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I have a 2009 Hyundai Tucson with less than 30,000 miles on it. My mechanic always compliments me about the great mechanical care I take to my car, following the owner’s manual to a T. I also get a professional detain done once a summer. The detailer complimented me on how clean my car was, saying it didn’t belong there! Ha-ha! I just like a clean car and take great care of my fabric and wash it once a week.

The detailer said my car will last me forever if I keep it up except for one thing: I’ve neglected to undercoat or rustproof underneath here in Northeast Ohio’s winters where your car gets asSALTed like crazy. Too late now?

I’m thinking that doing it now will just cause any debris underneath to become trapped, causing it to rust quicker. Or will someone who specializes in undercoating or rust proofing have the tools to clean underneath before applying any undercoating?

Undercoating no. Rustproofing can help.

Undercoating is a sound deadening material that’s applied to the underside of the vehicle. And if not applied correctly can promote rust.

Rust proofing is applied to the interior surfaces of the body panels. This usually requires drilling holes in various locations so a wand can be inserted to apply the material to inside surfaces.

But your vehicle requires neither. Now that vehicles are made of aluminized steel rust proofing is no longer required.

When was the last time you saw a Rusty Jones or a Ziebart franchise?


Just ask your mechanic to look for rust each time it’s up on a lift.

Cheap idea!

Don’t apply any undercoating material that holds moisture in. It’s simple just to, once a year, crawl underneath the car with a foam brush and paint red grease on suspected rust areas. But, the rust will really occur between body panels in the rockers, fender seams and rear quarters. This is where the real rust will occur and there is nothing you can do except spray an oil based product or motor oil into those areas once every year or two. If you don’t, it will rust, guaranteed when exposed to salt and there is nothing else you can do. All cars are destined to rust in wet and or salt areas and this is the only ongoing treatment that works long term. Undercoating or rust proofing as a one time rust prevention never works because it plugs drain holes. If it isn’t done at the factory on each panel before assembled, don’t do anything later except oiling. No car is designed not to rust and are only designed to squeak by minimal rust through warranties and mandates.

You will have to tell me what cars are made completely of aluminized steel in body panels that rust around fenders, rockers and quarters and when they started doing it. It’s news to me. I know of no one who makes cars out of rust free materials other then a few exotic cars. They use the material in a few systems where mandated like exhaust systems and around some safety features.

In our area and I bet yours, after about 8to ten years, ever car ever made will begin to have examples of rust holes and rust perforation. Hyundais are no exception. In your high rust areas, your 09 is due for a rust out or bubbling in the next couple of years and the treatments I mentioned are your only options.

Manufacturers today commonly use galvanized steel along with rust inhibiting coatings, bonding where welding used to be, designed-in drainage, and ventilation of what used to be closed cavities. Besides that, robotic spot welding is used now instead of seam welding on much of the body panels, which avoids the HAZ (heat Affected Zones) that were prone to rust.

As tester said, undercoating is intended as a sound deadener, not a rustproofer. There hasn’t been a need for aftermarket rustproofing for perhaps 20 years or more now.

Manufacturers have been using aluminized steel for years. Here’s why.

When you order a piece of sheet steel you have options on how it’s preserved from when it’s milled to the the time it’s delivered. In my case I ordered it pickled in oil so it wouldn’t rust. But even with that over time the steel would rust if it sat on the shelf long enough. We weren’t building cars but instead prototype test fixtures. So not too concerned about the appearance.

Auto manufacturer’s order aluminized steel. The coating prevents the steel from rusting if sheets are dragged across each other, if they’re stored for extended periods of time, there’s no oil to worry about, and you can weld on it.

So if you’re building something that has a very nice paint job that’s exposed to the environments, you’ll use aluminized steel.

If you see rust on a vehicle, ask the owner how often that they wax the body.


I am still not following you. Are you talking about a steel alloy that includes aluminum in the alloy or a coating to prevent rusting prior to forming the sheet metal into body parts. You are under the mistaken impression that cars rust from the outside because they weren’t waxed ? I have to ask you where you live…if it’s a place where cars rust, it has nothing to do with wax jobs. It has to do with the steel rusting from the inside where the seems hold water and salt and rust occurs. Not amount of waxing can help, no amount of “aluminized” steel has, have you ever seen a rusted car…we do here all the time in cars less then seven to 10 years and it has nothing to do with wax on the outside. I think I am talking to people who either don’t live in high salt areas or buy new cars every five to eight years…"if you see rust on a vehicle, ask the owner how often they waxed the body ?"
The aluminum coating may slow down the rusting prior to manufacturing and to help rust prevention through mandates but it will still rust in much less then 10 years when exposed to salt…

There hasn’t been a need for aftermarket rust proofing"
There absolutely has…they stopped doing it because it promoted rust by clogging the drain holes . Plastic has been added to a lot of body parts as well, especially inner fenders…but the metal still rusts !!!

