Fasteners are used to join two or more objects together and they are often subjected to harsh environments, such as exposure to moisture, salt, and chemicals. To prevent corrosion and increase their durability, fasteners are often coated with various surface treatments. Here are some common types of surface coatings for fasteners:
- Zinc coatings: Zinc is a common coating material for fasteners because it is inexpensive and provides good corrosion resistance. Zinc coatings can be either electroplated or hot-dipped. Electroplated coatings are thin and provide only limited corrosion resistance, while hot-dipped coatings are thicker and provide better protection.
- Cadmium coatings: Cadmium is another coating material used for fasteners, especially in aerospace and military applications. Cadmium provides excellent corrosion resistance, but it is toxic and its use is being phased out due to environmental concerns.
- Nickel coatings: Nickel is used for fasteners that require high corrosion resistance and also for decorative purposes. Nickel coatings can be electroplated or applied using electroless plating.
- Chromium coatings: Chromium is used for fasteners that require very high corrosion resistance, such as those used in marine environments. Chromium coatings can be electroplated or applied using physical vapor deposition (PVD) or chemical vapor deposition (CVD).
- Organic coatings: Organic coatings, such as paint or powder coating, can be applied to fasteners to provide a decorative finish and to protect against corrosion. Organic coatings are not as durable as metallic coatings, but they are often used for fasteners that are not exposed to harsh environments.
It's important to select the appropriate coating material and thickness based on the specific application and the expected operating conditions to ensure the fasteners will perform as expected. We normally use salt-spary test(SST) and kesternich test to inspection/request your need of surface coating.