Use a weld through primer, but clear it out of the bottom of the hole before you do the puddle weld.
Use a weld through primer, but clear it out of the bottom of the hole before you do the puddle weld.
You're out of your element, Donnie!
Panels rust at the seams, pretty much without exception. The act of welding them together ruins any possible coating that could have prevented it.
Keeping moisture out is the primary preventative measure. Most OEM seam sealing is inadequate, leaving gaps and let's moisture get trapped in bad spots. Generally, the hardest to reach spots are where you need it the most. So being thorough helps.
A lot of people advocate weldable primer on the panels before mating/welding, and I've done it both ways but I've never lived anywhere rust was really an issue, so even on the very few cars I've taken back apart I've never seen much more than light surface rust one way or the other.
Even with the weldable primer, welding still burns it off around the weld, so like I said above, they pretty well always rust.
Providing weep holes, and eliminating pockets that can collect sediment (where applicable) probably isn't the worst idea while you have it apart.
However, that can still be like propping a chair against the front door to keep undesirables out. Sometimes the door just opens the other way.
Oh, and you're in this deep, just part those two panels.
But, but the marketing department says the weld through primer stops rust! Marketing never lies!
Jokes aside I get what you are saying. Stopping rust completely is impossible, just do what you can. That weld through primer I linked claims to be full of aluminum or aluminum oxide or some such, which they claim rises to the surface of the weld puddle, forming an aluminum oxide coating that prevents corrosion of the weld.
No idea if it works, as the company’s own marketing is saying that, but that’s the reason aluminum bronze alloy doesn’t corrode, the aluminum forms a coating of aluminum oxide which stops the copper in it from corroding. Not a bad idea anyway, probably better than nothing.
I’m not planning to drive this in salty winters anymore, that’s probably the #1 way I’m going to prevent rust in the future.
I'd totally be lying if I said I knew what was in weldable primer, but that stuff in particular sounds like a gimmick. I'm used to the zinc based stuff, which I'm pretty sure doesn't have any aluminum in it. I don't know why you would want to introduce aluminum into your weld. I'm similarly suspicious of the "copper" weld through stuff.
I'm personally not a fan of weldable primer as I usually get crappy looking welds or even inclusions/porosity. (Although, on edit, it occurs to me this might have to do with the fact 99% of my welding is done with flux core wire.)
Not to say that it can't be remediated with some tweaking of settings and adjustments to techniques, but I usually end up feeling like I'm burning through a poorly prepared surface.
All that said, I'm considering using some kind of weld through when I split the rockers on Uncle Ben, but I'll be sticking to 3M or SEM zinc based stuff if I do.
Again, I'd use this where you don't see the repair, forget welding, this is the way collision shops do it now:
You'll need the gun and the mixing tips but this stuff kicks ass.
You'll tear the metal before you break the glue joint.
I've heard about that stuff, that might be the ticket. I wonder if that means I could plaster a whole part in POR-15 and glue it together without worrying about the weld torching the protective coating.
Is there a way to non-destructively disassemble something after it's been bonded with that adhesive? (I don't think there is.)
I would certainly take that into consideration for a "permanent" vehicle that's likely to be difficult to find collision repair parts for in the future.
Alternatively, this might be a good opportunity to experiment with building tubular front support structures. 
With some removeable inner fender Wells and whatnot.
#dzusallthethings!
Crackers said:Is there a way to non-destructively disassemble something after it's been bonded with that adhesive? (I don't think there is.)
I would certainly take that into consideration for a "permanent" vehicle that's likely to be difficult to find collision repair parts for in the future.
1: Heat
2: It's a GMC van...
In reply to Trans_Maro :
It's a Ford van, Of course your point still stands.
Good point about removability in the future, i hadn't thought about that. I do indeed plan to keep this thing forever, might be good to think about servicability. I'm sure there will be some opportunities to utilize that glue if not this front corner. Tubular support structures with removable this or that might be a good idea for FAR future me, sounds pretty awesome but maybe a bit extreme at this point 
Don't overthink this stuff. If you do a reasonable job of getting the rust off where you can see it, and coat the part such that it wont get wet, it is going to outlast you. You have enough work to do that you don't need to get hung up with analysis paralysis.
