Fastener surface treatment process: galvanizing, phosphating, blackening, which one should I choose?

In modern industry, fasteners are key elements for connecting parts, and their performance directly affects the stability and safety of the entire equipment. The surface treatment of fasteners is not only related to their beautiful appearance, but also to their anti-corrosion performance and service life. Therefore, choosing a suitable surface treatment process has become an important part of fastener manufacturing that cannot be ignored.

First, let's talk about the most commonly used electrogalvanizing. Electrogalvanizing has become a common coating for commercial fasteners with its relatively low cost and good appearance. However, its anti-corrosion performance is not outstanding, especially in high humidity or corrosive environments, and its durability needs to be improved. In order to solve this problem, some special sealers have been introduced to extend its anti-corrosion life. But the cost of such treatment has also increased, and it needs to be weighed according to the specific usage scenario.

Next is phosphating. Phosphating is not only affordable, but also has good corrosion resistance and wear resistance, especially suitable for high-strength bolts. Oiling after phosphating can further improve its anti-corrosion performance and is suitable for the connection of important parts. It is worth mentioning that phosphating can also effectively avoid hydrogen embrittlement, which is a factor that must be considered in the manufacture of high-strength bolts.

Let's talk about oxidation (blackening) treatment. This treatment method is extremely low-cost, but it will rust quickly in the absence of oil. Therefore, it is usually combined with oiling to extend the service life. Although the corrosion resistance is limited, it is still an economical choice in some cost-sensitive occasions.

Cadmium electroplating performs well in marine atmospheric environments due to its excellent corrosion resistance. However, the high cost and waste liquid treatment costs during the processing process limit its application range. Chromium electroplating is known for its high hardness and wear resistance, but it also has high costs and hydrogen embrittlement problems.

Nickel plating is a surface treatment method that can both prevent corrosion and maintain good conductivity. It is mainly used in occasions where both corrosion resistance and conductivity are required, such as the lead-out terminals of vehicle batteries.

Hot-dip galvanizing and Zinc infiltration are two surface treatment methods widely used in engineering. Hot-dip galvanizing is known for its thicker coating and good corrosion resistance, but it may cause problems with difficulty in screwing internal and external threads. Zinc infiltration is favored for its good uniformity, high bonding strength with the substrate, and environmental protection and pollution-free.

Finally, we have to mention Dacromet treatment. This new type of anti-corrosion coating not only has excellent anti-corrosion performance, but also has no hydrogen embrittlement problem and good torque-preload consistency. However, it is expensive and has environmental problems, so it needs to be used after comprehensive consideration of cost and environmental requirements.

In summary, the choice of fastener surface treatment needs to comprehensively consider multiple factors such as anti-corrosion performance, cost, use environment, environmental requirements, and the performance requirements of the fastener itself. Only by finding the most suitable surface treatment method can we ensure that the fastener maintains stable performance and reliable safety in long-term use.

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