Surface Treatment of Screws
Screws are one of the most commonly used fasteners in engineering components, household furniture and automotive applications, where they provide simple, efficient and secure fastening of components. A major factor influencing their performance is the type of surface treatment applied to them. This article examines the various surface treatments available for screws, the technologies used for their application, and the properties of the treated surfaces.
Surface treatment of screws includes various mechanical and chemical approaches. Mechanical processes involve applying treatments such as abrasives, tapping, grinding and shot peening. Chemical processes include galvanizing, nickel plating, anodizing and chemical passivation. Heat treatments and protective coatings are also used to improve the performance of screw surfaces.
Abrasive treatments typically involve the use of hand-held grinding wheels and sandpaper to grind away small amounts of the surface of the screw. This process can be used to remove minor defects, change the shape of the screw or improve the surface finish. The process is relatively economical and quick, though it is limited in what it can achieve.
Tapping is a process where a special tool is used to cut threads into the surface of the screw. The threads are then covered with a lubricant or special coating, such as a corrosion resistant coating, to provide better grip and prevent corrosion.
Grinding is a process where a grinding wheel is used to smooth and shape the surface of the screw. The process is relatively quick and inexpensive, but is limited in terms of what it can achieve.
Shot peening is a surface treatment process where small shots of metal are shot at high velocities onto the surface of the screw. This process creates a superficial layer of metal, which can improve the fatigue life and strength of the screw.
Galvanizing is a surface treatment process where a metal, usually zinc, is applied to the surface of the screw in order to protect against corrosion. The zinc coating acts as a sacrificial material, corroding away before the base metal, thus protecting the screw from corrosion and wear.
Nickel plating is a surface treatment process where a layer of nickel is applied to the surface of the screw. The nickel acts as a barrier to corrosion and creates a smoother surface, making it easier to work with.
Anodizing is a surface treatment process where a thin layer of aluminum oxide is applied to the surface of the screw. This process creates a hard, durable coating that is resistant to corrosion and wear.
Chemical passivation is a surface treatment process where a special solution is applied to the surface of the screw, resulting in a protective layer. This layer helps to prevent corrosion, as well as making the screw easier to work with.
Heat treatments are commonly used to improve the strength and hardness of screws, as well as to make them more resistant to wear, fatigue and corrosion. Heat treatment can be done through a variety of processes, including quenching, annealing, austempering and tempering.
Protective coatings, such as paint, are often applied to screws to provide additional protection against corrosion and wear. These coatings can also be used to improve the appearance of the screws.
In summary, there are a variety of surface treatments available for screws, including mechanical and chemical processes, as well as heat treatments and protective coatings. These processes can help to improve the performance and extend the life of screws in various applications.
