Fasteners are key components in mechanical equipment and building structures, and their performance directly affects the stability of the entire equipment or structure. Among them, corrosion resistance is one of the important indicators of fasteners. Surface treatment, as an important means to improve the corrosion resistance of fasteners, has been paid more and more attention. This paper will discuss the effect of surface treatment on the corrosion resistance of fasteners.
Definition and evaluation criteria for corrosion resistance of fasteners
The corrosion resistance of fasteners refers to their ability to resist corrosion under specific environmental conditions. According to the international standard ISO 1462 “Corrosion classification of metals and alloys”, the corrosion resistance of fasteners is mainly divided into four categories: full corrosion resistance, corrosion resistance, medium corrosion resistance and no corrosion resistance. The evaluation criteria mainly include corrosion rate, corrosion morphology, corrosion products and so on.
Influence of surface treatment on corrosion resistance of fasteners
The influence of surface treatment on the corrosion resistance of fasteners mainly includes electrochemical reaction, adsorption and physical erosion.
Electrochemical reaction: Surface treatment can change the electrochemical properties of the fastener surface and improve its resistance to corrosion. For example, coating the surface of a fastener with a layer of metal or alloy can cause it to form a galvanic cell in the corrosive medium, thus slowing the rate of corrosion.
Adsorption: Surface treatment can change the physical state of the surface of the fastener, thus affecting its adsorption of corrosive media. For example, the surface coating can prevent the contact between the corrosive medium and the surface of the fastener, reducing the corrosion rate.
Physical erosion: Some surface treatment methods can enhance the physical strength of the fastener surface and resist physical erosion. For example, surface heat treatment can increase the hardness of the fastener surface and reduce its risk of being worn or bruised, thereby indirectly improving its corrosion resistance.
Types and applications of surface treatments
Common surface treatment methods include coating, coating, printed circuit board, etc.
Plating: Plating is a method of coating a metal or alloy on the surface of a fastener to improve its corrosion resistance. For example, galvanized or chrome plating on the surface of the bolt can effectively improve its corrosion resistance. However, the coating may be damaged during machining or assembly, resulting in decreased corrosion resistance.
Coating: Coating is a method of applying a layer of organic or inorganic coating to the surface of a fastener to improve its corrosion resistance. For example, coating paint and epoxy resin on the surface of the bolt can effectively isolate the corrosive medium and improve its anti-corrosion performance. However, the coating may fall off or break under temperature, humidity and other environments, resulting in decreased corrosion resistance.
Printed circuit board: A printed circuit board is a method of making a printed circuit on the surface of a fastener, thereby improving its corrosion resistance. For example, making a printed circuit on the surface of a bolt can effectively improve its corrosion resistance. However, the printed circuit board may be subject to mechanical damage or chemical corrosion, resulting in decreased corrosion resistance.
conclusion
Surface treatment has a certain impact on the corrosion resistance of fasteners, but it is not a decisive factor. In the actual production and use process, attention should be paid to the selection of appropriate surface treatment methods and materials. At the same time, it is also necessary to comprehensively consider many factors such as machining, assembly, and use environment, so as to comprehensively improve the corrosion resistance of fasteners.
