Rust opinion: to cap or not to cap?

[NicksTj]

Hello, new member here.
Wondering if I could get some input from the experts. Inside of my TJ frame is a bit rusty. I’ve already capped the rear trailing arm on driver side but now I’m wondering if I should go ahead and do the skid plate center section.

I cut the bottom section out to replace the inserts due to rust getting the best of the surrounding metal. I treated the interior with POR15 after a good wash down and descaling of the bigger stuff.

Think it’s bad enough to go ahead and cap or should I continue protecting what’s left with fluid film?

 

[pagrey]

Caps and frame rust are such a gray area. What you might find great somebody else might shit a brick about. Your last photo looks like there is good steel there so maybe it'll be good but you're not going to find experts here, just allot of opinions. Not much real experience with caps or broken frames, more like allot of, "I'm comfortable with this or that based on thoughts and feelings." My advice is get it to somebody that welds steel, allot of steel, they will know.

 

[NicksTj]

Caps and frame rust are such a gray area. What you might find great somebody else might shit a brick about. Your last photo looks like there is good steel there so maybe it'll be good but you're not going to find experts here, just allot of opinions. Not much real experience with caps or broken frames, more like allot of, "I'm comfortable with this or that based on thoughts and feelings." My advice is get it to somebody that welds steel, allot of steel, they will know.

Ah yes. You are right about that, mixed reviews everywhere.

Well, I’m open to opinions anyway. I’m not really looking for the whole “frame swap it”
I don’t have a garage for that, I do all my work on my gravel drive way which is a pain in itself. I’m just 24 trying limp it by till I close on a house so I can really dig deep into a frame swap.

I was thinking myself that I could just go ahead and cut the bad out, clean the good metal at the top side where the caps would be welded and that’ll hold her over for a couple more years.

I was able to weld a flat piece of stainless back into the area I cut out with new inserts installed for the skid plate. If that’s doable I could definitely weld the good metal at the top. Just wondering if it’s even bad enough to worry about safe t caping now or if I could stop the rust where it’s at.

 

[Wingback73]

Top and sides look fine. Coat it, weld a bottom back on, and enjoy it. It'll last you long enough to get your feet under you and do the frame swap if you so choose

 

[fourpointzero]

After doing what @Wingback73 says, then keep it coated with Fluid Film. And wherever you have access holes to the inside of the frame, coat it with FF using a wand. They sell a kit with a wand. It'll hold you over till you find the time and money to swap or do a proper cap. But ALWAYS keep it coated. Thats means every FALL for WINTER and touch-ups a long the way. Even summer time.

 

[NicksTj]

I do appreciate both inputs.

I guess I left out a bit of information. I wouldn’t be lazy man capping it.
I actually have both left and right side center skid plate safe t caps sitting in my building.
I’d just like to keep an original frame as long as possible if it’s not in questionable condition.

It’s POR15’d right now but I’m sure a good 1/8 to 3/8 of it got burned off when welding on the bottom half and nurserts.

Here’s a picture of fluid film oozing from my frame. I’m familiar with the product and I bet this was in there for a good 3 months with frequent washes after wheeling. Good stuff.

 

[Vtx531]

I dont think it is bad enough to do it now. Can probably get another 10 years before it needs it

 

[bromel]

I'm not sure I follow, here. You've already cut the bottom off. You've done the hard part, so why not just install the caps and forget about it?

 

[Wingback73]

If you already have the caps, and need to weld a new bottom on anyway, then you should just use the caps instead. You'll get a much longer lasting outsome. Use the opportunity right now while the bottom is off to spray some phosphoric acid all over the inside to convert the existing rust to iron phosphate. Keep it wet for an hour or two, then wash it out with plain water and let that dry. Paint with a rust inhibiting paint. Weld on your caps, do your best to re-coat the inside, and you'll have at least another 10 years before you need to do the frame. The big thing, given the existing condition, is to convert the current rust to iron phosphate, which is inert. To be clear, water doesn't cause rust, salt does, so don't be afraid to wash out the inside after letitng the phosphoric acid sit for a couple hours to do its job.

