Rust between welded car panels.

[Rustedtruck]

Hello. I enjoy working on cars with the little time I got on my days off, be it mechanical, detailing, or metal work like looking for rust spots to fix. I recently bought a 2010 Matrix and have been looking for rust and trying to stop its spread. However, there are these couple of spots that I don't know how to deal with because the rust seems to originate from behind two welded panels. Any suggestions?

 

[Rustedtruck]

That is around the hatch frame on the inside and those bolts are for reinforcement I guess but the panels are welded.

 

[beltfeed]

It's 15 years old, be happy if it runs. If that amount of rust doubles in another 15 years, it will still look better than a 10-year-old car in the rock salt northern states.

 

[Rustedtruck]

I actually have turned it a project car. It was originally meant to just be a beater as my son's first car but me being me had to go and start mending and tinkering.

 

[racecougar]

I'd spray it with FluidFilm and let it creep.

 

[theoldwizard1]

I'd spray it with FluidFilm and let it creep.

FluidFilm is good, but you need to repeat every couple of years.

Some people swear by 3M Cavity Wax

 

[Kaizen]

jeez.......pretty sure if i showed you a pic of any of my cars you'd lose sleep. When those two panels were spot welded it started rusting. Without doing some deep surgery to get to the root, Its not worth the effort. Maybe scratch and seal it with a rush converter and some paint will make you feel better.

 

[racecougar]

FluidFilm is good, but you need to repeat every couple of years.

Some people swear by 3M Cavity Wax

Agreed that it's a better product, but it carries a much higher price tag. I did use it on a few builds, but switched to FF, as FF doesn't need to be reapplied often at all when used in cavities that don't see any real water/salt intrusion (the vehicles I'm working on don't go out in bad weather anyway).

 

[Rustedtruck]

FluidFilm is good, but you need to repeat every couple of years.

Some people swear by 3M Cavity Wax

Seems like a great product but if this seeps in between the two panels with the rust still there since i can't separate them wouldn't the rust keep spreading. I would have to get rid of that rust in-between first.

 

[Rustedtruck]

jeez.......pretty sure if i showed you a pic of any of my cars you'd lose sleep. When those two panels were spot welded it started rusting. Without doing some deep surgery to get to the root, Its not worth the effort. Maybe scratch and seal it with a rush converter and some paint will make you feel better.

I would like to remove the rust but I'm not sure that's possible now unless I start cutting or taking panels apart which is not worth it.

 

[Firebrick43]

Corrosion needs three things

Moisture

Oxygen

And an electrolyte

Fluid film or wool wax(I prefer since it doesn’t smell as bad) will keep all three from reaching the existing rust.

Even if it doesn’t stop it completely it will slow it down to the point that the vehicle will be worn out before it becomes an external visual problem of applied with some frequency

 

[racecougar]

Bingo.

You can either cut the car apart and likely make things worse, or you can cut off the air/moisture from the rust with something like FF to prevent it from getting any worse.

 

[jack stand]

FluidFilm is good, but you need to repeat every couple of years.

Some people swear by 3M Cavity Wax

On his apparently "interior" type panel(s) that are not subject to road spray from the tire area it should be fine for much longer if not almost indefinitely.
The creeping action is real and the hotter the weather at application, the better it will migrate between these mating surfaces that are very common since frameless cars are hundreds of little pieces of formed thin metal all spot welded together.

 

[Rustedtruck]

I'll go ahead and do a touch up on those two areas without clogging up where the panels meet. Then I'll use either fluid film or 3M cavity wax in that crevice. Now comes the part where i turn a decision into most likely hours of research and where a storm starts brewing in my mind trying to decide which of the two products last and works best.

 

[CraigStu]

How about splashing the area w/ one of the rust remover/convertor liquids. Find one that is thin like water and see what happens. Then do the FF.

 

[finn]

At the most, spray a bit of Fluid Film or WaxWool on that cosmetic “defect “.

Trying to “fix” it otherwise will destroy the factory paint bond and make it worse.

If that’s all you see after 15 years, it will still be fine in another thirty years from a structural standpoint. That’s really nothing compared to a three year old car in the rust belt.

 

[zendriver]

Scrub that rusty edge with a small wire brush, loosen the two bolts a bit, pry up enough to spray in some matching touch up paint.