I restored the tin on my GT 25 years ago and will admit that not a lot of thought went into sophisticated perpetual rust avoidance. Cause no internet, no money and no clue?
The GT still looks good and no signs of new rust from the repaired areas.
Pete
Pete is a lot more concise than I am. LOL
Good point, I just like overthinking things. I got plenty to remove and patch before I can do any painting.
speaking of keeping water away, there’s a place where a bunch of leaves built up and formed a compost pile, I think there’s a pic on page one. I don’t see rust looking in the flap, but I think the bottom panel is one of the fender liner parts. If I remember correctly, it’s the same panel that forms the drivers side floor and it’s rotten along the edge. I think I’ll try to remove that whole panel, that way I can get the rust and look up into that compost chamber and see what to do about that. It almost looks like crap in there ran down the seam to where it’s all rusted out in the floor.
The last steel tool i touched in my garage stuck to my hands. It's a bit cold out there. I'm doing some planning and shopping for a garage heater.
Someone showed me this:
I usually detest fiberglass plastered all over, but that van on the bottom, is that a nifty designed extractor hood on an econoline? I think it is! Don't know if that design is amazing, ridiculous, pointless, stupid, or just plain bad, but it's definitely multiple of those things. Looking top down it appears like the entire engine is behind the hood:
The only thing sticking out is the serpentine belt, all the pulleys, and the fan. I doubt an extractor hood would help or even be useful, but it made me think a minute. Not about anything i'm going to do, just bench racing/building in my brain. Looks like the shape of the hood just in front of the extractor part would 'motivate' air through the extractor, too... Moving on to something i'm actually planning on doing...
The fender liner is steel, made in 2 parts, and rust has formed where they join:
The front panel goes up to the front of the body, while the rear panel makes up the driver's side floor. The two panels join directly above the wheel.
I was thinking about the "brackets and bolts" idea from Crackers, it looks like the front panel in that fender liner mounts to a bunch of stuff in the front corner, so if that wheel well liner joint is where i make the split, (and maybe split the panel above it too), it would remove everything in the front with minimal complication. By this I mean the body. Everything mounted inside those panels would need to be addressed, but that's for future planning to solve. Also I would have to figure out how to change 2 of the fender bolt locations. Even the bracing between the front part and a body mount connects to the front wheel well liner part only:
Here's where the wrench gets thrown into the situation... That side-on picture above, you can see the rear panel i'm talking about which makes up the floor, it has a hole in it. That's fine. In front of that the panels makes up the bottom of a trap that collected leaves and created a compost pile. You can see the plastic flap there. A cubic foot of compost, rich black compost, came out of there. I think water in there started corrosion in one of the flanges, that ran down and caused the floor to rot. I thought "Fine, i'll just remove that panel, fix the rust, and get up into that compost chamber and fix that". If you look, it's a huge panel. HUGE. It also goes under what appears to be a support frame for the body.
Looks like I won't be removing it, but I WILL be cutting into it. That'll be fun. Should I make a removable panel at the bottom of that compost chamber? It would help me clean it out in the future and potentialy fix more corrosion if it shows up later. Obviously I'll have to cut out a bit of the floor and weld on new metal, too. Fortunately that whole support frame thing, which is above the body mounts, looks fine and i'm perfectly happy to leave it alone. This is good news since I can't remove the body from the frame anyway. There appears to be a rubber grommet filling a hole in it:
I assume this is from the undercoating, since they filled stuff with tar, too. If i feel the need to fill the thing with more rust stopping tar or wax or whatever the cool kids are using these days, i'll have access, so I got that going for me, which is nice.
also made a tear down video:
Found some interesting stuff... photos are up to date, video is behind.
In reply to Crackers :
When you said tubular frame and removable panels, is this what you meant?
Because I like it! Not gonna go that far in this van, but maybe a future project...
