Tocqueville once said that opportunities would be useless if there was no prior preparation. For the electroplating process, it is also very important to prepare well in advance. The surface treatment of the base material directly affects the quality of the coating. Therefore, before the substrate material is electroplated, the surface treatment of the substrate or the surface of the part must be carefully performed to improve the bonding between the coating and the substrate. In order to ensure that the coating meets the quality requirements.
In general, qualified plating products have the following requirements:
1. The coating structure is compact, the surface is smooth and flat, and some even require a certain brightness;
2. The thickness of the coating should be uniform on different parts of the substrate, or the difference of the thickness of the coating on each surface of the substrate should be as small as possible;
3. The bond between the coating and the base material must be firm, and it is not allowed to cause peeling and bubbling of the coating.
In order to meet the above three requirements, the following four factors should be noted in the preparation work before electroplating.
1. The essence of the matrix material
The variety, structure, molding method, processing history and other aspects of the substrate are closely related to the selection of the plating solution and the process plan. Different materials, casting, forging, hot rolling or cold rolling, different heat treatment and other different molding methods and parts made by different processing techniques, preparation work is not the same. For important parts, the process plan must also be considered in the environment it has experienced and the history of processing or work.
2, the degree of cleanliness
The surface of the processed parts may have processing debris, oily impurities, scale or oxide film, oil layer after heat treatment, various substances adhering, and wax, thick oil seal oil layer, thin layer. Different pollutants such as rust preventive oil film and corrosion inhibitor need to be treated in different ways. For example, thick grease and thin oil film must be cleaned at different levels.
3. Surface structure and state
The surface structure of the substrate to be plated directly affects the structure and characteristics of the coating. The rough surface has a high porosity and is prone to underplating, and the rough inner hole is difficult to cover. Situations like this are taken into consideration when arranging construction. The unchanging process does not adapt to a variety of surfaces, otherwise the quality of the products produced will be uneven. Therefore, the electroplating factory needs to perform the electroplating process on the substrate according to local conditions.
4. Corrosion, size, quantity and precision of the parts and materials
Some materials are susceptible to corrosion, such as aluminum, magnesium, zinc, etc.; some will dissolve in the anode treatment, such as chromium, tin, etc.; and porous such as powder metallurgy products and joints or assemblies with gaps, all have to be different Measures to deal with. Parts that are large, small, small, and particularly complex in shape or extremely precise in size must be considered in the appropriate process.
It can be seen that the importance of pre-treatment preparation of the surface of the metal matrix material before electroplating is undoubted. Due to the wide variety of matrix materials, the processing process and the storage environment are also different, so that the surface states of various substrates before plating are very different. Big. In addition, the composition, operating conditions, and plating methods of various plating layers are also greatly different. Therefore, the preparation work before plating of the base material must be properly carried out according to the specific situation.