Tighten the bolts, touch the area up and move on with life.

If it ever looks like it's rusting again - repeat. Rust work is mitigation, which can be good enough.

"why bother" just seems silly, IMO

 

[yellowbox]

Well yeah it is rust , but it is so so minor it will never amount to anything
Are you that worried about it ?
Have you ever seen a 15 year old michigan or new York or Pennsylvania vehicle?

 

[Wrench97]

The only way to totally get rid of it would be to separate the panels, treat it, weld it back together and repaint it.
It will probably only rust again only faster, clean off what you can and cavity wax it if it ever rots all the way through then you can cut it open and weld in new metal.

 

[Lorydr]

How about splashing the area w/ one of the rust remover/convertor liquids. Find one that is thin like water and see what happens. Then do the FF.

I 2nd that. Easy enough, with good results.

 

[drmarkr]

What is this "rust" stuff you speak of...??

 

[toplessHO]

What is this "rust" stuff you speak of...??

beat me to it

 

[BlindViper]

that's not rust that is patina

 

[zendriver]

that's not rust that is patina

^yep

15 years, that not bad rust.

 

[NYBODYMAN]

Hate to say it but that's normal. I get your OCD though. I would just leave it and run the **** out of the car.

 

[Glemon]

I would be jumping up and down celebrating my good luck if I bought a 15 year old car that looked that clean. As others have said, the car will die long before so.etbing like what is shown becomes any kind of issue. If it makes you feel better spray some WD 40 or PB Blaster on it and wipe it with a rag and I bet most of the runoff oxidation on top of the paint disappears.

 

[Bert_]

That's not rust. This is rust.

 

[toplessHO]

That's not rust. This is rust.

easily fixed with an old license plate or 2

 

[Bert_]

easily fixed with an old license plate or 2

I used the sheet metal strap protectors that come on truck loads of steel.

 

[Rustedtruck]

The only way to totally get rid of it would be to separate the panels, treat it, weld it back together and repaint it.
It will probably only rust again only faster, clean off what you can and cavity wax it if it ever rots all the way through then you can cut it open and weld in new metal.

Not that I will do that but hypothetically speaking let's say I managed to do all that. Why would it rust again if the rust was sanded off then primed and painted?

 

[Wrench97]

The spot welds burn the primer off between the panels.

 

[Rustedtruck]

that's not rust that is patina

Good to know. I assume patina will become rust

 

[Rustedtruck]

The spot welds burn the primer off between the panels.

I see. I was worried for a minute there.

 

[toplessHO]

The spot welds burn the primer off between the panels.

most vehicles are dipped in ephos after they are welded for that reason
cant speak for OPs model

 

[Wrench97]

most vehicles are dipped in ephos after they are welded for that reason
cant speak for OPs model

After he fixes it I doubt he'll be able to dip it

 

[Bert_]

easily fixed with an old license plate or 2

The fix. Apparently I threw a piece of tar paper in under the carpet also.

 

[Jazz1]

Spray it with some rust converter, once that dries some Fluid Film or similar product. Both products will leach inside there

 

[andyvh1959]

FluidFilm is good, but you need to repeat every couple of years.

Some people swear by 3M Cavity Wax

I bought a case of Krown corrosion inhibitor spray cans, bought on Ebay. Each can is large and goes a long way. Krown is likely similar to FluidFilm and 3M Cavity Wax. I bought a used 2009 Ford Escape with low miles and applied Krown underneath on the front subframe (which is known to rot to failure), and all the other areas known to suffer corrosion issues. That was last October, and so far from underneath after this Wisconsin winter it looks like when I sprayed it. I also sprayed it inside the doors, rear hatch, fenders, hood, etc. I had my 2019 Kia Sorento treated by a local Krown supplier before I had bought the Escape.

 

[theoldwizard1]

Krown is likely similar to FluidFilm and 3M Cavity Wax.

I don't know anything about Krown.

There is NO SIMILARITY between FluidFilm and 3m Cavity Wax. FluidFild is a lanolin (from sheep) based oil. Exposed to water, it will wear off is a couple of years. The 3M stuff is a "wax". Like stays longer than FluidFilm.

 

[Jacko264]

Bet there is more rust under the vehicle