Minor floor rust repair

JHZR2

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I donned more PPE and went at it with a grinder and wire wheel. The wires are pretty firm. I pushed down as much as I could, essentially trying to see in the limited space, what was solid and what wasn’t. I found that most of it didn’t get better. It is firm, reasonably solid, and doesn’t really grind down any more. Where there was lose material, I pushed through it and ground back to firm areas where material no longer was easily removed.

It doesn’t look a lot different than the first few minutes. I think I need some tiny roloc discs to fit in the small spaces where the rust is.

I’m also thinking that perhaps I should shape to the exterior of the vehicle, grind the paint underneath with a grinder and/or vacuum-attached sander, and have a much larger, broader area to bond to. Then I can also patch to the topside if I choose. Essentially a fully sealed metal sandwich. I think I’ll get to bright metal easier underneath. It’s fully accessible.

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I actually consumed a few wire brushes, but couldn’t progress any further. They don’t scuff to bright metal I guess.

Red scotch brite also couldnt cut enough to get it bright.
 
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Iff that was my truck and I really wanted to keep it, I’d be replacing the floor pan. JMO
 

JTK

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I see several mentions of replacing the floor pan and I don't doubt that's part of the job here. Thing is, from what I see in the pics, the rust is well into the rocker panel and door frame structure. That's a different ball game I would think.
 

JHZR2

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I see several mentions of replacing the floor pan and I don't doubt that's part of the job here. Thing is, from what I see in the pics, the rust is well into the rocker panel and door frame structure. That's a different ball game I would think.
It’s not. It ends at the vertical metal that holds the door seal. The rocker is solid and ends before the rust area. This is why you can actually see the ground through the holes I’ve abraded. The rocker is boxed underneath and is solid on all sides. The floor pan is just that, and sits on the frame, no other structure. The floor pan metal underneath has a few small rust bubbles associated with what you see above, but is not overly compromised. This is why I think it will be a good concept to grind the paint underneath to bright metal and actually adhere the new sheet metal from underneath. It will save significant effort cutting and trimming to meet the size and features of the floor pan from inside, and will allow a more substantial contact area. I would but it right up to the boxed rocker area in the area that the rust exists, and seal the entire area (which is the beauty of the epoxy).
 
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JHZR2

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Not great photos, but the holes seem here are the ones Inmade from the top. The rest looks good and is solid. Thinking I’m better off putting metal underneath.

Maybe to get the pressed features I do need to cut the patch from a floor pan, versus beating other sheet metal??

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JHZR2

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beyond time to pull out the seats, carpet and padding to see what's really going on there...
I’ve pulled the seats, pulled up the mat, and put the truck up against deluges like mad. Both natural rains of a few inches, and hoses spraying every last spot including the windows, cowls, doors, chmsl, etc. all dry. I know the AC drains properly.

Neither door had a vapor barrier for a number of years. Water came in readily from that. The seam along there is also where salt and slush from boots would settle. I don’t think it’s any more than that.
 

JHZR2

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I tried some 36 grit on a wheel. Seems to get to bright metal quick for a second, then not much else. I think the little 1” wheels that fit load up too quick.

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I think most of this metal is solid-ish, though it might be Swiss cheese once ground the whole length.

The only area that needs new metal is the strip that is flat along the edge. I can cut it out, but I think the epoxy approach is better. I’m thinking to grind to bright metal from underneath and apply/epoxy the new metal from underneath.

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I would just continue to the rear, epoxy inv to bright metal.

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What I don’t know is how to do the bent areas. How do you form sheet metal to match the profile? I guess this is why some would say to get a floor pan and cut it all, so those features might match up?

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Features along the bends and features like that.

how would one form to that sort of a profile?

Im thinking that 20-22ga from HD would be my best bet for most of that long straight area. Epoxy it bright to bright, then treat the old metal on the inside with ospho or similar, seal, coat/paint. Then both sides are encapsulated in epoxy/paint.
 

JHZR2

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beyond time to pull out the seats, carpet and padding to see what's really going on there...
Also, I pulled the other side and it’s solid. Complete. Even the underside has no surface rust or bubbles. Both sides had no vapor barrier, the driver side surely had more salt and other exposure to other junk.

@Trav, any thoughts on if an epoxy repair from the underside, which would be easier to cut/grind paint to bare metal is acceptable? I’d think I have better control over the metal to metal seal, any top coating, and how the interior is finished, doing it that way, versus leaving an exposed overlap seam on the exterior of the vehicle. Thanks!
 
