Looking for the right fastener for the job? While it may seem like an easy task, there’s a lot to consider when choosing the right ones for the application. Fasteners can include anything from nails and screws to staples and bolts and create the joint that holds components of various machinery or assembly together.
For that reason, they must be selected with care. But fastener selection goes beyond the device itself and must take into account the fastener finish. Fasteners typically come into contact with other metals and environments that can lead to corrosion and oxidation, so it’s important to choose a finish that will extend the life and performance of that fastener and corresponding joint.
Things to consider when choosing the right fastener finish include:
- Safety of the joint itself
- Functionality of the fastener
- Corrosion protection and service life
- Resistance to damage from handling
- Cost of the overall assembly
What is Plating and Coating?
Plating and coating refer to the finish that is present on the surface of a fastener. Different finishes are required for different applications, materials and environmental conditions.
According to ProPlate, Plating is the surface covering applied to a material that inhibits corrosion, as well as provides other benefits such as improved hardness and durability, reduced friction, altered conductivity and desired aesthetics. Plating occurs when a thin layer of metal coat is applied to a fastener, either through electric currents or a chemical process. Coatings are produced when material is placed on the substrate and acts as a barrier that offers protection from oxidation, wear and corrosion.
The materials most commonly used in fasteners include stainless steel, aluminum and brass.
Stainless steel is ideal for many heavy-duty industrial applications and offers the highest levels of corrosion and oxidation resistance, but can lack the strength found in other materials and can be quite expensive, according to LINC Systems partner BeA Fasteners. Some fastener materials are plated or coated to enhance corrosion resistance qualities, provide increased levels of durability or increased levels of attractiveness. In addition, some users prefer galvanized steel fasteners as a more cost-effective option for many applications.
What is Galvanization?
Galvanizing is one of the most common ways to protect metals like steel from corrosion and occurs when a thin layer of zinc is applied to the surface of the metal. The zinc acts as what’s called a sacrificial anode because when it comes into contact with a corrosive environment, it will “sacrifice” itself — protecting the metal underneath from rust, oxidation or damage, according to BeA Fasteners.
There are several different processes for galvanizing metal and all can achieve similar results. The most important thing to consider with galvanization, however, is the thickness of the actual zinc layer. Too thick of a layer can actually create an unusable fastener, but too thin of a layer will lead to premature corrosion of the metal underneath.
Below are the differences in galvanization processes:
Electro Galvanization uses an electric current in an electrolyte solution to transfer zinc ions onto the base metal. Benefits of electro galvanization are uniform coatings and precise coating thickness.
Mechanical Galvanization is a process in which zinc coatings are applied at room temperature without electricity or heat by tumbling the parts in zinc powder. Mechanical galvanization offers ideal sacrificial protection, but it’s important to note that the finish is thicker than electroplating.
Hot-Dipped Galvanization is the dipping of the base metal into a molten pool of zinc. Hot-dipped galvanization provides maximum corrosion protection, is relatively inexpensive, and is quick and versatile for various shapes. The downsides can be inconsistent coating thickness.
Did you know? BeA Fasteners shares that the easiest way to know if your galvanized steel’s zinc layer is adequate is to perform a salt spray test. If you see white rust on and around the fastener, you still have some level of protection. When you begin to see red rust, your zinc layer has degraded and isn’t providing protection from corrosion or oxidation.Need help selecting the right fasteners for you? Speak to a LINC Systems Team Member today.
What are the Other Common Types of Fastener Finishes?
Here are several of the most common finishes that are available for your fastening needs:
Black oxide is a thin coating for ferrous materials, stainless steel, copper and copper-based alloys, zinc and powdered metals that provides minimal corrosion resistance. This finish is often combined with an oil dip and used when an attractive look is desired.
Black zinc plating is zinc plating followed by a black chromate conversion coating that provides mild corrosion resistance and is thicker than black oxide.
Zinc electroplating, also known as zinc chromate or dichromate, is often followed by a chromate layer and used for hardware fasteners. The zinc oxide acts as a sacrificial anode if the barrier is broken, protecting the metal underneath. Zinc is an ideal finish for protecting steel from corrosion and preventing rust at a price point that is affordable and accessible. Zinc should not be used in marine or salt environments.
Cadmium finish provides excellent rust-resisting qualities typically used in marine and aviation applications, but has high levels of toxicity.
Chromate finish is a secondary dipping process after plating to provide very good corrosion resistance to zinc and cadmium plated parts. This finish is ideal for all metals and provides good corrosion resistance with a hard and stable finish. However, this finish can be expensive and difficult to apply.
Chromium finish provides a hard, lustrous finish, as well as good corrosion resistance for all metals, but can be expensive.
Ceramic coatings provide high levels of oxidation resistance in marine environments and are designed to last a long time, but can be pricey.
Learn more about various fastener finishes in this article from Machine Design.
LINC Systems carries fasteners such as corrugated fasteners, furniture clips, hardware, hog rings, nails, rebar tie wire, scrails, screws and staples in a variety of materials and finishes. Give us a call at 800-513-9918 to speak with our customer service experts for guidance in selecting the right fasteners for your needs. Or browse our website.