Remove Under-body Rust

[actionstan]

Hello All,

This is in regards to my 2013 KIA Forte, It has a few scuff marks where it looks like it has gone off the road and dragged against the front part of the sub frame when the previous owner had it, the spots are up by the tow hook.. (one of the spots its from me.. dont ask

)

I figure taking care of these sooner than later will help prevent it from getting out of hand since the spots are so small.. a few spots 3 inches in size or less.

KIA recommends to use a wire brush to remove as much surface rust as possible, then to spray the car with cavity wax filler, then rustoleum underbody coat. My local Home Depot has the underbody spray, but I am having trouble finding the cavity filler.

I have also seen things like the rustoleum rust converter, and to me it just sounds kinda gimmicky.. it turns rust into into a protective paint-able surface? If I did use a rust converter does it have to be covered? and if so should I just use black spray paint, or black primer?

Let me know your thoughts, and if you know of a better product, thanks!

 

[Falken]

Wait until Summer, and get the car up on 4 solid jack stands.

Buy 4 aerosol cans of Fluid Film (sheep's wool oil) and, on your back, using a flashlight, just spray the likely areas underneath well.

On newer cars I find it harder and harder to find anything that isn't already plastic, galvanized, or heavily painted already.

Just hit the worrisome areas well with Fluid Film.

Then, do this last, as it drips the most:

Attach the red straw that is taped on the can on the nozzle of the Fluid Film and open a door, and at the bottom drainage holes, slide the straw in so it is parallel to the interior door surfaces.

The wide spray will make a nice rainbow of Fluid Film inside the door, and get all your doors really well this way.

Doing this on a hot Summer day, or in the late Spring, gives the Fluid Film wax all Summer to melt and creep everywhere inside the doors.

 

[Donald]

The rust converter is not a gimmick, but phosphoric acid. Or naval jelly. It actually does work but needs some rust to work best. Typically after that is done and cleaned off with acetone you paint the area with POR-15 or Eastwood Encapsulator. Both of them provide a hard paint shell that oxygen/water cannot penetrate.

However if you can wirebrush off all the rust, that is best. Then a self etching primer and a topcoat.

 

[Donald]

Originally Posted By: Falken
Wait until Summer, and get the car up on 4 solid jack stands.

Buy 4 aerosol cans of Fluid Film (sheep's wool oil) and, on your back, using a flashlight, just spray the likely areas underneath well.

On newer cars I find it harder and harder to find anything that isn't already plastic, galvanized, or heavily painted already.

Just hit the worrisome areas well with Fluid Film.

Then, do this last, as it drips the most:

Attach the red straw that is taped on the can on the nozzle of the Fluid Film and open a door, and at the bottom drainage holes, slide the straw in so it is parallel to the interior door surfaces.

The wide spray will make a nice rainbow of Fluid Film inside the door, and get all your doors really well this way.

Doing this on a hot Summer day, or in the late Spring, gives the Fluid Film wax all Summer to melt and creep everywhere inside the doors.


Two comments:

1) CarWell or Krown last longer than FF
2) Any of the above need to be done yearly on areas subject to road dirt/mud/water/salt.

 

[slug_bug]

I've used the "rust converter" product. It seems to work well. Rust hasn't popped through in a little over two years. My areas were visible, so, I painted over it with auto touch up paint. For your application I would go over it with underbody coat.

 

[KrisZ]

I would forget the rust converter. This is what I used to remove rust.



It will only react with rust and is easily neutralized by water. After that I would paint with self etching primer, followed by either colour matched paint, or something like rustoleum.
Once everything cured for several weeks, I would use Fluid Film, Rust Check (that's your cavity filler) to fill inside the frame as well as to coat the scratched area. I would not use the asphalt undercoating because it is mostly useless and you will not be able to visually inspect the damaged area afterwards. You can also use plain old lithium grease and brush it on the damaged area.
Inspect every once in a while, preferably before winter to see how the coating holds up and re apply if necessary.

 

[Donald]

Originally Posted By: KrisZ
I would forget the rust converter. This is what I used to remove rust.



It will only react with rust and is easily neutralized by water. After that I would paint with self etching primer, followed by either colour matched paint, or something like rustoleum.
Once everything cured for several weeks, I would use Fluid Film, Rust Check (that's your cavity filler) to fill inside the frame as well as to coat the scratched area. I would not use the asphalt undercoating because it is mostly useless and you will not be able to visually inspect the damaged area afterwards. You can also use plain old lithium grease and brush it on the damaged area.
Inspect every once in a while, preferably before winter to see how the coating holds up and re apply if necessary.


What you show in the pic is phosphoric acid I am sure. Same stuff under a few names. Loctite Extend is similar also. But more of a one product "converter and protective coat".

Look at the MSDS.

 

[01rangerxl]

I haven't heard the term cavity wax before either, but it seems to be a European term for wax undercoating, such as Cosmoline.

It's not cheap...
http://www.cosmolinedirect.com/

 

[RobertISaar]

anyone who does any serious amount of soldering knows that flux is a very important part of the soldering process. the way it works is VERY similar/identical to rust removers/converters, it reduces the oxidized layer so that other work can be done(for soldering, the added metal to attach to existing components, for bodywork, so that the rust doesn't continue to eat through your car).

definitely not a gimmick, or at least there are non-gimmick products out there.

 

[bigjl]

We get KuRust over here.

Whitish fluid that changes colour to a black/blue colour when cured

I have used it to stop rust getting worse if i am not in a position to fix it properly

They do a gel aswell. But i have never used it

I woukd use any rust convertor you can find easily

Treat it now and then as above sort it out properly when it warms up

 

[bigjl]

Cavity Wax is a common product in the UK

The most common being Waxoyl

You buy it in aerosol form usually.

You inject it into enclosed parts of the body. Such as inside doors or inside box sections.

Very good stuff though it is an old product and therefore there are more modern ones around

I am getting the Pathfinder done next year probably. As it has a seperate chassis and there are odd bits of surface rust on it.

Dinitrol is also a big name in rust proofing in the UK.

Another big name is Ziebart.

Back in the 70s and 80s you would see Ford Escorts or Cortinas, performance ones like RS1800 or RS2000 or even a Lotus Cortina. And you would see them for sale with the term ziebarted from new.

There are a lot of good products in the UK due to our climate being a lot wetter and colder than a lot of the US.

And we had more Fiats and Lancias than the US has had i reckon so rustproofing has a long history!

 

[Donald]

The US still has Ziebart and had others awhile ago like Rusty Jones. But the car makers started doing a better job building the cars and many of these places closed up shop.

 

[supton]

If the rust is superficial, is there any real gain to erasing it and painting? Versus oiling it and reapplying said oil yearly? I mean, if you can't see the patch of rust normally, and if you have to oil coat yearly anyhow...? Or is the plan to not oil coat, just fix rust as it shows up?

 

[bigjl]

Think the US Ziebart was better than the stuff we had in the UK as when the product was released over here it was franchised I think

But even the second tier product we got here was good if you touched it up every year or so.