Rust on fender flare

Stock FSJ Tech Area
Post Reply

Topic author
69gladiator
Posts: 231
Joined: Tue Oct 15, 2013 6:10 pm
Location: stratford,ct

Rust on fender flare

Post by 69gladiator »

I have a reoccurring issue with rust on the top of the fender flare at the seam with the fender. Two years ago I cleaned the metal, shot two coats of epoxy over etching primer. I noticed that the paint is blistering again. Is there something that I’m missing?
Last edited by 69gladiator on Sat Feb 20, 2021 5:56 am, edited 1 time in total.

GrandW
Posts: 224
Joined: Mon Aug 20, 2018 6:19 pm

Re: Rust on fender well

Post by GrandW »

At a high level, and with little detailed knowledge of your situation, generally 2 things could have happened. The rust wasn't completely removed, and thus came back. Or the paint that went over it didn't like something and it's not rust, but the different paints not playing together. Since you used primer, that generally creates a barrier between paints to eliminate that issue. Again, take this with a grain of salt given the variability of the situation.
1987 Jeep Grand Wagoneer
User avatar

Stuka
Site Admin
Posts: 11789
Joined: Thu May 12, 2011 5:53 pm
Location: CA
Contact:

Re: Rust on fender well

Post by Stuka »

It could be coming from the seam between the fender and the flare as they are two pieces of metal.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

rocklaurence
Vendor
Posts: 2565
Joined: Sat Mar 30, 2013 6:53 am

Re: Rust on fender well

Post by rocklaurence »

Is it the front or rear flare? Next time clean it/remove the rust then apply automotive seam sealer. Youll want to tape off the area and remove the excess with Lacquer thinner. Then repaint. Make sure that there isnt water debri trapped behind the rust

Topic author
69gladiator
Posts: 231
Joined: Tue Oct 15, 2013 6:10 pm
Location: stratford,ct

Re: Rust on fender flare

Post by 69gladiator »

Sorry , I miss typed and attempted to immediately edit. The rust occurs on top of the flare at the fender seam. I been told contrary things about using seam sealer on the joint. Some claim that if water get behind the sealer, it will never dry and speed up rust/rot. I’m wondering what everyone has used for a rust neutralizer. I’m thinking if it’s thin enough, it may flow into the seam.

rocklaurence
Vendor
Posts: 2565
Joined: Sat Mar 30, 2013 6:53 am

Re: Rust on fender flare

Post by rocklaurence »

Chances are that if its at the top that there isnt moisture on the inside of the panel and its from exposure to the outside. Using seam sealer will eliminate the pits/gap to collect dirt and moisture. OEMs use it to protect the seams. :shock:
User avatar

tgreese
Posts: 7118
Joined: Fri Jun 08, 2012 6:31 am
Location: Medford MA USA

Re: Rust on fender flare

Post by tgreese »

There are a couple of kinds of "rust neutralizer" that I know of. First are chemicals that change the oxidation state of rust from red rust to black oxide. The best known of these is "naval jelly" which has phosphoric acid as its active ingredient. I would not use this, since it would be hard to get all traces of the acid out of the seam after the rust was "neutralized." Note this is not a sealer - red rust is bad because it expands as it forms, and lifts away, exposing fresh steel. Black oxide forms a compact coating on the steel which stops the rusty progression. Black oxide is only modestly resistant to new rusting.

There are newer products that affect the same chemical treatment to the rust and remain behind on the surface, like Permatex rust treatment. This product contains an organic rust convertor with some kind of latex base that also seals the surface. I have used this and it works well.

The other type of rust treatments are paints, typically a moisture-cured urethane with some impermeable pigment, often called encapsulators. This material takes up any water in the surface when it cures and incorporates it into the urethane matrix. The pigment overlaps like shingles to seal water and oxygen from the surface. There are plenty of such products - I like and use Aluthane which I buy direct from Epoxy Products in NH.

Whatever you put into the seam, it should be a product that seals the seam and is impervious to air and humidity. Polyester body filler is the worst, since it uses fine talc as the bulk component, and this is permeable to both oxygen and water. When used for body work, you depend on the top coat to seal out the elements. Seam sealer is meant for filling and sealing seams, though again, the top coat should be intact on both sides of the joint.

