How much flood water does it take to damage a car? Does it matter if it’s salted or fresh?

JACLYN DIAZSeptember 4, 2023

Between hurricanes, record rains and big tides; The Americans drove through a lot of floods and puddles.

All the water will damage your car.

You may not know it, but even rainwater is caustic.

Here’s the difference between salt water flooding and rainwater flooding and damage to your car.

“Any water can be caustic because rainwater contains acid. You’ve heard of acid rain,” said Mike Porcelli, master mechanic, automotive engineering professor and consultant. “So that can cause a lot of corrosion. And salt water is exponentially worse than fresh water. “

Porcelli refers to himself as MD, Machine Doctor.

Salt attacks metal

“Salt is very corrosive. It attacks metal, especially metals like aluminum and magnesium. When aluminum wheels sit in salt water or even park cars near the ocean, the salt eats away,” he said. “I saw a car the other day, we opened the hood, the aluminum strut (under the hood) was completely corroded. And I said, ‘This car has to be near the ocean.’”

Cars lie in flood waters from Hurricane Idalia after it passed off the coast of Tarpon Springs, Florida.

Even the ocean’s salt mist disperses salt in the air that can travel.

Porcelli said the literature claims it can travel 60 miles in high winds.

He said that the side of a parked car that faces the sea breeze wears out faster than the other side.

Cars lie stranded in flood water on Sheldon Road south of Ford Road in Canton, Michigan.

“If you have an electric car or an internal combustion engine or a hybrid; Salt water harms all vehicles,” Lauren Fix, The Car Coach, told FOX Weather. “And what it does is it rots things that you don’t think about, like the exhaust system, the brake lines and the fuel lines.”

She held up two brake lines. One was silver and clean. The other was on a car in Naples, Florida that recently felt the effects of Hurricane Idalia and was devastated by Hurricane Ian.

She said rust and corrosion occur within a very short period of time.

A car is pictured on a flooded street after torrential rain from Tropical Storm Hilary in Cathedral City, California.

Failure of these lines can result in the brakes not working.

Combustible fuel may leak instead of getting from the gas tank to the engine.

Flooding can be disastrous for electric vehicles

“Also, salt water is very, very corrosive on electric vehicles. If you have an electric vehicle that has been subject to a flood. Don’t drive with it. Don’t even try to start it,” Fix said. “Contact your insurance agent and have him pick it up. Take it to your local store and see what they can do.”

Several electric vehicles caught fire after flood waters from Hurricane Idalia receded.

A car is submerged in flooded water as Tropical Storm Hilary hits Cathedral City, California.

Acid dissolved in rainwater damages the paintwork

Salty air and fresh rainwater also eat away at the paintwork. He said salt water is acidic too.

“It eats into the paintwork. After a rain shower, you can see the water beading on the car and leaving a small ring after it dries, Porcelli said. “And the acid eats away at the paint. And the only way to remove that is to remove some of the paint by cutting it off below the craters made by the acid.”

Corrosion is only part of the problem when water gets into your car. Standing water leads to the formation of mold and mildew.

A car is parked in flood water as Hurricane Idalia makes landfall in the Big Bend region of Florida's Gulf Coast. — A car is parked in flood water as Hurricane Idalia makes landfall in the Big Bend region of Florida’s Gulf Coast.

“If it (water) gets inside (the car), professional help is needed,” advises Porcelli. “Even if it’s just taking the carpets out, drying them, sanitizing them, and putting it all back together.”

He said that steam cleaning, drying and disinfecting a car would cost about $1,000 if caught quickly.

After mold and mildew develop, you may need to replace carpets and rugs. Also, foam in the seats becomes moldy and rots.

Electronics and water don’t mix

But the biggest problem with modern cars and flooding is the electronics, he said.

Cars got stuck in the mud on a street in Cathedral City, California. — Cars got stuck in muddy flood water on a street in Cathedral City, California.

“Everything is controlled by computers. The power windows are controlled by a computer. The lights are controlled by computers. So every electronic system from the engine to the transmission, taillights and even the radio is controlled by computers,” said Porcelli. “Some of these computers are under the seats or deep under the dashboard. If water enters the car and floods the floor of the car, there is a risk of these computers getting soaked.”

He said this is why most insurance companies surrender flooded cars even when there is no visible damage.

Driving on salty roads in snow and ice is just as harmful.

The snow gets into the nooks and crannies under a car. Even after the snow has melted, salt residues remain.

fight back

Porcelli has several tips to keep your car in good shape:

Wash your car, the sooner the better, to minimize corrosion. Some car washes have an optional underbody spray.
Have your car professionally cleaned and waxed once a year. Keep it clean and reapply the wax every month or two.
Do not drive through deep water.
Repair dents, scratches and chips before corrosion sets in.
Be careful when buying a used car after a storm. Porcelli inspects used cars for customers before they buy a car for between $100 and $300. He said ask for an experienced mechanic who can spot flood damage. Car Fax only captures about 85% of reported problems, he said.