What are the types of automotive fasteners? Which surface treatment is better for fasteners?
Do you know how many fasteners are in a car? There are approximately 3,000 to 4,000 fasteners. These small automotive fasteners are one of the critical components that connect the car body with various parts. Indeed, the quality of automotive fasteners significantly determines the lifespan and safety of a vehicle. In addition to introducing common types of fasteners, this article will also provide a detailed introduction to the surface treatment processes for automotive fasteners most highly regarded in the industry today.
What are the commonTypes of Automotive Fasteners?
As times change, automotive manufacturing technology continues to advance, and new vehicle models are constantly being introduced. Today, with the rise of Southeast Asia and other emerging markets, global demand for automotive fasteners has also grown. Although there are many car models, the most common types of fasteners include the following:
- Screws：Screws are among the most common fasteners, featuring a vast range of specifications and extremely broad applications. Common automotive screws include machine screws, security screws (anti-theft screws), and SEMS screws (assembly screws). Various internal vehicle components require screws made of different materials based on the functional requirements of the car manufacturer. For example, carbon steel screws, after undergoining heat treatment, achieve higher hardness, making them suitable for fastening applications in heavy-duty vehicle components.
- Nuts：Nuts, also known as screw nuts, are typically used in conjunction with bolts. They are essential when components require high-strength fastening. The most prominent applications for nuts are in a vehicle's chassis, wheel hubs, and suspension systems—areas that demand exceptionally secure connections to ensure the overall stability and safety of the vehicle.
- Washers：Washers, also known as "huasi" in some regions, are primarily used to distribute pressure, prevent loosening, or avoid scratching the surface of parts. They most commonly appear as a component of screw assemblies. Since fasteners within a vehicle can loosen or deform due to high vibrations, adding a washer can effectively distribute the pressure on the base.
- Rivets：Rivets are one-time fasteners commonly used in areas requiring permanent fixation. Automotive thin sheet metal parts often utilize riveting to tightly and permanently join two sheets of metal, reinforcing areas beyond welding to ensure the reliability of the overall structure.
- Specialized Customized Application Fasteners：With the diversification of vehicle designs, fastener manufacturers also customize automotive fasteners based on specific requirements. For example, off-road vehicles have particularly high performance requirements for components, so fasteners must undergo electroplating and coating to effectively increase resistance to high temperatures and corrosion.
Why must automotive fasteners undergosurface treatment？
一、Resistance to Environmental Factors
Automobiles are exposed to various environmental conditions for extended periods. Beyond rain, mud, sand, and gravel, even atmospheric humidity, temperature, and moisture are key factors that lead to the oxidation, rusting, or corrosion of metal fasteners. When fasteners undergo zinc plating or other surface treatments, a protective film is formed to effectively isolate oxygen and moisture, thereby significantly reducing the rate of corrosion.
二、Extending Service Life
If fasteners lack protection, their service life will be compromised even if the vehicle is not in an extreme environment. For example, the interior of a car engine is a high-temperature zone; if fasteners do not have a reinforced coating, the aging process will accelerate. Therefore, appropriate surface treatment not only protects the metal substrate but also significantly increases wear resistance and fatigue strength, while simultaneously reducing maintenance costs.
三、Enhancing Performance
Surface treatment enhances the fundamental performance of fasteners by improving their friction coefficient, tensile strength, and appearance quality. This ensures stability and precision during the assembly process.
What are the surface treatment methods for automotive fasteners?
| Surface Treatment Methods | Description |
| Electroplating | Electroplating utilizes the principle of electrolysis to attach metal ions from an electrolyte solution onto the surface of a fastener, forming a uniform thin film. Common types of electroplating includeZinc Plating、Zinc-Nickel Alloy PlatingNickel Plating, Chrome Plating, Copper Plating, andTin-Zinc Alloy Plating.Different plating materials result in various characteristic effects based on the specific treatment. |
| Phosphate Treatment | Also known as phosphating, this process is commonly used as a pre-treatment or a base for anti-rust coatings (priming) on automotive fasteners. By using spraying or immersion methods, a phosphate solution is attached to the surface of the fastener. Its primary functions are to provide adhesion and electrical insulation. |
| Anodic Oxidation (Anodizing) Through electrolytic passivation, an oxide film is added to the surfa | Through electrolytic passivation, an oxide film is added to the surface of metal fasteners. This is commonly applied to aluminum fasteners. Anodized aluminum alloy fasteners feature enhanced corrosion resistance and wear resistance. |
| Zinc-Flake Coating | Zinc-flake coating involves applying flake-shaped zinc and aluminum powders to the fastener surface through spraying or dip-coating, followed by high-temperature curing to form a protective film. Zinc-flake coating is particularly suitable for automotive fasteners that require high temperature and corrosion resistance. |
| Electrophoretic Coating | Electrophoretic coating is a KTL black topcoat used on zinc-flake basecoats, phosphating, or other metal substrates. It is applied directly onto the basecoat or untreated substrates (parts) through electrolytic coating technology. |
| Powder Coating | This process utilizes static electricity to attract metal powder coatings to the surface of the fastener. Compared to traditional liquid painting, it is more environmentally friendly and offers higher material utilization rates. |
Spring Profit | Automotive Fastener Surface Treatment Plant
Spring Profit provides top-tier expertise and services in three core processes—Electroplating,Phosphate Treatment, andZinc-Flake Coating—for major automotive manufacturers and fastener producers. With over 50 years of experience since our founding, we possess a profound understanding of industry demands and stay ahead of market trends. We consistently deliver outstanding performance in quality management, process stability, and product performance, while strictly complying with the rigorous specifications of all major global car manufacturers.
If you have any questions regarding surface treatments for automotive fasteners, please feel free tocontact us！