While they don’t make much of an impression, galvanized screws are a big part of what keeps the world fastened together. In fact, we owe so much to these tiny titans, that without them we’d be undoubtedly living in thatched huts. These little giants of the construction world help to keep structures intact and strong due to their ability to resist corrosion. In order to prevent metal from corrosion, a process called galvanizing is used for screws. Here, the bare metal is treated to a thin coat of zinc. This application of zinc works as a barrier that protects the metal screw from oxidation.
What is Oxidation?
When you take a bite out of an apple, and leave it in the open air, you’ll notice it soon turns brown. Similarly, when an object made of metal such as an old car or bike sits in the elements, brown rust appears. What is happening is a process called oxidation. In oxidation, the object in question loses electrons. Steel is one such metal which loses electrons easily. So, to prevent this, tools and other items made from metal such as screws, are galvanized to ensure longevity and strength retention. For instance, when metal is galvanized it’s protected from the elements. This means that any galvanized metal used outdoors would be protected from any oxidation. Simply put: No rust.
Methods of Galvanizing Metal
The coating of zinc ensures that the metal is protected from moisture, rain, snow, ice or chemicals. So, a galvanized screw will be able to tolerate alterations in climate, season, temperature, salinity and humidity. This barrier isn’t indestructible, however. If the layer of zinc suffers enough damage to allow moisture to get through, then the metal beneath will corrode. As such, it’s crucial to only purchase galvanized screws from a reputable company. When you visit a hardware site, you’ll come in contact with both hot-dipped and zinc plated galvanized screws.
Hot Dipped Galvanizing
To get an idea of the type of hot dipped galvanized screw, take a look at any hardware site). When you read the descriptions, notice that screws such as this Hillman screw are described as being “hot dipped”. Here, the screw is being dipped into molten zinc. Once finished, the screw has a protective shield which creates a corrosion resistant screw, perfect for outdoor use on decking, patios, playground equipment, fencing and so on.
The zinc plating method of galvanizing gives the screw a zinc layer. Whereas the hot dipped screws are for both interior and exterior use, the zinc plated screw is often chosen for interior projects. Zinc plated screws are not as tough as hot dipped screws. An example of a zinc plated screw is the Everbilt wood screw. Zinc plated, galvanized screws are used as interior fasteners such as door hinges and other finishing tasks.
In this process, the screws are placed in a type of rotary barrel. They are then tumbled with a mix of zinc powder and glass beads. How much corrosion protection you get is directly related to the amount of zinc powder used. Mechanically plated screws are not as strong as hot-dipped, so know the project you’re working on and ask your hardware dealer if not sure.
Galvanized Screws and How They’re Used
- Roofing Screws – There’s no better place to start when dealing with galvanized screws than those used in roofing. Here, the screws are in constant contact with the environment, so need to be strong. Not only that, but it’s important to consider the cosmetic implications of galvanized screws used in roofing projects. Unprotected screws will not only weaken over time, but risk leaving unsightly brownish-red discolorations on the home, due to oxidation.
- Outdoor Deck Construction – Decking gets hit by all the elements to be sure, so galvanized screws are a must for longevity and appearance. However, there’s another terror to confront which makes galvanized screws necessary: The pool. Not only are decks built for sunning and barbecuing, but also for pools. Pool decks come in many different designs, and are usually built around an above ground pool. Here, you’re not only dealing with weather, but also pool chemicals as the water splashes on the wood. By using corrosion resistant connector screws, the longevity and beauty of your deck will be secured. Simpson Strong Tie is a good example of a galvanized connector screw with its Strong-Drive SD connector screw. Another consideration you need to be aware of are the chemicals used in treated lumber. These chemicals can also attack plain steel screws, so use galvanized screws when working with treated lumber indoors or out.
- Lag Screws – One of the toughest screws available is the lag screw. (https://home.howstuffworks.com/lag-screws.htm) If you perchance to see a wooden swing set loaded with happy kids, then know that it’s strength is partly due to lag screws. Lag screws are also used on retaining walls, pool and patio decking. Also known as lag bolts, these galvanized screws are employed when wooden structures are used to bear heavy loads, or for security reasons. Benefits of lag screws include ability to bear intense weight, made for interior and exterior use, and endure these weights for extended periods of time.
- Composite Deck Screws – Galvanized composite deck screws have both exterior and exterior applications. These screws are meant to be used for composite materials, plastic and wood. They are designed to lessen or eliminate any cosmetic issues that can occur with some composite materials. As an example, take a look at this composite screw by Camo. As you can see, the composite deck screw is a multi-purpose fastener for a variety of materials. Many of these screws also come in a variety of colors, depending on their manufacturer. Thus, leaving a clean finish along with a color similar to the decking material used.
When working on do-it-yourself projects such as swing sets, outdoor sheds, and the like, it’s critical that you’re aware of the importance of using galvanized screws. While it’s tempting to go on the cheap, the costs of galvanized screws is so minimal that it only makes sense in the long run to purchase from the best supplier possible. As you’ve seen, we’ve included links from well-respected suppliers such as Camo, Hillman and Everbilt to help get you started. By visiting a reputable hardware supplier, asking questions before you purchase, you’ll obtain the perfect galvanized screw for your project, whether it’s working with a composite PVC material, treated lumber or metal.