Electroplated galvanized bolts vs color plated zinc bolts

Although electrogalvanized bolts and color-coated zinc bolts seem to be similar in appearance, there are obvious differences in their anti-corrosion performance and application scenarios. The electro galvanizing process forms a silver-white zinc layer on the surface of the bolt through electrolytic deposition. The thickness is usually between 5-12μm, and it can maintain rust-free for 80-120 hours in the salt spray test. This process is low-cost, and it only takes a few hours to process thousands of bolts in a single batch. The zinc layer has good conductivity and is suitable for structures that require current conduction, such as electrical cabinet grounding bolts or new energy battery pack connectors.

Color-coated zinc bolts are chromate passivated on the basis of electro galvanizing, and a rainbow-colored oxide film is formed on the surface. This 0.3-0.8μm film increases the salt spray tolerance to 200-300 hours, and gives the bolts a more distinctive appearance. For example, after the chassis bolts of automobiles are plated with color zinc, the service life can be extended from 2 years to 4 years in the high humidity environment of the coastal area, and the golden surface is convenient for quick identification of specifications and models during assembly. However, the passivation film will reduce the conductivity by about 25%, so it is not recommended for precision circuit connections.

In terms of cost, the processing fee of zinc plating is 15%-20% higher than that of ordinary electroplating due to multiple passivation processes. However, for structures exposed to the outdoors for a long time, such as 5G base station tower bolts, it is more economical to choose zinc plating – its maintenance cycle is extended from 18 months to 36 months, and the life cycle cost is reduced by more than 30%. The key parameters of the two processes are compared as follows:

Environmental factors are also driving process improvements. The chromium-containing solution used in traditional zinc plating is being replaced by safer alternatives. Although the new process has a slightly shorter rust prevention time, it is easier to treat wastewater and is more in line with international environmental standards. More and more electromechanical equipment bolts exported to Europe are now using chromium-free zinc plating.

In daily use, electroplated zinc bolts are suitable for dry environments such as furniture and indoor machinery, while zinc-plated bolts are mostly found in places such as automobile chassis and bridge steel frames that are exposed to wind and rain. When installing, it should be noted that the surface of zinc-plated bolts is smoother, and if the tightening force is too large, it is easy to damage the protective layer. It is usually recommended to use 5%-8% less force than ordinary electroplating. There is now a newly developed coating technology that can make zinc-plated bolts more rust-resistant and even used in the manufacture of precision instruments.


Post time: Apr-16-2025