance, wear resistance, conductivity, etc.), appearance requirements and cost budget. For example, the stamping parts used outdoors are given priority to the processes with strong weather resistance such as zinc plating and powder spraying; Gold plating, silver plating and other processes with excellent conductivity are preferred for precision electronic components; For consumer goods with high appearance requirements, anodic oxidation, electrophoretic coating and other processes can be selected. At the same time, it is necessary to strictly follow the environmental protection standards and give priority to the selection of low-pollution and low-energy processes to ensure that the production process meets the national environmental protection requirements.

In a word, there are many kinds of surface treatment processes for metal stamping products, and different processes have their own advantages and disadvantages, which need to be selected reasonably according to actual needs. Scientific surface treatment can not only make up the surface defects after stamping, but also significantly improve the comprehensive performance and added value of products, prolong their service life and meet the application needs of different industries.