Are screws rust-proof?

Most outdoor screws have a polymer coating, which makes them rust-proof. Even then, if the application doesn't match the type of coating, your screws can and likely will rust.

When building something, reaching for the screws you already have is common. Being resourceful is good, but only when you're sure that the fasteners that you have are the ones that are right for your build. Not all screws are rust-proof, and even ones with corrosion resistance aren't rust-proof in all applications. So let's break down screws and their coatings based on their application. This will help identify what screw is rust-proof in your specific application, making your builds last longer!

Introduction to Screw Materials

Screws are definitely the unsung heroes of your builds. The level of attention to detail that goes into each one of them is immense. Something our Parts of a Screw post covers. Today, however, let's take a closer look at the materials that make up the screws we use.

The Base Materials of a Screw

Screws can be made from a variety of materials. Literally anything solid that can sustain some level of torque. Some of the common materials are:

1. Steel Screws: Steel Screws are the workhorses of the screw world. They are relatively cheap and are liberally used across projects. These boys will hold on to materials for dear life, but they will rust over time. This would happen rather quickly if placed in outdoor or moisture-prone areas.

2. Stainless Steel Screws: If you are seeing a screw used outdoors, then it's most likely is a stainless steel screw. These screws are rust-resistant. Stainless Steel Screws are pretty much the standard. They are often combined with different coating materials to give them greater corrosion resistance.

3. Brass Screws: Brass is resistant to rust but not as strong as stainless steel, so they are primarily used for decorative purposes. Brass will develop a patina over time, but that does not affect its structural integrity in any way.

4. Aluminum Screws: These are lightweight, rust-resistant screws. They are used in outdoor conditions but not for building or construction projects. We see aluminum screws being used in machinery like cars, lawnmowers, water pumps, etc.

In the following sections, we'll dive deeper into the characteristics of these materials and their rust resistance.

Types of Screws and Their Rust Resistance

They say the success is the sum of details, which is certainly the case regarding screws. Let's see what detail makes your screws rust-resistant.

Stainless Steel Screws: The Rust-Resistant Choice

Stainless steel screws are the almost rust-proof rockstar. Stainless steel is an alloy with multiple metals that give it its rust-resistant property. Chromium is the key differentiator here. When the alloy is formed, the chromium forms a thin but protective layer on the surface of the screw, shielding it from corrosion. This is what makes them stainless. This makes stainless steel fasteners popular for outdoor and marine applications. Yes, stainless screws are good enough to spend most of their lifetime submerged!

Steel Screws: The Workhorses

We already covered steel screws in the post before, and they are great. They are the workhorse of the screw world; what they lack in rust resistance, they more than make-up for in strength. They are cheap and easy to manufacture, so they are cost-effective and the only choice for most indoor projects.

Galvanized Screws: A Corrosion Barrier

Galvanized screws are a little different, they are often called zinc screws, but they shouldn't be confused with pure zinc screws. galvanized screws use an iron and/or zinc coating as a sacrificial layer. This layer corrodes in place of steel, thus prolonging the life of the screw. There are 2 types of galvanized screws. One is the hot-dipped galvanized screws, which are dipped in hot metals to form a layer of iron and zinc. The other type is mechanically galvanized screws; these are just zinc-coated screws.

Now you would ask what kind of application these are good for. And if stainless steel screws are so rust-resistant, why would someone use galvanized screws. The answer is simple: these screws are great for use indoors in moist or humid regions where rust is not a major concern. By no means are these to be used in areas of high water exposure. They also come in at almost half the price of stainless steel screws. This doesn't seem like much when it's a couple of screws, but these costs can make a huge difference on large projects.

Brass Screws: Shiny and Corrosion-Resistant

Brass screws are largely used for aesthetic purposes. With dark wood finishes, these screw head doesn't stand out and blends well, making them popular for indoor applications where screws will be visible. The copper content in brass screws also gives them natural protection against rust. These screws will develop a natural patina over time, which won't affect its strength but will affect how they look.

Aluminum Screws: Lightweight and Rust-Resistant

Aluminum is naturally corrosion-resistant, and it's super lightweight. They are often used in coastal regions where sea salt can wreak havoc on other metals. The natural oxide layer on aluminum acts as a shield against rust, making them a great choice for rust-free installations.

Aluminum screws are liberally used in automotive, marine, and aerospace applications. They are relatively expensive, which makes them undesirable for most home projects. HVAC and Air Conditioning systems almost exclusively use aluminum screws within the home, which makes sense because those systems are constantly exposed to moisture.

Tips on Choosing Screws

To help you navigate the wide spectrum of materials, we have compiled a set of tips that help ensure that your projects go as planned. If you still have doubts, why not reach out to us, and we will help you figure things out.

1. Consider Your Material
   Different materials require different types of screws. For wood, opt for wood screws; for metal, go for self-tapping or sheet metal screws. Some screws are specific to your projects; these include drywall screws, particle board screws, and concrete screws.

2. Mind the Length
   Screws should go through your material of choice without sticking out or destroying the material they are screwing into. Measure the thickness of your material and then determine the right length of screws for the task. If you're still in doubt, check out our post What size screws do I need?

3. Assess the Load
   Heavier loads require heavy-duty screws made with strong materials. These screws also feature specific thread types, which boost their performance. Heavier loads will likely use steel screws; in outdoor environments, stainless steel screws are the way to go.

4. Environmental Conditions
   Use rust-proof screws like stainless steel screws in areas with high moisture levels. Indoors, where the moisture levels are low, you can get away with ceramic-coated zinc screws. In most wood-based applications that don't encounter a lot of moisture, steel screws are good enough.

5. Screw Head Type
   Screw heads don't have anything to do with the strength of the screw but can affect your build's overall resilience. Screws with a bugle head sit flush with the surface, making them more aesthetically appealing, while the ones with a round head protrude from the surface but offer better hold.

6. Drive Type
   The drive type that you choose will depend on the material that the screw is going into. Material that requires a high level fo torque will use a square or a TORX drive. Commonly, you will find that Phillips head and flathead are just good enough for most applications.

7. Thread Type
   Threads can be fine or coarse. Fine threads offer better holding power, while coarse threads enable quick assembly. These, too, will be influenced by the type of material. Generally, metal uses fine-thread screws, and wood or concrete uses coarse-thread screws.

8. Quantity Matters
   Getting the right amount of screws is also key to the success of a project. We have a nifty way of calculating this for your drywall and deck construction projects.

9. Quality over Cost
   For long-lasting projects, always invest in quality screws over the cost. Name-brand screws like Screw Stop are always better than the sketchy-looking ones you'd find in your hardware store.

10. Tighten Properly
    Use the right amount of toque for each job that you are working on. Overtightening is never a good practice.

These tips are a great way to ensure that your project goes according to plan and lasts longer. Yes, material of the screw and its environment matter, but so do the factors mentioned above. To set you up for success, we have compiled posts that will guide you through some of the specifics you should consider. They also help if you just want to geek out a bit!

What are the 5 parts of a screw?

What are the 6 basic types of screws?

What are the longest-lasting screws?

What are the best quality screws?

Conclusion

In conclusion, not all screws are rust-proof. Most screws are, but the level of corrosion resistance for them will vary based on the kind of application that you need them for. Stainless steel screws are the ones that offer the best compromise of rust resistance and price. Galvanized screws are suitable for moist areas but not for applications with high water exposure. Aluminum screws the screws with maximum corrosion resistance but are expensive, making them ideal for automobiles and HVACs only. For most projects, stainless steel screws is the way to go!