In the field of modern precision hardware manufacturing, the corrosion resistance and appearance quality of fasteners directly affect the service life and reliability of end products. Knurled lock nuts, made of brass, are widely used in industry due to their excellent physical and mechanical properties such as thermal conductivity, electrical conductivity, and rolling properties. However, brass is highly susceptible to oxidation and discoloration in the natural atmosphere, which places high demands on surface treatment processes. To effectively prevent rusting of these fasteners, the industry typically employs a combination of chemical polishing and passivation surface treatment methods for various knurled nuts to comprehensively improve their corrosion resistance and surface finish.
After the knurled lock nuts are machined, the surface often retains oxides, burrs, and various contaminants. Therefore, pretreatment with an environmentally friendly and universal brass chemical polishing solution is crucial. This polishing solution can quickly and gently remove surface impurities without causing excessive corrosion or pitting. In practice, immersion at room temperature for about 15 seconds is usually sufficient to restore the knurled brass nuts to a smooth luster, presenting a bright golden color and achieving a brand-new visual effect, laying a solid foundation for subsequent rust prevention treatment.
After chemical polishing and thorough cleaning, the workpiece must undergo rust prevention treatment to form a dense passivation film on the surface. The passivation process is relatively simple; just immerse the cleaned copper part in a dedicated copper passivation solution for about 15 minutes. The biggest advantage of this passivation process is that it does not change the original dimensions or appearance of the workpiece, nor does it affect its electrical conductivity. Therefore, for kelly insert nuts requiring high precision, this passivation treatment is an ideal choice for inter-process rust prevention and corrosion inhibition of the final product.
In addition to conventional chemical polishing and passivation processes, physical protection methods can be used to enhance rust prevention for some special applications. For example, some precision hardware companies design structures with protective sleeves that fit tightly against the top and periphery of the workpiece, effectively preventing moisture from seeping in through the threaded holes. This innovative moisture-proof design significantly improves the overall sealing and moisture-proof performance of kelly thumb nuts, which are frequently exposed to humid environments, extending their service life.
In industrial applications, the requirements for rust prevention processes vary depending on the fastener material. Compared to pure copper parts, some composite fasteners containing iron are more prone to electrochemical corrosion. Therefore, when treating kelly steel nuts, in addition to basic passivation rust prevention, phosphating, blackening, or electroplating processes are sometimes required to form a more robust protective film. For knurled cap nuts made of pure copper, the focus is on preserving their natural color and conductivity; passivation is undoubtedly the best solution, balancing aesthetics and protection.
Furthermore, storage environment and daily maintenance are crucial for preventing copper nuts from rusting. Brass products should be stored in a cool, dry, and temperature-controlled environment, with relative humidity ideally below 50%. When packaging, avoid using ordinary plastic bags that are not breathable and easily trap moisture; it is recommended to use anti-oxidation cloth, paper, or place silica gel desiccants inside. For complex knurled wing nuts, care should be taken to avoid contact with sulfur-containing rubber or acidic substances to prevent accelerated oxidation and discoloration.
Proper handling during fastener assembly and use can effectively slow down rusting. During installation, ensure hands are clean and dry to prevent chloride ions and lactic acid from sweat from forming fingerprint-like rust on the workpiece surface. For kelly bolted nuts that need to withstand high torque, it is recommended to use appropriate tools and apply the correct torque setting to prevent damage to the threads and disruption of the surface passivation film. Regularly inspecting and cleaning debris from the threads also effectively maintains their rust-resistant properties.
For fasteners requiring long-term storage or operating under harsh conditions, rust-preventive oil can be considered for supplementary protection. Depending on the duration of the rust prevention period, a thin-film or hard-film rust-preventive oil can be selected. In marine environments or high-salt-spray conditions, applying a hard-film rust-preventive oil to kelly bolted nuts provides longer-lasting protection. For short-term rust prevention between processes, easy-to-clean displacement-type rust-preventive oil can be used to ensure smooth subsequent machining.
If you have any technical questions regarding the surface treatment, rust prevention processes, or CNC machining of Plain Knurled Nut, please feel free to contact us. We will provide you with professional technical support and customized solutions.
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