Auto Parts - How Often Should You Undercoat or Rustproof Your Vehicle?

The best time to rustproof or undercoat your vehicle shouldn’t be left to guesswork. Depending on where you live, your driving habits, and the type of vehicle you drive, there’s a recommended timeline you should follow to ensure your vehicle is protected from top to bottom.

Keep reading to learn the best interval to follow, when the best timing is for each, and how you can effectively apply DIY rustproofing and undercoating.

What Is Rustproofing vs. Undercoating?

A common error is using these two terms interchangeably, but rustproofing and undercoating are two very different processes.

Rustproofing is a protective chemical coating that slows the development of rust. It’s applied externally on body panels, such as fenders, tailgate, and upper body, and internally, for example, on seams, weld points, door cavities, rockers, and hollow frame and body members.

Undercoating is a wax or rubber-based coating sprayed on the undercarriage of your vehicle to block road salt, moisture, and debris. Both rustproofing and undercoating are complementary to each other and can be done at the same time to protect the entire vehicle.

While all vehicles can benefit from rustproofing and undercoating, Canadian drivers are even more in need of routine rust protection. Dissolved road salt sticks to the underside of the car and speeds up the growth of rust. Freeze-thaw cycles during the winter and early spring can also trap moisture in seams and panel gaps, which can lead to sneaky rust patches that can be easily missed.

How Often Should You Rustproof Your Car?

Since rustproofing is a preventive service, there isn’t a specific or mandatory timeline to follow. But it can wear off over time, leaving your vehicle vulnerable to the elements.

A baseline application interval is at least once every two years, but if you live in a coastal area, a region with heavy road salt exposure, or you take frequent short trips, then it may be wise to reapply your rustproofing chemicals every year.

How Often Should You Undercoat Your Car?

Like rustproofing, undercoating isn’t required for the safe operation of your vehicle, so there’s no hard rule for how often it should be reapplied. But general guidelines recommend every one to three years.

Most new vehicles already have factory rust protection from the manufacturer, but undercoating is most valuable once that factory coating starts to wear off, or if you live in high-salt regions. It’s worth applying undercoating if you recently purchased a used vehicle, especially if you bought it from a private seller or don’t have the vehicle’s complete service history.

What’s the Best Time to Rustproof or Undercoat Your Car?

It’s best to rustproof and undercoat your vehicle in the spring or summer when it’s warm and dry. These conditions are needed for the coating to adhere and cure properly onto the body of your car. This also ensures your vehicle is fully protected before winter road salt season begins.

DIY Rustproofing: Step-by-Step

Before you start to apply rustproofing chemicals, make sure you have these necessary items:

• gloves
• protective eyewear
• respirator mask
• car wash soap
• sandpaper
• wire brush
• rust protector spray
• tape or plastic to mask off different vehicle components

Once you’ve collected the above supplies, follow these steps for a successful rustproofing process:

• Step 1: Ensure the engine, exhaust, and brakes have fully cooled.
• Step 2: Wash your car, focusing on wheel wells and hard-to-reach spots.
• Step 3: Remove any existing rust using sandpaper for light discolouration on external paint and the wire brush on any flaking or weakened metal. Rinse again if needed.
• Step 4: Thoroughly dry your vehicle. Rustproofing cannot adhere to residual salt or moisture.
• Step 5: Mask off exhaust, brakes, and belts with tape or plastic before applying the rust protector in a well-ventilated area and away from any open flames or sources of heat.

If you’re going to access the underside of your vehicle for undercoating, use a jack and jack stands on level ground, engage the parking brake, and chock the wheels that will be staying on the ground. Always follow the rust protector’s safety sheet and apply two coats for full coverage.

If you’re unable to safely reach certain areas of your vehicle for full rustproofing or undercoating, reach out to your local NAPA AUTOPRO service centre for professional help.

More Tips to Prevent Rust

Rust development is a natural process that can be hard to definitively prevent. Here are a few routine ways to effectively slow down rust at home:

• Wash your car every two weeks to remove grime, moisture, and salt.
• Wax your car at least twice a year.
• Repair stone chips on your vehicle’s body as soon as possible, using touch-up paint and a rust-inhibitor primer.
• Vacuum and dry your vehicle’s interior, especially after wet or snowy weather.
• Inspect your vehicle for rust at least twice a year.
• Lubricate your exterior hinges and locks each season.

Why This Routine Matters

Rust prevention is about so much more than your vehicle’s appearance. Untreated rust weakens structural integrity, reduces resale value, and can eventually affect safety-relevant components, such as your brake lines and frame rails.

Staying on top of rustproofing and undercoating helps your car last longer, can hold its value, and saves you from potentially large and costly repairs later.

Rust can be sneaky. If you’re not routinely checking, it may seem like a new rust spot has appeared overnight. Luckily, routine rustproofing and undercoating can help you slow rust development.

For all your rustproofing needs, visit your local NAPA Auto Parts store to speak with an automotive expert or browse our full range of rust protection supplies at www.NAPACanada.com.