Why you should rustproof your car this winter

As winter approaches, and with it, rain and snow, many drivers know to start pulling out their ice scrapers and winter tires.

Rustproofing refers to the process of applying a treatment to your vehicle to prevent rust from developing. Depending on several factors – the type of treatment you use, how often you drive your car, and the weather conditions it’s exposed to – this treatment could last about a year or the entire lifespan of your car.

But not every car needs to be rustproofed. Here, we break down everything you need to know about rustproofing your car, from how it works, how much it costs, and when it’s worth the investment.

Why does rust even happen?

Rust develops when iron, oxygen, and water interact. The chemical reaction between these elements is a type of corrosion that eats away at the surface on which it forms, weakening the durability of the material.

Over time and left untreated, this corrosion can potentially cause structural damage and, depending on where it forms, make your car unsafe to drive.

Cars that are regularly exposed to rain and snow are more at risk of developing rust, but salt can also contribute to the problem. If you’ve ever spent a winter trudging through heavily salted roads on foot, you might be familiar with the havoc salt can wreak on your footwear. Salt has a similar effect on cars, corroding the paint and exterior of vehicles and making them more susceptible to rust.

As of 2018, Statistics Canada reported that about five million tonnes of road salts are used in Canada each year to mitigate dangerous conditions on roads.

Related: What to know about winter driving and car insurance in Canada

What does rust look like?

Rust falls into one of three categories:

Surface rust: The earliest, and least severe type of rust looks like small, reddish-brown spots. This type of rust can form from minor scratches or chipped paint, and only impacts the top layer of the metal surface

Scale rust: If surface rust is left untreated, it can develop into scale rust. This is the stage when rust penetrates deeper into the metal and begins to flake

Penetrating rust: The most severe form of rust. This is the stage where the corrosion has eaten through the metal, compromising the integrity and safety of your car

Surface rust is relatively easy and affordable to repair by sanding off the rust, painting the area, and sealing it off from the elements with a clear-coat finish. But once it starts to flake, the damage could become dangerous – especially if the rust has developed in structural elements of your car like the frame, the underbody, or the exhaust system, including its precious catalytic converter. Treating more severe types of rust should be left to professionals.

Related: The most stolen parts of a car

What does rustproofing involve?

Regularly washing your car can keep your car free of salt and other substances that could potentially cause rust. When you rustproof your car, however, you create a physical barrier between these substances and the surface of your car. The most commonly available options are:

Drip oil spray

The most common and frequently recommended method for rustproofing involves a lightweight oil that you spray on your car. With this method, holes are strategically drilled in your car so the oil effectively can reach the nooks and crannies of your car frame.

The downside to this option is that the oil can take about two days to fully dry. Reapplying the treatment each year is recommended.

Dripless oil spray

Less viscous than drip oil spray, dripless oil hardens much faster than its more lightweight counterpart to form a firm, wax-like barrier over your car. As with drip oil spray, holes are drilled into your car to maximize coverage.

Because it is thicker, dripless oil will cover less surface area than drip oil spray. It is also prone to cracks, which can trap moisture and result in corrosion. It is recommended to reapply dripless oil spray annually.

Tar spray

This procedure involves applying a tar-like substance to the exposed parts of the undercarriage of your car. The substance theoretically hardens into a permanent shield against salt, moisture, and other elements, but in practice, the rigidity of the barrier makes it susceptible to cracking – and trapped moisture. Because of its thickness, it also has a hard time reaching nooks and crannies.

While annual reapplications are not necessary, annual checkups are recommended. This type of rustproofing is also known as undercoating.

Electronic module

The newest option on the list involves installing a small device in your car, which emits a constant, weak electric current through the metal of the vehicle to prevent it from rusting.

While this is the least invasive option out there for rustproofing, experts and consumers alike are divided on its efficacy.

Related: What is a preferred body shop for auto insurance?

What are the benefits of rustproofing your car?

Rustproofing may not be necessary for everyone, particularly if you don’t plan on keeping your car for a long time, or if you have a specific model of car that is not recommended for rustproofing, such as certain electric vehicles.

For those who choose to invest in the process, though, there are a bunch of benefits. These include:

Extending the lifespan of your car

By taking steps to ensure your car avoids rust damage, you could increase the lifespan of your car.

Higher resale value

A rust-free car will likely command a higher trade-in value than one that’s seen rust-related damage.

Lower repair costs

Protecting your car from rust means keeping it safe from cosmetic and structural issues that arise because of rust.

How much does it cost?

The cost of having your car professionally rustproofed will depend on the size of your vehicle (i.e., the bigger your car, the more you can expect to pay). The cost of spray applications typically starts at less than $200, while electronic modules can cost anywhere between the low hundreds and more than $1000.

Should you rustproof your car?

Many modern vehicles are manufactured with rust protection nowadays, making it unnecessary to seek out additional rustproofing when you first buy your car.

With a used car, however, rustproofing could be advisable depending on whether it was initially manufactured with rust protection, the level of wear and tear on any existing rustproofing treatment, and how long you plan to hold onto the car.

If you plan to keep the car for more than a couple of years and it hasn’t ever been rustproofed – or hasn’t been rustproofed in a while – it’s worth looking into a treatment.