How to Protect Your Car From Road Salt in the Maritimes

How road salt actually rusts a car

Rust needs bare steel, water and oxygen. Salt doesn't add much of its own; it speeds the whole reaction up and keeps the metal wet. New Brunswick spreads about 150,000 tonnes of salt a year on provincial roads, according to the province, and that salt does exactly what it's designed to do: it turns snow and ice into brine. That brine gets thrown up into wheel wells, frame rails, rocker panels, seams and every bolt head under the car.

Here's the part most people miss. The province notes that salt stops being practical below about -10 °C, so most of it goes down on those slushy days around the freezing mark. Those are also the days when the underside of your car stays wet and the chemistry runs fastest. A deep freeze at -25 °C is actually easy on the metal. A week of grey slush on Main Street in Moncton is not.

Maritime driving adds its own twist. We get freeze-thaw cycles all winter, so brine gets into a seam, freezes, opens it up a little, thaws and soaks in deeper. If you live near the water in Shediac or Cap-Pelé, there's salt in the air on top of what's on the road. And a heated garage, as nice as it is, melts the packed slush in the wheel wells and keeps everything warm and wet overnight. That doesn't mean park outside. It means rinse.

How often should you wash salt off your car?

Every week or two while there's salt on the roads, and after any big storm once the roads have been treated. The goal isn't a shiny car. It's getting the brine off the underside before it sits there for a month. After a four-year look at salt-related brake line failures, the U.S. highway safety agency (NHTSA) told owners in salt-belt regions to wash the undercarriage regularly through the winter and give it a thorough wash in spring.

Pick a mild day, ideally above zero, so the doors and locks don't freeze shut afterward. An automatic wash with an underbody spray is the easy option. At a wand bay you can do better, because you can aim. Spend your time underneath, not on the paint.

• Inside the wheel wells and behind the plastic liners
• Along the frame rails and the pinch welds under the doors
• Behind both bumpers, where slush packs in
• Around the brakes and suspension at each corner
• Open the doors and rinse the bottom edges and drain holes
• Dry the door seals after, or they'll freeze to the body

Oil spray or undercoating: is rustproofing worth it?

It depends on how long you'll keep the car. We don't apply rustproofing at OnCall, so we've no stake in which kind you pick. Here's how the options compare in plain terms.

Drip oil spray is a thin oil that creeps into seams and inside panels. It's usually redone every year, and it drips on your driveway for a day or two afterward. Some shops drill small holes to reach inside doors and rockers, then plug them. In our view it's the most forgiving option on an older car that already has some surface rust, because it keeps moisture off without sealing anything in.

Dripless or wax-type sprays are thicker and much less messy. The trade-off is that a thicker product doesn't creep as far into tight seams. Rubberized or tar-style undercoating forms a hard shell, which quiets road noise, but once it cracks it can hold salty water against the metal where you can't see it. Never let anyone put a hard coating over existing rust.

On the other side, Consumer Reports says modern cars come with factory corrosion protection and advises buyers to skip the dealer-added undercoating. That's a fair point for a lease or a car you'll trade in three years. If you plan to drive the same truck around New Brunswick for 12 winters, a yearly oil spray is a reasonable bet. Either way, read your corrosion warranty before anyone drills holes, and remember that no spray replaces washing.

Road salt and your brakes: the Maritime problem nobody talks about

Salt rusts brakes long before you see rust on the body. On a Maritime car, a lot of brake trouble isn't pads worn out from hard driving. It's hardware that's seized.

The caliper slides on two greased pins. Salt gets past torn rubber boots, the grease dries out and the pins rust in place. Now the caliper can't float, so one pad does all the work. The classic sign is an inner pad worn down to metal while the outer pad, the one you can see through the spokes, still looks half new. Other signs are a pull to one side, a wheel that's much hotter than the others after a drive, a burning smell, or a grinding noise that shows up out of nowhere.

Rust also builds up under the ends of the pads where they sit in the bracket. It swells and pinches the pads so they drag or stick. Rear calipers and parking brakes get it worst, because rear brakes do less work and don't clean themselves off. And rotors rot from the inside vanes and the edges, not just the face you can see.

Then there are brake lines. Steel lines run the length of the car, clipped to the body and right in the spray from the wheels. NHTSA tells owners of older vehicles in salt regions to watch the brake fluid level, notice any change in how the pedal feels and look for fluid leaking under the car. If a line has flaking, scaly rust, the advice is to replace the whole line, not patch a section. A brake line that lets go doesn't give much warning.

What to check every spring after the salt season

Do it once the street sweepers have been through and the salt's off the roads, usually around the time you take the winter tires off. Start with a proper underbody wash. Then have the brakes looked at with the wheels off, because you can't judge inner pads or slide pins through a wheel.

A good spring brake service on a Maritime car means more than checking pad thickness. The pins come out, get cleaned and re-greased, boots get replaced if they're torn, the rust gets cleaned out of the pad brackets and the hardware gets replaced if it's tired. Done every spring, it can save a set of pads and rotors that would otherwise be scrap by next fall.

If you're getting your tires swapped at a shop, ask them to look at the inner pads while the wheels are already off. If you're in Moncton, Dieppe, Riverview or Shediac, we can inspect and service the brakes in your driveway. If a seized caliper bolt or a rotten brake line turns out to need a hoist, we take the car into a shop and manage the repair from there.

• Underbody wash once the roads are clean
• Inner and outer pad thickness on all four wheels
• Slide pins free and greased, boots intact
• Rust cleaned out of pad brackets
• Brake lines and hoses checked end to end
• Parking brake holds and releases fully
• Exhaust hangers and heat shields not rusted through