Do you remember hot dip galvanized steel?

Aluminized steel is a hot dip process. Only instead of using zinc they apply aluminum.

Because you can’t weld on a zinc coating.


You may like what you are hearing. But when you listen to this advice not to do anything, please remember this conversation in a few years when your well waxed car begins to bubble from the inside out from rust and later rust holes big enough to put your fist through happen. Just remember dagosa said told you you had to work at maintaining a rust free car. ;((

So @tester… You are telling me cars no longer rust when exposed to salt from the inside out…that this process and a good coat of wax is all that’s necessary ? You need to tell that to my best friend who has rust holes in his rocker panels of his seven year old Subaru…his well waxed seven year old Subaru.


Maybe I will recommend rustproofing even at 2,009, 30,000. Northern Ohio is a place where rust doesn’t sleep. An unperforated car at ten years old may be something you can sell or trade. Even if selling is a losing proposition You might at least avoid terminal ugliness as well as body repairs.

The article states that rust is less of a concern. CR test cars out to less then ten years and cars do well in most areas of the country without salt past ten years. We are talking about heavily salted areas.
It is a big concern if one, you want to keep your car past eight years or two, you don’t want any indication of rust up to that time. Heavily salted areas kill many cars in less then ten years and literally cut their trade in worth dramatically of any rust damage is observed in less then this time. When cars were traded in less then five years, it is seldom a problem. It will be with OP who plans on keeping his car much longer.
Is it still your contention that cars rust from poor or lack of wax coverage on the outside ? Just asking. :wink:

No need with today’s vehicles to rust proof or undercoat.

I live in the snow belt of New York State and my cars get brutalized by heavily salted winter roads. I have a 2004 Sienna with 175,000 miles that has never been rust proofed. I have some rust underneath the vehicle and I am just starting to show signs of spot rust in one or two places but nothing you can see unless you look very closely. I am pretty sure my van will die a mechanical death long before it rusts out. Just keep your vehicles washed in the winter, especially at a car wash that uses a car underspray, and wax once or twice a year. Save your rust proofing money for a vacation.

I guarantee that those little rust spots are just the tip of the ice berg and 1/100 of what is actually going on if they did not start as a neglected scratch and started from underneath or between body panels. I guarantee also, that those " little " rust spots have immediately removed hundreds if not thousands from your cars trade in value or resale. If all people want to do is have their car become a worthless rust bucket in less ten years in salted areas, then just sit back, drive through the car wash using recycled water by the way and think you have done everything you can. You play right into the car makers hands. Personally, I want my cars perfectly rust free for twenty plus years so when I trade them at 8 to 15 years, the next owner knows he is getting a solid rust free car with many years of use left. That’s where the savings is. That’s where the real maintenance is. That where the safer older cars come from.

Toyota makes some of the most reliable cars ever made mechanically that are prone to rust as rapidly as some of the worst cars made.

Outside of heavy salted areas, it’s less important. But in, it takes routine, yearly inspection and maintenance. I have never met so many people who are willing to change their motor oil worthlessly more then scheduled on motors that will last 250k miles regardless, then drive their purring engine powered cars to the junk yard with rust holes throughout. This happens all the time in my area and other salted areas as well.

Personally, the other day I was sickened to see a 2003 to 2005 model year, I couldn’t tell exactly, 4Runner, just a year older then mine or the same or less, with rust perforations around the rear tailgate window. The water back drains there when ever you lift the gate and is very difficult to treat. I have to face that as my frame and everywhere else has the appearance of a much newer car and rust free. Manufactures have you coming and going and rust is their devoted and trusted friend, guaranteeing repeat sales to repeat customers who keep thinking cars are somehow, magically, rust free until trade in time. What a hideous joke they play on all of us.

Thats why steel is the perfect material for manus,back in the 70s when the price of steel headed for the stratosphere the manus made some halfhearted attempts at visible rust proofing,while galvanizing helps,its just a sacrificial process-thats only good while there is still electromotive material in evidence,BTW,rusting can be eliminated with the proper electronic device,but heirloom does not drive the capitalists engines-Kevin