What Road Salt Does To Your Car & What You Can Do About It
In early 2015, Ford recalled close to a million vehicles, the Fusion and the Lincoln MKZ among them, all for premature rusting. Most of the vehicles affected were in the northern part of the country with heavy exposure to snow. In the winter of 2015, Toyota recalled a similar number of Tacoma trucks for a similar problem. Roads and bridges all over the snow belt have been reported to have rusting and corrosion.
The one common thread in all three examples is this: magnesium chloride, a highly effective deicing agent sprayed on roads in many states. While common rock salt used to be the agent of choice before, it used easily wash off, requiring repeated sprays. The staying power of magnesium chloride over regular rock salt has made it far more desirable. While it’s very good as a way to keep roads ice-free, however, it is nothing short of catastrophic for vehicle underbodies.
What does magnesium chloride do to your car?
All salts corrode metal upon contact. When your tires churn up road salt mixed in with snow, a lot of it tends to end up sticking to the underbody. While common salt does stick and does corrode, it tends to stay in undissolved crystal form until environmental humidity reaches a very high 70%. This isn’t common in winter. Magnesium chloride, however, dissolves at 20% humidity, which is common in winter. This means that when magnesium chloride gets on your car’s underbody, it turns into liquid acid and coats every surface. It is much more corrosive than rock salt, as a result.
Frequent advice for the salt problem is simply to never drive behind a salting truck and to shell out the $10 or $20 that it takes to get your car into a good car wash a day after every heavy snowstorm.
What if you’ve seen that nothing really happens?
No one you know may have ever taken the car wash rule seriously. They make have always washed only at the end of winter, and it may have never seemed to make their car worse. Should you really worry about rust and pay for a solution?
The problem with looking at the personal experience of friends is that they probably haven’t had enough time to truly experience what magnesium chloride can do. Many states have only recently switched to the substance, after all. The other problem is that new cars tend to be able to resist corrosion for longer, simply because they are newer. If a friend who has experienced no problems drives a new vehicle, the rust probably simply hasn’t had time to show. For anyone who drives an older vehicle, however, rust over the years is likely to have already weakened the metal. Magnesium chloride can hasten the process.
The truth is that magnesium chloride turns into acid, and acid does corrode metal and plastic.
How dangerous is it?
Corrosion in car parts is dangerous. People do report failed brakes, tripped engine warning lights and broken leaf springs. The older the car, the more quickly these problems show up. It’s important to take steps.
What else can you do?
While carwashes are a reasonable solution, they aren’t as effective as they might seem. When roads are sprayed, crews mix salt in with water and spray it. Liquid brine can get into every crevice inn your car. Car washes aren’t able to get that deep inside. Their wash detergents aren’t able to neutralize salts, either. Few carwashes use the low pH detergents needed.
While some truck and bus manufacturers have switched to expensive stainless steel underbody components, these aren’t an option for regular car owners. Rust prevention coatings are the most reasonable choice to go with. A number of possibilities exist. Some companies offer a thick, tar-based coating. These products work best with new cars that don’t have any rust to begin. Others offer an effective ceramic application.
Oil treatments, both the dripless and dripped varieties, work very well. The thin oil gets into every nook and corner of your car’s underside and provides effective protection. This substance tends to work on older cars with some rust damage, too. The best part is, it tends to cost as little as $75 an application.
You should look for a warranty
While a number of competing underbody protection products are on offer, only a few vendors are confident enough of the effectiveness of their products to offer a multiple-year warranty. If you can find this kind of warranty on a rust prevention product, you should get it, even if you don’t plan on keeping a new car any longer than five years. While the rust that develops in that period probably won’t cause catastrophic failure, it will lower the value of your car when you sell.