If you’re planning on building or repairing a deck, then you need to use the right fasteners. Decks are subject to year-round moisture from humidity, rain, dew, and snow, which means the screws you use for your deck must be protected against rust and corrosion.
If you head down to your local hardware store, you’re bound to find a huge selection of deck screws with varying levels of weather protection. So, will these deck screws rust?
Deck screws can rust, just like any other type of fastener. It really all depends on the material used and what type of protective coating or plating is used. Stainless steel screws tend to offer the highest level of rust protection, while galvanized steel and polymer/epoxy coated steel offer varying degrees of rust protection depending on the specific materials used.
Let’s take a closer look at what causes deck screws to rust, how you can prevent this from happening, and how to choose the right deck screws for your needs.
What Causes Deck Screws to Rust?
Deck screws, just like wood screws and other metal fasteners, will rust when the metal inside them is exposed to moisture and air.
Stated in more technical terms, rust is the result of steel corroding after the iron particles have been exposed to oxygen and moisture. When steel is exposed to water, the iron particles inside it become oxidized and form Fe++ which then reacts with electrons to form hydrous iron oxide (FeOH), better known as rust.
However, you don’t need to be a chemical engineer to understand that the level of corrosion resistance you’ll need for your deck will depend on how much moisture they’ll be exposed to.
Which Deck Screws Should I Use?
When selecting deck screws, there are two main questions you should ask yourself.
Firstly, what level of moisture and harsh weather will they be exposed to? And secondly, how long do I expect these fasteners to last?
Moisture has a way of working its way through screws protective coatings and plating over time, which is why you want to select fasters that are appropriate for your climate.
While moisture is the primary element that causes corrosion and rust, saltwater can greatly accelerate the process. If you’re building a deck in a coastal region, you’ll need a much higher degree of corrosion resistance than if you were building it in a dry, desert region.
When building or repairing a deck, you’ll also want to consider how long you want it to last. Not every deck has to be built to last a lifetime, and sometimes your priority is cost-savings over durability.In that case, going with cheaper galvanized screws makes sense over choosing pricy stainless steel screws.
Types of Deck Screws
There are three primary types of deck screws: galvanized steel, coated steel, and stainless steel. Each screw type has its own set of strengths and weaknesses, so you’ll want to weigh these factors against each other when making a decision.
Galvanized screws are the cheapest option, and offer the lowest level of corrosion resistance. These screws typically feature a zinc coating that offers some protection against moisture, but not as much as the other screw types.
You can expect galvanized steel screws to last about 10 to 15 years in moderate conditions, so they’re not “lifetime” fasteners.
Within galvanized deck screws, there are two primary types: mechanically galvanized and hot-dipped.
Hot dipped deck screws are immersed in molten zinc, producing a thick, durable coating that can sometimes be a little lumpy. Mechanically coated screws are designed to overcome this, resulting in a thin smooth coating free of clumps.
Hot dipped galvanized screws offer a higher level of corrosion resistance than mechanically coated, as the corrosion protection is directly proportional to the zinc coating thickness.
Another thing to mention is that of the two types only hot-dipped galvanized screws are rated for use in pressure-treated lumber. Pressure-treated lumber is increasingly popular for all types of deck building and features a copper additive that will rapidly corrode fasteners that don’t have sufficient protective coating.
Next up in terms of corrosion resistance is polymer or ceramic coated steel. These deck screws are becoming increasingly popular, and offer a nice mixture of corrosion resistance and price.
There is a wide range of different coating types and designs here, but the basic idea is a non-reactive coating is applied over zinc-coated steel. This results in a long-lasting corrosion-resistant finish that manufacturers claim lasts as long as stainless steel.
The polymer coating is generally superior to older-style ceramic coating in terms of durability, as is less prone to chipping off during installation. These screws can also be used in pressure-treated wood without worrying about them corroding from the copper additives.
If you’re looking for a highly-rated polymer-coated deck screw check out these Power Pro Premium Wood Screws.
Stainless steel deck screws are the crème-de-la-crème of deck screws and will last for as long as the deck does. They aren’t exactly cheap though, so they’re not the ideal choice if you’re looking to lower construction costs.
Stainless steel is naturally corrosion-resistant. Rather than using some form of coating to protect the cheaper alloy steel, the entire fastener is made from a corrosion-resistant material.
There are several grades of stainless used in deck screws with the most common ones being type 302/303/304/305. The differences between these are fairly minor and have to do with the specific alloys used.
There are also type 316 stainless steel deck screws, which feature a large amount of molybdenum to further increase corrosion resistance. This type of steel is often used in marine environments – so it’s more than tough enough to handle coastal deck construction.
|Screw Type||Cost||Corrosion-Resistance||Ok for Pressure Treated|
|Galvanized (Mechanical)||Low||Low||Not Recommended|
|Galvanized (Hot Tipped)||Low||Medium||Yes|
|Stainless Steel||High||Very High||Yes|
How to Prevent Deck Screws from Rusting?
The best way to prevent deck screws from rusting is by using the right ones for the job. Any coating of grease or rust inhibitor will wear away over time.
That being said, if you want to increase the corrosion resistance of your fasteners temporarily, applying a coating of paint, oil, or petroleum jelly can help somewhat.
Another thing to consider when selecting a deck fastener is whether or not you’ll be using pressure-treated lumber. If you use a fastener that’s not rated for use in this type of wood, it will rapidly corrode, leaving you with an annoying repair job.
To wrap things up, the answer to the question “Will deck screws rust?” is yes.
All deck screws aren’t made the same. While stainless steel deck screws are virtually corrosion-proof, cheaper galvanized steel screws will eventually corrode given enough time in an outdoor environment.
That means you’ll want to carefully weigh your preferences when selecting a deck fastener. Screws with the highest degree of corrosion-resistance cost significantly more than those with less.
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