Trap door doesn't sound like a bad idea. That rubber flap exit path is certainly not working well, and not easily accessible. A small removable panel in the wheel well attached with screws would be easy to make.
After looking over the pictures again, having the entire radiator support removeable for service probably isn't very feasible here. It probably wouldn't be easy to do without pulling the fenders first.
I think I'd just cut that rusty spot out and put in one big patch and weld it all together.
If you can resolve the drainage issue you will likely never have to deal with it again.
Oh, and that plug is a factory thing. That hole probably served some purpose during assembly and they just plugged it to keep junk out.
Rufledt said:In reply to Crackers :
When you said tubular frame and removable panels, is this what you meant?
Because I like it! Not gonna go that far in this van, but maybe a future project...
Something like that. It would probably be underwhelming in the van because of packaging, but the idea was more utilitarian for the sake of access for engine maintenance.
Crackers said:
After looking over the pictures again, having the entire radiator support removeable for service probably isn't very feasible here. It probably wouldn't be easy to do without pulling the fenders first.
The method I thought of would be less of an easy-removal situation and more of a “have to do it in the shop and it would take an hour minimum” situation, but it would allow me to remove a bunch of stuff that is currently (until the drilling started) welded solid. Also it would probably take two guys because it would be very heavy... and the hood wouldn’t come off with it. And I don’t know if the front bumper would get in the way, since it’s attached to the frame and not the front of the body. And I would probably have to pull the grill and fenders. It’s not a perfect plan.
Yeah, that sounds about right.
If you plan it right, you should be able to strap the core support to a hand truck and move it while attached to the hand truck.
An absurd person could even add pick-up points so as to bolt it to the hand truck.
Ok a little more progress. I did some cleaning up here for no reason other than it was so covered in dirt and tar and stuff i had no idea what the steel actually looked like:
Turns out it looks pretty good. THen i removed whatever this is:
I assume a vacuum chamber thing since it's just a sphere with a vacuum hose going to it. No idea what the other end connects to, i didn't bother trying to figure out either. There are vacuum lines all over, i just labeled what hose went to it.
Next up, remember the hood:
That's a gross patch i tried to do when i was a teenager. It didnt' work, obviously. It's a shame to lose the patina that i remember from my entire life (it always looked bad is what i'm saying) but break out the power tools:
The skin is pretty terrible, the frame was mostly gone in that spot. However, before i cut the frame part out, this happened:
The hood frame is pretty simple in that area, pretty much straight with a straight almost-90-degree bend, though not a sharp one like you would get from a metal brake. I marked where I wanted the patch, made the patch, then cut out along a trace of the patch i made. Then I cleaned everything up around the weld joint and started trying to weld it in:
Remember, I am VERY new to metal work and welding, so this is going to look bad. I blew a few holes trying to figure out some settings, but I think by the end (most of the welds along the top line) i had it worked out mostly. You'll notice it's not perfectly straight, but im assuming as long as the patch fit properly and the butt welds were flush, i could try and straighten that crease afterwards.
I don't have all the overlapping tack welds, but I ran out of time. Weekends are also play with the kids time, so i went outside, played on the snowy swings with my almost 4 year old and watched her make faceplant snow angels. According to her, if you lay face down when making the snow angel, the angel will have a face. These are things I never thought about when I was young. I just now realized she wanted to read "The snow queen" before bed tonight. That story is quite long, longer than her attention span it seems, but I guess snow is on her mind. In other news, my 1 year old is NOT a fan of the snow blower. The sound, heard through the closed front door, made him quite unhappy...
Anyways, I also have questions. Speaking of overthinking the rust prevention, i'm assuming patching this frame is straightforward, but what about the skin? along the weld joint in the skin, i can clean the outisde of the original steel but not neccessarily the inside, which is still covered in primer and in some places tar undercoating. Where the skin folds over the frame, it appears ford added seam sealer. Will that screw up a weld if i try to butt weld a patch over that? I tried finding videos of people fixing skins, but they all appear to be doors where they can reach inside, I can't on this hood. Also they tend to be quite vague on the details. in one case, the guy butt welded the large patch onto the skin, welding all the way across the surface, but when it came to the folded over part, he just showed folding it over. He mentions he's going to weld that so there isn't a cut line, but never shows the process. He also doesn't appear to have seam sealer to deal with.
