Fastener coatings, such as galvanizing or other coatings, help prevent corrosion by forming a protective covering. This covering can effectively isolate the fastener from the external environment and prevent oxygen, moisture or other corrosive substances from directly contacting the metal parts of the fastener, thereby slowing or stopping the corrosion process. Specifically, the ways in which fastener coatings prevent corrosion include:
Electroplating and hot-dip galvanizing: Both methods cover the surface of the fastener with a layer of metal, such as zinc. Electroplating is the process of coating the surface of the fastener with a metal film through the principle of electrolysis, while hot-dip galvanizing is the process of immersing the fastener in molten zinc to form a layer of zinc on the surface. These methods can effectively improve the corrosion resistance and oxidation resistance of fasteners.
Chromizing or passivation: This is a process in which a chromate or passivation coating is formed during post-treatment by a solution containing chromium compounds. This can increase corrosion resistance and prevent the coating from darkening or fading.
Powder sherardizing: This is a coating formed by a zinc-iron diffusion reaction, with the main component being delta phase (FeZn17). This coating has good corrosion resistance and wear resistance, which is comparable to the corrosion resistance of hot-dip galvanizing layer .
Dacromet treatment: This is an environmentally friendly surface treatment technology that does not contain heavy metals and has good corrosion resistance and torque-preload consistency. It prevents corrosion by forming a protective film on the surface of the fastener.
These coating treatment methods have their own characteristics, and the choice of which method depends on the specific application environment and performance requirements. For example, electroplating has a lower cost and is suitable for occasions with high aesthetic requirements; while hot-dip galvanizing is suitable for environments with extremely high corrosion resistance requirements. Chrome or passivation, powder sherardizing and Dacromet treatment provide additional corrosion resistance and environmental performance .