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You will never be able to match those contours with a piece of flat sheet metal, moreover, the contours provide structural rigidity. Buy an outer floor pan, trim it to overlap into solid metal then attach it however you wish.
 

JHZR2

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It can be done but it takes skills/equipment and a lot of time and patience, definitly not a youtube job. The best thing is to buy a pre formed piece and fit it in.
Ok. I’ve found a number of suppliers of the full outer half of the floorboard. Can I just cap the spots where there are holes, essentially grinding to bright metal and epoxy if the new part with a complete overlap to the existing? Seems that it would be strongest that way. If I cut out the metal, the overlapping section would need to be bent inward and an amount of overlap would need to exist anyway. I’d think more overlap would be better (I.e. a cap), versus that.
 
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Scrub it with Ospho and the red scotch brite pad top and bottom.

The fiberglass Laminating epoxy I linked. saturate 5 layers of 6 oz fiberglass cloth/ tape and it will be as thick or thicker than 18 awg steel.
Prep the steel properly for maximum epoxy adhesion and it will never come off.

Say you greased it intentionally preventing adhesion, and still laid the fiberglass saturated epoxy over it, you'd have a perfect mold you could drive rivets or screws through,l but properly prep it and the glass is unlikely to ever separate from the etched mechanical toothed steel.
Fiberglass sandwich top and bottom.

With the rust encapsulated in epoxy you will easily get to 500K miles. I've got way worse rust, osphoed, encapsualted with epoxy and fiberlgass in much higher structurally stressed areas, and don't even think about them anymore.

Get the Ospho. Ace Hardware.
Likely want to soften the undercoating with acetone and a rag then Ospho it.

24 hours later, you'll understand.
Have a cheap chisel and a vacuum and then more Ospho on a scrubbie.

If you had the welder, and the skills and the time and the new floor pan, then by all means.

I could spend a day and use less than 30$ Ospho, Epoxy, razors, masking tape and fiberglass and have that solid, encapsulated and more than good enough for half a decade.

I'd spend a few days applying Ospho and chiseling blackened rust first. LAther rinse repeat.
Just get the Ospho.

Dont wast any more time with mechanical abrasion until you apply the Ospho, unless it is a cut off wheel and you just remove it all.
 
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Ok. I’ve found a number of suppliers of the full outer half of the floorboard. Can I just cap the spots where there are holes, essentially grinding to bright metal and epoxy if the new part with a complete overlap to the existing? Seems that it would be strongest that way. If I cut out the metal, the overlapping section would need to be bent inward and an amount of overlap would need to exist anyway. I’d think more overlap would be better (I.e. a cap), versus that.
You could do that but it is a haven for rust between the two panels. Cut it out to good metal all the way around as much as you can, the real bad spot you can leave a larger overlap if you don't want to cut that part.
Cut enough out only so the metal is rust free then cleanly and straight cut a piece of the new panel about two inches larger all around and lay it in, this is more than enough overlap.

Clean the metal that is the overlap on both pieces well with an angle grinder and coarse grit flap wheel then drill some small holes about an inch in and 2 inches apart through the new piece, these will help getting the self drilling 1/4" hex head sheet metal screws in easier.
Clean all contact surfaces with IPA and wipe it down then apply the epoxy.
Lay the new piece on the epoxy and immediately start putting the screws in all around the new piece, use a power driver to speed things up you don't have much time.

Let it cure (I just leave it overnight) and remove the screws, grind off any excess and fill the screw holes and entire edge with tiger hair or short strand waterproof filler (do not use "bondo" it is talc based and absorbs water). Finish it smooth and use an epoxy primer, you can then coat the whole area inside and out with Napa stone guard 4004 (black, the 4003 is white) This stuff is incredibly tough, it will not chip and nothing will get under it. I have used this on a properly prepared steel wheel wells and it remains in perfect condition after 12 years including winters.

If you need more info PM me, I don't follow threads very closely.

 

JHZR2

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Scrub it with Ospho and the red scotch brite pad top and bottom.

The fiberglass Laminating epoxy I linked. saturate 5 layers of 6 oz fiberglass cloth/ tape and it will be as thick or thicker than 18 awg steel.
Prep the steel properly for maximum epoxy adhesion and it will never come off.

