Why does it happen? In older cars it can mean that scratches went untreated or that a below average paint sub was left in the weather with no protective coat of wax for too many years. BUT why do newer cars rust?
You may have noticed some rust on your car, which feels out of place because your car just isn’t that old. Well there are several reasons for this, but generally it’s the result of something that happened, or didn’t happen, during the production of the vehicle.
Most newer cars don’t get a rust problem, but it’s such a pain to deal with let’s look at it in this post.
It’s the places we don’t see which tend to be where problems flare up. One factor that causes the underside and the wheel wells to rust is that this area gets a lot of exposure. Rainwater falls on your car and runs off, but water in puddles on the road get picked up and thrown up into the car from underneath as long as the roads are wet.
However, all cars get exposed to rain so why do some rust? The second factor is a lack of under-sealing. Under-sealing is essentially a coat of paint, which doesn’t have to look good, it just covers the raw metal preventing rust.
You most often hear the term under-sealing from a car salesperson, but it’s a real thing. It might seem like they’re charging you for something and then waving a magic wand over the car, but mechanics do recommend an under-seal. Its factory standard for most cars made in the US, but imported cars are hit and miss. Japan in particular often skips the undercoat as they have milder winters and want the buyer to have the option of saving the money. Under-sealing is particularly vital to make sure that cars don’t rust underneath the trim and bumpers, and the wheel-arches. This tough pain cope with road chippings.
A third factor in auto rust is if salt is used as a deicer in winters, or if you drive on rough roads. Rough roads can expose areas of your suspension that aren’t really made to sit out in the open. Even if this is temporary it can introduce dirty water to these parts, which will act abrasively to create areas that eventually rust.
Vehicles which travel through salty water are more likely to rust because the salt will act on metals such as nickel and chromium. Cars with an underside of metals such as aluminium and magnesium are less likely to rust, which are generally modern cars. It’s the steel chassis which are the pain.
To help prevent this you should wash behind the tires using clean, soapy water. Applying a pipe cleaner to hard-to-reach areas is also a plus. If there is an excess of paint or putty substance on the underside use sandpaper or an abrasive wheel to remove it.
Although pressure washers use massive amounts of water, they can also damage the underside and should be done sparingly.
Even when you get your undercarriage sealed.
The coating may get chipped when a person jacks up your car who doesn’t know what they’re doing.
Some “underseals” are a type of thick wax, which will prevent rust by denying air and water to the metal parts. It generally prevents rust but could melt in hot weather or be washed away too much water on the underside of the vehicle.
When you discover rust.
It’s best to start by cleaning surfaces like the wheelarch with a wire brush to remove flaking rust. Then apply a rust converter with a paintbrush for the best results.
Bitumen is a traditional patch for a rusty area, but it’s really inferior for a couple reasons. It doesn’t last that long. It should be applied with gloves and masks. It’s awkward to remove the excess. When dry it turns into a brittle substance and is liable to break off.
Some old-school mechanics will apply grease or old engine oil to problem areas. The problem is that this drip on the road and cause a hassle for motorcyclists and other road users.
When you have a classic car you will just have to face it, you will have to deal with tricky things like rust. It’s just one of those annoying things in life.