d-

 

[Mike_H]

If you already have the caps, and need to weld a new bottom on anyway, then you should just use the caps instead. You'll get a much longer lasting outsome. Use the opportunity right now while the bottom is off to spray some phosphoric acid all over the inside to convert the existing rust to iron phosphate. Keep it wet for an hour or two, then wash it out with plain water and let that dry. Paint with a rust inhibiting paint. Weld on your caps, do your best to re-coat the inside, and you'll have at least another 10 years before you need to do the frame. The big thing, given the existing condition, is to convert the current rust to iron phosphate, which is inert. To be clear, water doesn't cause rust, salt does, so don't be afraid to wash out the inside after letitng the phosphoric acid sit for a couple hours to do its job.

d-

Water will most certainly cause rust .. Have you ever left a raw piece of steel out on a humid day? It will start rusting very quickly.

 

[fourpointzero]

I think what @Wingback73 meant is that once you hit the metal with phosphoric acid, rinsing it with water shouldn't be a concern. Least that's what I deduced from it. But leaving it exposed long enough, for sure will result in rust. But the acid certainly mitigates it for some amount of time. Thats been my experience when using products with phosphoric acid.

 

[Wingback73]

Water will most certainly cause rust .. Have you ever left a raw piece of steel out on a humid day? It will start rusting very quickly.

Yes, of course, from a chemical perspective that is a true statement. From a practical perspective, the reason vehicles in the North rust while those in other parts of the country don't is the salt, not water. Otherwise vehicles in Seattle would be the worst in the country. As would Florida given the afternoon showers.

I was trying to convey a lack of concern about washing off the acid. If the OP does so and let's it sure dry it'll still be fine.

 

[Yoda]

Save it. Go to POR-15's website and check out their Marine Clean and Metal Prep. The Marine Clean is a strong degreaser and the Metal Prep dissolves rust and leaves a phosphate coating to prevent future rust.

Eastwood sells a good frame paint to spray the internals of the frame and keep it protected. Use POR-15 on the outside of the frame.

Someone mentioned Fluid Film. That's not a bad option but I've also heard really good things about Cosmoline RP-342. It is a petroleum based wax that will wick into the tiniest places and lasts a long time. It is used in the Military on just about everything that is metal to keep it protected and prevent rust. It comes in an aerosol can, spray it everywhere and make sure to get it inside the frame.

 

[jeepguy03]

From what I can see it doesn't look too bad yet, but keep in mind rust is always easier to deal with before it gets out of hand. If it were mine I would at least clean up the rust and coat everything as a preventative before closing up the bottom.

 

[NicksTj]

For clarification I only opened up below where the skid plate sits, not the whole bottom half of the frame.

Upon further inspection I do believe I’ll cap it this coming week. It’s pretty thin in certain areas. Under the tub the sidewalls of the frame have small pin holes that blow through with a small tap of a hammer.
I’ll clean the scale off with a flap wheel when I get it cut open and treat the whole frame front to rear.
Thanks for all the information on the rust prevention lads. Been a issue I’ve been chasing for awhile now, since I owned my Tj for 2 years. Started with the rear trailing arm.

I’ll post a couple pictures from that event.

 

[DEValken]

For clarification I only opened up below where the skid plate sits, not the whole bottom half of the frame.

Upon further inspection I do believe I’ll cap it this coming week. It’s pretty thin in certain areas. Under the tub the sidewalls of the frame have small pin holes that blow through with a small tap of a hammer.
I’ll clean the scale off with a flap wheel when I get it cut open and treat the whole frame front to rear.
Thanks for all the information on the rust prevention lads. Been a issue I’ve been chasing for awhile now, since I owned my Tj for 2 years. Started with the rear trailing arm.

I’ll post a couple pictures from that event.

View attachment 315743

View attachment 315744

View attachment 315745

Yeah, that's some scary stuff right there. One speed bump from a bad afternoon...

 

[NicksTj]

Yeah, that's some scary stuff right there. One speed bump from a bad afternoon...

Indeed.
It’s patched up now and solid there. I about flipped when I first seen it.