Say you greased it intentionally preventing adhesion, and still laid the fiberglass saturated epoxy over it, you'd have a perfect mold you could drive rivets or screws through,l but properly prep it and the glass is unlikely to ever separate from the etched mechanical toothed steel.
Fiberglass sandwich top and bottom.

With the rust encapsulated in epoxy you will easily get to 500K miles. I've got way worse rust, osphoed, encapsualted with epoxy and fiberlgass in much higher structurally stressed areas, and don't even think about them anymore.

Get the Ospho. Ace Hardware.
Likely want to soften the undercoating with acetone and a rag then Ospho it.

24 hours later, you'll understand.
Have a cheap chisel and a vacuum and then more Ospho on a scrubbie.

If you had the welder, and the skills and the time and the new floor pan, then by all means.

I could spend a day and use less than 30$ Ospho, Epoxy, razors, masking tape and fiberglass and have that solid, encapsulated and more than good enough for half a decade.

I'd spend a few days applying Ospho and chiseling blackened rust first. LAther rinse repeat.
Just get the Ospho.

Dont wast any more time with mechanical abrasion until you apply the Ospho, unless it is a cut off wheel and you just remove it all.

I have Ospho. I’ve used it before. It was my intention to use it at the end on any exposed metal/leftover rust on the interior, prior to prime/paint.

The opportunity here is to epoxy a repair panel. This is a new(ish) legitimate approach, and not terribly different from hard curing paint/patch. My biggest concern is how do we get to the right amount of bright metal overlap/overlay given the small area, small holes, etc. because the area is pretty small, an inch here and inch there results in more or less the entire area. The issue @Trav brkng up about too much overlap being an opportunity for rust is valid. I’ve seen that with fiberglass repairs over holes in old MB diesels. Sometimes these patches with fiberglass will fall out because they get undermined. That was part of the reason why I was interested in capping it from underneath. More surface area that can be easily taken to bright metal, the ability to heavily seal it and observe it from inside, etc.

So, you’re saying to ospho first. Are you implying that it will “lift” a certain amount of metal that is the remnant rust in pores and other spots? I had thought to do it last, but it’s simple enough to start laying some down right now...
 

JHZR2

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Some of the things in here struck me as odd, like using stranded filler on bare metal instead of 2k epoxy primer first on the bright metal... and improper application of the adhesive per the 3m instruction to do three coats and prime both sides to get full corrosion protection... but they use adhesive with scab plates, which I think will be a best bet for me to do spot repairs. I’m hesitant to cut the whole floorboard out and then encounter issues. Probably should rent or invest in a mig welder, but if the patches are small, I can get the product on all surfaces, the epoxy binder is the corrosion inhibitor, and will protect everything as a first layer.

I think I’ll template everything with painters tape, then Manila folders or thin metal flashing, then finally with 22ga sheet metal.

 
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Scrubbing the whole area with Ospho will help reveal where there is unknown rust under the paint that is not visible. It will clean the whole area and help prepare for adhesion.

Ospho being the same viscosity of water can creep into rust that no wire brush can ever hope to access. It will help to reveal any soft rust that would best be removed, before being encapsulated. On super rusty areas you can watch the metal soak up the Ospho like thirsty wood. Ospho does not evaporate.
Rust you previously thought was ready, will prove to be easily removed

After scrubbing and 18+ hours passes, you will see some white powder, which easily brushes off, but also where there is rust under the nearby paint you were previously unaware of. With the 1/8"chisel and wire brush you can easily lift this paint and even remove the Blackened rust back to brown rust and if scrubbed again the rust will get smaller and the grey etched steel will grow. The paint might discolor slightly but will remain intact except where rust has creeped under it.
This process can be repeated until there is NO MORE Rust, just pitted etched steel that is ready for extremely good adhesion of whatever product is placed atop for bonding/encapsulating the formerly rusted steel.

If this grey etched steel is properly encapsulated, the rust will not return.
If this etched prepped steel is further gouged with new sharp sandpaper, or razor blade for additional mechanical tooth there is little to no chance that rust can creep in from the sides and lift the fiberglass, and multiple layers of fiberglass cloth/tape pulled tightly can be as strong or stronger than steel and easily conform to the surface undulations.

Do not compare crappy old repair jobs that used fiberglass matt saturated with polyester resin, with properly prepared steel and fiberglass saturated with properly ratioed and thoroughly mixed Epoxy resin. Epoxy has many times the bond strength and is much more flexible.

Scrub it with Ospho, give it time to work, come back and turn blackened rust brown with a chisel and wire brush, then scrub it again with more Ospho.

