Enhance usabiltiy and improve performance
Fasteners are sometimes coated or plated with an added layer of a metal, polymer, or other substrate to enhance usability. These coatings can help reduce friction, improve corrosion resistance, improve anti-seize performance, or add other functionality to the fastener surface. Below are some of the more common coatings and platings that Extreme Bolt can offer.
Often referred to as “blackening”, black oxide coated bolts undergo a chemical treatment that adds a layer of protection against corrosion and abrasion. There are a few processes that can be used to produce a black oxide coated bolt: hot bath, mid-temperature bath, or cold coated. Black oxide coatings are typically used on steel, alloy steel, stainless steel, copper, and zinc bolts.
• ASTM D769
• AMS 2485
Like Zinc plating, cadmium adds an extra layer of protection to bolts made of steel, brass, and aluminum. Cadmium coatings help protect the bolt from saltwater and alkaline environments, as well as mold and bacteria growth. Bolts plated in cadmium have a reduced chance of galvanic corrosion as well, which is caused by the electrical reaction of dissimilar metals in an aqueous environment.
Cadmium plated bolts also have a natural lubricity which can be helpful in preventing galling and friction. This makes it an ideal solution for bolts that must be repeatedly changed, as well as fasteners used in moving parts.
In addition, cadmium plated bolts provide low electrical resistance and excellent electrical conductivity.
• ASTM 766, ASTM A165, ASTM B766
• AMS 2400, AMS 2401
Electroplating chromium to a bolt can increase its life span by minimizing wear on the base metal. Since the chromium layer will increase the surface hardness, it can extend the life of a bolt up to 10 times depending on the base material and specific conditions. Chromium’s hard layer also helps to improve corrosion and abrasion resistance. In addition, chromium plated bolts have a lower coefficient of friction which helps to prevent galling. The chrome plating is also non-magnetic.
The main disadvantage of chrome plated bolts is the high cost. As it is typically applied to stainless steel, often a specialty alloy can offer exponentially better corrosion resistance at a similar price point and will be much more robust. Corrosion resistant alloys that are often considered are nickel alloys like Hastelloy, Inconel, Duplex, and Monel, as well as titanium.
• MS 2460, AMS 2406
• ASTM B 177
Dry Film Lubricant
Dry film lubricants are used in many environments – heat and low temperatures, high and low pressure, chemical and corrosive acids, and high purity. They help minimize friction and prevent seizing and galling in applications where oils and liquid lubricants cannot be used. There are many options when it comes to dry film lubricants.
Benefits of Dry Film Lubricants
• Corrosion and chemical resistance
• Low friction
• Galling and fretting resistance
• High temperature protection
• Wear and abrasion resistance
• Noise reduction
Types of Dry Film Lubricants
Coatings like PTFE/Teflon can be applied to a metal bolt in order to provide a hard, slick finish. Fluoropolymer coatings are ideal for preventing friction in hot, cold, and corrosive chemical environments. PTFE is an ideal dry lube coating since it is virtually inert to most chemicals and is considered the slickest (smooth) material in existence.
This dry film coating offers a combination of both fluoropolymers and organic polymers for both strength and low friction. In addition to a solely fluoropolymer coating, Xylan also offers excellent wear resistance.
- Molybdenum disulfide
Usable from -65°F (-54°C) to 2400°F (1316°C), Extreme Anti-Seize lubricant – a patented moly disulfide lubricant prevents seizure, heat-freeze and galling, lowers friction, and minimizes bolt breakage. Moly disulfide is not affected by contraction, expansion or vibration and works in corrosion environments, as well as a broad temperature range.
Though graphite coatings exhibit both metallic and a non-metallic properties, it is the non-metallic characteristics such as inertness, high thermal resistance, and lubricity make graphite an ideal lubricant coating.
Nickel plated bolts benefit from not only improved corrosion protection, but also heat, erosion, and wear resistance. This coating also provides excellent lubricity. Nickel plated fasteners also have excellent adhesion properties, which makes it an ideal base layer for addition coatings such as chromium.
Nickel plated bolts can be produced by electroplating or electroless plating. Electroless plating is a process used to chemically deposit the nickel coating. This is excellent for components with complex designs or sharp edges as it provides a very uniform coating deposit. Electroplated nickel bolts offer precise plating thickness to exact tolerances.
Electroless Nickel Plating Specifications
• AMS-C-26074, AMS 2403, AMS 2404, AMS 2405, AMS 2423, AMS 2424
• QQ-N-290, QQ-N-290
Electrolytic (Electro) Plating Specifications
• AMS 2403, AMS 2423, AMS 2424,
• QQ-N-290, QQ-N-290
Nickel-PTFE coated bolts go through an electroless nickel process combined with PTFE particles. The result is a coating of 20-30% PTFE. This coating is excellent for preventing sticking, galling, friction, and drag for bolts used on machinery with moving parts. Nickel-PTFE coated screws are unique because this coating combines the self-lubricating properties of PTFE with the wear-resistant hardness of nickel. It is an ideal solution for processes that cannot use conventional lubricants.
• ASTM B733
• AMS 2405
A process called electrolysis is used to create a silver-plated bolt. Silver is often added to copper, steel, titanium, and aluminum bolts. Silver provides additional durability, lubricity, and wear resistance especially at elevated temperatures. Silver plated bolts are also highly resistant to chemical and acid corrosion. Since silver is a highly conductive metal, it is also used to increase electrical conductivity.
• ASTM B700
• AMS 2410, AMS 2411, AMS 2412
Zinc coatings create a physical barrier between the bolt and environments rich with air and moisture to help further prevent rust. Galvanizing is the process typically used to apply zinc coating; primarily hot-dipped galvanizing or electrical galvanizing. Mostly used on alloy steel bolts, zinc coating is an economic way to extend their life span – by giving them a sacrificial layer of first response to rust prevention. Even when scratched, zinc coated bolts will be less likely to rust as fast as those non-coated.
• Hot-dipped galvanizing ASTM A123, ASTM A153, ASTM A767
• Mechanical plating ASTM B695
• Electro-galvanizing ASTM A879
• Zinc plating ASTM B633