I would assume a weld through primer or perhaps some other product should be put on the frame before i fold the new skin over it, any suggestions? This isn't a section of skin that is spot welded on, just folded. Find some seam sealer like ford did?
Here's an underside shot:
In the weld joint, the gaping hole on the left is my mistake, i blew through it. I have a copper backing thing now that i used to fill some of the blow-through holes, but like I said i ran out of time. The hole on the right is the drain (which i will have to re-drill now that i filled some of it with a patch). When cutting of the skin on the far left, I accidentally cut through the hood frame. What should I do there? Weld the skin patch up, fold over, and forget it? Cut more skin off, being more careful, and weld up the cut? The skin patch will be equally plain, just a rectangle with a straight, not very sharp crease, then folded over. the edges of the panel are basically dead straight, this is a van after all, and if i get it wrong a bit the factory panel gaps are so bad nobody will notice.
Made a video of the first cutting/drilling/brushing away of the rust if you're interested:
One last question, the weld through primer or other stuff people paint in interior panels before they weld stuff up(open to suggestions there), does it work in Wisconsin winter temp? Or am I going to be looking for a garage heater?
Both sides of your weld have to be stripped.
Yes, weldable primer on the inside after stripping is a good idea.
Practice welding through it on some scrap pieces to get settings/hand speed dialed in before welding on the actual work piece as it will have an effect.
Don't worry about the knick in the inner support. In reality, you're going to end up welding the inner/outer skins together anyway.
Seam sealer is a double edged sword here. Factory sealer probably went on before the two parts are assembled. You don't really have that option since you're MIG welding your patches in.
Since you can't apply sealer to the backside in any practical way, this would be a perfect example of a place to make some drainage holes so water can't sit in the crease and rot the front of the hood.
Just a few holes 1" wide and 1/2" tall situated just above the folded lip.
Straight lines on exterior panels are almost never dead straight. Even more rarely are they straight on two planes. Do yourself a favor and double check with a straight edge before you install the patch panel.
If applicable, I prefer to heat shrink slight crests in panels.
You can make larger radius bends with a brake press by stacking bent sheets on the top leaf. It does require a lot of tweaking on the brake though.
I'm no hope on the painting in lower temps. I've been putting off some painting projects because it's been in the 50's.
It probably won't matter for primer, but it will take forever to dry and may end up with a lot of surface irregularities.
Is that the new Eastwood stripper? How do you like it?
I've spot painted into cooler weather, 50-ish. Halogen work lamps 250-500W can throw some decent heat indoors. Warm the paint can too before spraying. Test surfaces w/ IR temp gun first to see if ya got the right temp. Leave lamps on after spraying to cure the paint.
edit: like these or similar
Ahhh yes, welding and seam sealer. The stuff IS going to try and mess up the bead since it will melt on the backside of the seam and get sucked up into the bead. But just like rust on the backside and gaps or holes, something that you just need to suck up and figure out.
What I do.
Use a torch to burn as much as possible right at the seam. Then I wire wheel and pick out as much of the burnt residue as possible
Go real hot on the welder. Seems to increase the odds of the bead digesting the gaseous emanations of burning seam sealer before it solidifies.
Stop and brush the soot off with a small wire brush between tacks. The seam sealer is going to keep making soot, so anything you do to reduce the stuff is a good idea. Since I am always welding on the front face of the last tack, I want this front face to be clean so that the new molten metal slides off , into the seam and solidifies. Also the reason I am going hotter is because I am letting this bead cool as I wire brush the soot off and I want a good wet puddle on the last tack.
I find that as you move along, things tend to get better as the welding heat is burning off the seam sealer ahead of where you are welding.
Pete
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