There are easily dozens of ways to approach this. Most shops would use new parts and not put the rusty fender back on the car. With restoration, you have to use your head and decide what's going to be good enough. If there is rust in the seam, the only repair that will last as long as the original part is to take the seam apart and clean out the rust down to bright steel, then put the seam sealer back, and seal to the elements with primer and top coat.
Tim Reese
Maine beekeeper's truck: '77 J10 LWB, 258/T15/D20/3.54 bone stock, low options (delete radio), PS/PDB, hubcaps.
Browless and proud: '82 J20 360/T18/NP208/3.73, Destination A/Ts, 7600 GVWR
Copper Polly: '75 CJ-6, 304/T15, PS, BFG KM2s, soft top
GTI without the badges: '95 VW Golf Sport 2000cc 2D
Dual Everything: '15 Chryco Jeep Cherokee KL Trailhawk, ECO Green
Blockchain the vote.

sansabarJ
Posts: 152
Joined: Sun Jun 16, 2019 1:40 pm

Re: Rust on fender flare

Post by sansabarJ »

Ok , as a longtime car truck restorer and too much !! Experience with RUST... It's a big problem that's hard to really solve for the long term . That's not to say it cannot be controlled or eliminated but the latter is not totally realistic given the age of these trucks . I've used Rustmort , Loctite RUST stop and many many other products . Most do little or no stoppage of RUST unfortunately .
Yes ,as said here it is the flair to body or bed seam where the flair is spot welded to the body or fender or bed . This IS the RUST area as is the seam RUST issue . You would have to remove the flair and blast the areas clean ,and or new metal if needed . Treat the clean metal and follow up with appropriate primers that can be welded thru . I however found and use ONE STEP spray RUST stop product .
It has a polymere coating in it that SEALS the metal . It is a RUST convertor that turns RUST black
And seals the air from the surfaces to stop oxidizing = RUST. This is really good product and I've used it all throughout my 72 J4000 where needed with great results . Best product so far that really works . I believe Loctite now offers a similar product that does the same . ONE STEP can be bought at auto body supply shops ,not auto parts stores . It's commercial grade .
Wire brush and also scrape out the seams really good and spray the product into the seams .
CAUTION : mask off any areas so the coating does not drip down onto areas not desired .
It is like an acid convertor spray that creeps into seams . Very thin consistency. You can use a little brush to help work it into the seams . About 17 bucks a can and goes along way . Apply multiple passes into seams or on any area to be converted. 1st coat let dry about 20 minutes or go over again and so on . The RUST will turn black when it's converted , bare metal will be grey when coated . I want to also note that seam sealers and other products , including top coat paint can introduce moisture into the metal and cause RUST. One trick I did with the ONE STEP nozzle was to drill it out for a WD 40 or carb spray straw to give a more forceful spray into seams . You want to get it deep into seams. That's my seam advice to everyone on RUST and body seams and flairs . I had to I stall an NOS AMC bed panel that I bought to replace a badly dented panel on my bed . Once it was off and all spotweld drilled out , it had normal RUST between the panel and bed.
This bed looks RUST free , but there's always RUST....It seems ...pun

SansabarJ

Topic author
69gladiator
Posts: 231
Joined: Tue Oct 15, 2013 6:10 pm
Location: stratford,ct

Re: Rust on fender flare

Post by 69gladiator »

Since I last posted, a body shop owner told me to use Rust Mort. It’s available from body shop supply houses. I also have been told by an old body guy to use seam sealer. My brother was also told to use seam sealer. I think that’s probably the worse thing to do. One pin hole in the sealer and it will never dry out.

SJTD
Posts: 1924
Joined: Tue May 21, 2013 12:02 pm
Location: Lompoc, Sunland or somewhere between

Re: Rust on fender flare

Post by SJTD »

Doesn't matter what you use to treat it, convert it or remove it, then coat it and seal the seam with. If there's a path for moisture to get to the area from the back the rust will continue and lift the paint.

Had a rusty spot on my hood sitting out in the weather against the fence. On a whim I wire brushed it a bit to remove the dust. Still nice and rough rusty red. Worked in some plain ole interior latex house paint. After a couple years the paint was dull but hadn't lifted. Still hasn't but but the wife made me put it inside so mice didn't use it.

Morale is you have to exclude moisture.
Sic friatur crustulum

'84 GW with Nissan SD33T, early Chev NV4500, 300, narrowed Ford reverse 44, narrowed Ford 60, SOA/reversed shackle in fornt, lowered mount/flipped shackle in rear.
Post Reply