A few lather rinse repeats of this Ospho scrub/chisel process will yield not only a better idea of the true extent of the rust, but also help one to more effectively repair it and prevent its return.
 

JHZR2

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Scrubbing the whole area with Ospho will help reveal where there is unknown rust under the paint that is not visible. It will clean the whole area and help prepare for adhesion.

Ospho being the same viscosity of water can creep into rust that no wire brush can ever hope to access. It will help to reveal any soft rust that would best be removed, before being encapsulated. On super rusty areas you can watch the metal soak up the Ospho like thirsty wood. Ospho does not evaporate.
Rust you previously thought was ready, will prove to be easily removed

After scrubbing and 18+ hours passes, you will see some white powder, which easily brushes off, but also where there is rust under the nearby paint you were previously unaware of. With the 1/8"chisel and wire brush you can easily lift this paint and even remove the Blackened rust back to brown rust and if scrubbed again the rust will get smaller and the grey etched steel will grow. The paint might discolor slightly but will remain intact except where rust has creeped under it.
This process can be repeated until there is NO MORE Rust, just pitted etched steel that is ready for extremely good adhesion of whatever product is placed atop for bonding/encapsulating the formerly rusted steel.

If this grey etched steel is properly encapsulated, the rust will not return.
If this etched prepped steel is further gouged with new sharp sandpaper, or razor blade for additional mechanical tooth there is little to no chance that rust can creep in from the sides and lift the fiberglass, and multiple layers of fiberglass cloth/tape pulled tightly can be as strong or stronger than steel and easily conform to the surface undulations.

Do not compare crappy old repair jobs that used fiberglass matt saturated with polyester resin, with properly prepared steel and fiberglass saturated with properly ratioed and thoroughly mixed Epoxy resin. Epoxy has many times the bond strength and is much more flexible.

Scrub it with Ospho, give it time to work, come back and turn blackened rust brown with a chisel and wire brush, then scrub it again with more Ospho.

A few lather rinse repeats of this Ospho scrub/chisel process will yield not only a better idea of the true extent of the rust, but also help one to more effectively repair it and prevent its return.

Good stuff, thanks! I’m going to start this tomorrow with the ospho that I have. That includes a few other minor bubbles on the rocker. If I need to patch that I will as well.
 

JHZR2

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Scrubbing the whole area with Ospho will help reveal where there is unknown rust under the paint that is not visible. It will clean the whole area and help prepare for adhesion.

Ospho being the same viscosity of water can creep into rust that no wire brush can ever hope to access. It will help to reveal any soft rust that would best be removed, before being encapsulated. On super rusty areas you can watch the metal soak up the Ospho like thirsty wood. Ospho does not evaporate.
Rust you previously thought was ready, will prove to be easily removed

After scrubbing and 18+ hours passes, you will see some white powder, which easily brushes off, but also where there is rust under the nearby paint you were previously unaware of. With the 1/8"chisel and wire brush you can easily lift this paint and even remove the Blackened rust back to brown rust and if scrubbed again the rust will get smaller and the grey etched steel will grow. The paint might discolor slightly but will remain intact except where rust has creeped under it.
This process can be repeated until there is NO MORE Rust, just pitted etched steel that is ready for extremely good adhesion of whatever product is placed atop for bonding/encapsulating the formerly rusted steel.

If this grey etched steel is properly encapsulated, the rust will not return.
If this etched prepped steel is further gouged with new sharp sandpaper, or razor blade for additional mechanical tooth there is little to no chance that rust can creep in from the sides and lift the fiberglass, and multiple layers of fiberglass cloth/tape pulled tightly can be as strong or stronger than steel and easily conform to the surface undulations.

Do not compare crappy old repair jobs that used fiberglass matt saturated with polyester resin, with properly prepared steel and fiberglass saturated with properly ratioed and thoroughly mixed Epoxy resin. Epoxy has many times the bond strength and is much more flexible.

Scrub it with Ospho, give it time to work, come back and turn blackened rust brown with a chisel and wire brush, then scrub it again with more Ospho.

A few lather rinse repeats of this Ospho scrub/chisel process will yield not only a better idea of the true extent of the rust, but also help one to more effectively repair it and prevent its return.
I’ve been doing the ospho bit, red scotch brite really doesn’t remove much, but I don’t want to be too aggressive either. At some point I’ll want to get the underside to bright metal to epoxy in the new floor patches.

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