Surface Treatment for Machined Parts
To prevent corrosion or simply enhance the appearance, engineers often specify additional finishing processes for the external surfaces of CNC precision components after metal part machining or manufacturing.
Furthermore, some of these treatments also provide enhanced mechanical or electrical properties, contributing to the overall functionality of the components.
1. Improving Product Precision: After machining, some products may have rough surfaces and residual stresses, which can reduce product precision and affect the dimensional accuracy of component fit. In such cases, surface treatment is necessary to improve the surface quality of the product.
2. Enhancing Wear Resistance: If components are intended to interact with other parts during normal use, prolonged usage can lead to increased wear. In such situations, surface treatment is required to prolong the lifespan of the components.
3. Improving Corrosion Resistance: Components that are exposed to highly corrosive environments for extended periods require special surface treatments, such as polishing, coating, or anti-corrosive materials. These treatments enhance corrosion resistance and extend the product's lifespan.
Regardless of the reason, each of the following eight metal surface finishing processes plays an important role in the manufacturing process:
1. Anodizing
Anodizing is an electrolytic passivation process used to increase the thickness of the naturally occurring oxide layer on the surface of aluminum components. Aluminum parts act as anodes (hence the term "anodizing"), and a current passes between them and a cathode (typically a flat aluminum rod) through an electrolyte solution (most commonly sulfuric acid). The main functions of anodizing are to enhance corrosion resistance, wear resistance, and adhesion to paints and primers.
2. Metal Plating
Metal plating is a technique where a chemical bath is used to coat or alter the surface of a substrate with a thin layer of metal (such as PTFE or nickel). Electroplating employs an electrical current to deposit the metal onto the substrate, while electroless plating uses autocatalytic practices where the substrate acts as a catalyst in the reaction. It offers numerous advantages such as improved durability, corrosion resistance, surface friction, and appearance. Additionally, it serves as a useful option for coating other metals.
3. Chemical Deposition
This process involves applying a uniform metal layer onto a substrate without the need for electrical charge. Nickel is commonly used in this process as it provides uniform thickness even on irregularly shaped objects. Chemical deposition is an important process for improving corrosion resistance, oxidation resistance, and wear resistance.
4. Passivation
Passivation is a process used to improve the surface condition of stainless steel by dissolving embedded iron from forming, machining, or other manufacturing steps. This is achieved by immersing stainless steel in an acid solution to dissolve the residual iron and form a thin oxide layer on the surface. It enhances corrosion resistance and maintains the dimensional integrity of tight-tolerance parts.
5. Powder Coating
Powder coating involves melting dry plastic powder onto metal to create a textured, matte, or glossy coating. The powder is electrostatically applied to the metal and then heated to cure, allowing it to flow and form a hard "skin."
6. Hot Blackening
This is a process that involves applying a thin layer of black oxide onto the surface of a product using machinery to create a highly wear-resistant matte black finish. Hot blackening is a high-temperature process where the product is inserted into a series of tanks containing corrosive agents, cleaning agents, and cooling agents.
Fujian Meta Technology Co., Ltd is a machining factory with over a decade of experience in CNC machining, equipped with comprehensive CNC turning, milling, grinding, drilling, and processing capabilities. We welcome inquiries from partners with machining needs to contact us for a quotation.