When you install a fastener, you want and expect that fastener to stand the test of time. For projects large and small, fasteners serve as the glue that holds together various pieces to create a structure or object that has integrity. But there's one enemy that can threaten that integrity and the strength of metal fasteners: corrosion.
More specifically, electrochemical corrosion — better known as “rust” — can reduce a fastener’s strength and render it useless. Thankfully, for construction professionals and others who use metal fasteners for projects, choosing the right materials and taking the right action can help reduce the possibility of corrosion and increase the chances that a structure remains strong over the long-term.
If corrosion occurs, it demands action. You can’t just wish it away and hope for the best. That’s why you must either do something to prevent corrosion or do something to fix the problem should it occur. Here’s a look at why corrosion occurs and how to prevent corrosion on fasteners of all kinds.
Why Corrosion Occurs
In simplest terms, corrosion happens when metal’s inherent properties begin to degrade. All metal, including the metal used in fasteners, holds electric potential. Metals have different types of electric potential, though. And when two metals interact with water, which is an electrolyte, a galvanic cell is created and an electric current begins to flow between the two metals. This low-energy galvanic flow begins to degrade one of the metals: the one with the higher electric potential, to be specific.
The higher-potential metals are known as “anodes,” and the anode metal’s atoms actually lose electrons to the lower-potential metal, known as the “cathode” metal. This transfer of electrons creates what we think of as rust in the higher-potential metal.
The farther apart two metals are on the electric potential spectrum, the more easily the higher-potential metal will corrode. For example, zinc, galvanized steel and magnesium are high on the potential spectrum, while silver, gold, zirconium, platinum and titanium are low on the potential spectrum.
It’s easy to see how fasteners corrode. If a fastener is made of a high-potential metal and installed in a low-potential metal, the possibility of corrosion is high — unless measures are taken to prevent rust and other corrosion from appearing.
How to Prevent Corrosion
The good news is that we have the information and technology to prevent corrosion, or at least limit its effects. The first step you should take is to use insulation, coatings or paint to seal fasteners that are a different metal than the material they will be installed into. These dielectric coatings can help limit the occurrence of rust and other corrosion.
Also, be sure to install fasteners in a way that delivers constant pressure. When the load a fastener bears is constantly changing, the constant changes can help accelerate the appearance of corrosion.
Finally, be strategic about the materials you choose to use in manufacturing and construction. The flow of electricity and the rate of corrosion are greater when flowing from a smaller object to a larger area. For that reason, you wouldn’t want to use zinc screws to fasten together stainless materials. If you did, the large gap in electric potential would quickly degrade the zinc screws, which would then weaken whatever you had built or constructed.
Instead, choose to use fasteners that are similar in electric potential to the materials they are fastening together. This will reduce the flow of electricity, which will then reduce the rate of corrosion.
Different Types of Corrosion
Corrosion can occur in different places and can look different, depending on the circumstances. Here’s a look at different types of corrosion you should be watching for:
- Galvanic Corrosion: This is the type of corrosion described above. It occurs when two different types of metal are joined, and electricity flows from one to the other, leaving behind corrosion.
- Uniform Corrosion: This occurs across the entire surface area of a fastener when it’s not properly coated or plated.
- Crevice Corrosion: Crevice corrosion appears in small gaps and openings in your fasteners that are not ventilated as they should be.
- Pitting Corrosion: Pitting corrosion is when tiny holes appear in a fastener, so tiny that they are difficult to detect. Pitting corrosion is most likely to occur in noble materials like nickel and chromium, but can be prevented by keeping surfaces clean.
- Intergranular Corrosion: Ever wonder why welders quickly plunge parts into water to cool them down? This is done to prevent intergranular corrosion, which occurs in stainless steel when it reaches extremely high temperatures. This happens during welding and hot forming.
About FMW Fasteners
At FMW Fasteners, we deliver a huge selection of materials that includes a number of different materials and corrosion-resistant finishes. If you’re searching for a specific fastener in a specific size made of a specific metal, we deliver the options you need.
You’ll always enjoy low prices and inexpensive shipping at FMW Fasteners. Shipping is even free on orders of $25 or more. Order in the exact amount you need and return what you won’t use at any time — as long as the materials remain in like-new condition. Make sure you’re preventing corrosion when you choose the right fastening materials from FMW Fasteners.