How Do I Treat Rust Inside Wheel Wells?

Hey everyone,

I was surprised to find in the wheel wells on my 71 that there may be some light surface rust starting. The shop that did the restoration a while back apparently used undercoat on the inner wheel wells and it finally is peeling off.

Would the right way to go about fixing it be to sand the light rust off and then just re-coat it with undercoat? Or should I take it to professionals since this is a high quality level restoration that my impatient hands probably shouldn't touch? Don't want to ruin a near perfect car.  I've done practice body work on a shitbox 90 Cherokee but obviously I didn't care if I botched anything on that

:thankyouyellow:

Hey everyone,

I was surprised to find in the wheel wells on my 71 that there may be some light surface rust starting. The shop that did the restoration a while back apparently used undercoat on the inner wheel wells and it finally is peeling off.

Would the right way to go about fixing it be to sand the light rust off and then just re-coat it with undercoat? Or should I take it to professionals since this is a high quality level restoration that my impatient hands probably shouldn't touch? Don't want to ruin a near perfect car.  I've done practice body work on a shitbox 90 Cherokee but obviously I didn't care if I botched anything on that

:thankyouyellow:

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Cheapest way is to handle it and stabilize is ye old WD-40.  Kept my wheel well rust at bay for years...

Ouch. WD-40 will contaminate any surface you'll want to paint in the future; don't use it. Instead, sand until the rust is gone, then spray with epoxy primer. Then put on the undercoat. Epoxy primer (good ones, that is...) will act as a sealer and pretty much keep rust from happening underneath it.

A temporary protectant is ospho (found at Home Depot/Lowes). Spray on the sanded surface and let dry. It may result is a white residue, but will keep the surface free from rust for 1-2 weeks. It is readily removable with water, oil/grease remover, etc. Used until you are truly ready to paint a more permanent cover.

Another thought would be to use a product from Eastwood or POR 15 and follow the manufacturers directions.

Thanks, Jay

If the undercoating is peeling off after only a couple years, it was either the original undercoating, or they simply sprayed over the existing rust. The best thing to do is to get in there with a small scraper to try to remove as much of the loose undercoating as possible and see the extent of the problem.

If you have holes, then you'd probably want to visit a body shop.

If it's all solid metal and just surface rust, you can sand off (and a wire brush on a drill) the majority of it, then treat with a product such as Rust Bullet's Metal Blast. It will dissolve the remaining rust and leave behind a zinc phosphate coating, which is an excellent rust inhibitor and adhesion promoter. This gives you an excellent base for a rust inhibiting topcoat (Rust Bullet, POR15 etc) and then a couple coats of high quality undercoating to blend everything in. I used POR15 on the wheelhouses of my 71 and it has seen plenty of car washes, plus it's sat outside for several occasions in the rain when I needed the garage space. No rust - 16 years and counting. 

Some after, before, and during pics of the frame on my '07 Silverado using the Rust Bullet system.

https://www.amazon.com/gp/product/B001BPY8FG/ref=ppx_yo_dt_b_asin_title_o09_s00?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B000HDMUDU/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

I think I will be able to easily sand off the light rust by hand, I got a closer look and its just starting. I'll scrub off all the old undercoating/rust and then treat it with the mentioned products. I just wish I had a lift, I'm going to have to remove the rear wheels and do it with a jack, yikes. Will an aerosol can of undercoat work for this situation?

Obviously some others know the coating products better than I.  I also did not fully understand your problem.  If the surface rust is on a wheel facing surface in the wheel well then I agree with others that you can clean it real nice, prep it properly and protect it with a good coating.  I thought you had rust surfacing in the lip area where the inner butts with the quarter skin.  My WD-40 suggestion was for protecting that tight area from inside the trunk where you could never get it clean.

Now I have to ask, why would you use undercoat on the wheel wells?  Is this car your daily driver?  Do you see a lot of harsh weather?

Undercoating has inherently been a rust promoter with age versus a protection.  Yes, it sprays on easy, has good sound deadening properties and is a pretty good rock and chip protector.  The problem is it dries and hardens, then cracks.  Once it cracks, moisture penetrates the cracks and begins seeping and getting trapped between the undercoat and the painted metal.  Mix that concoction with a little salt from the mid-western winter roads, and Shazam!  you have a mess of rusty metal in a few years.

So think about what you need in the wheel wells.  The bodyman who refinished mine used a thin, low profile spray on bedliner for the "undercoat" surfaces on my car.  It is a very durable and chip resistant coating that has a texture like undercoating, but will not turn brown with age and is easier to clean.

The POR 15 mentioned by others is well known as a durable chassis coating that stays black also.  

So, think again before using undercoat.  If it is what you want to do, I would say a rattle can of the stuff is just fine so long as the surface is prepped properly.

Good Luck!

Share pictures if you can.  That always helps!

kcmash

Most of the spray can stuff is not good - if you want to use the spray cans, the best one is available

at the local Ziebart dealer. It is a bit pricey.

Most of the spray can stuff is not good - if you want to use the spray cans, the best one is available

at the local Ziebart dealer. It is a bit pricey.

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Agree about Ziebart as a great undercoating. I have a 1971 Mustang Sportsroof, originally from Pennsylvania and it is a very solid car.  Would not have lasted at all if not for the Ziebart rust prevention which was applied when sold new by the new car dealer.  Just try and find an old car originally sold up there!

As for a good converter-sealant, I like Rust Bullet.  Haven't used but all on here who have used raved about it.

Ray

Best way to cure rust is ...Never park near a Lancia...metal maggots can jump  

Undercoating in the wheel wells acts to protect the metal from the high speed projectiles coming off the tires. Sand, rocks, bits of other cars etc. You need some sort of protection or you have badly chipped wheel wells and rust starting in no time. You also need to do the underside of the tops of the front fenders.

IMO, sand it, treat it, seal it with paint and then apply whatever rubberized material you prefer. You should be good to go for a long time.

Like Kcmash stated, I also used a Bedliner product called Raptor on my wheel wells (inside and out), cowl/dash area, the interior side of floor pans, lower inside of quarter panels, and trunk floor. Rust prone areas I knew I would be covering up with something else later. I then applied sound deadener over the raptor in wheel wells, quarters, cowl, etc to give it a more factory texture and appearance. On the trunk floor, I applied the stock spatter paint over the Raptor. The floor pan was covered with matting and carpet.

My understanding is POR15 needs rust to chemically bond to. It should not be applied over light rust or clean bare metal. Also, POR15 is not UV resistant.

I have not used it but Eastwood makes a spray on rubberized rust encapsulator, they claim "can be applied directly over rust and without the bubbling that creates air pockets thus trapping rust undercoating that also has their rust inhibitor in it."

The is the Raptor bare (with some paint overspray on it) before I covered it up with sound deadener, etc.