"bondo" got caught in the rain, what next?

I was doing a little "bondo" work on a project I have. Well I didn't get it finished before it got too dark to see so I stopped for the night. Problem is, that was Friday. Pretty much been raining around here since then. The car is sitting out in the rain. SO...

Is the "bondo" that has been exposed to the rain still Ok or do I need to grind it out and start over again? The effected area is only about 6" wide and about 24" long and is covering a weld seam. The area was bare metal before the filler was applied and where the filler has been sanded back to bare metal is still clean (no surface rust visable.) Whadda ya think? Gene

 

Don't know for sure but I understand your concerns. Considering it will absorb moisture from the atmosphere I reckon you may be screwed. Sorry I don't have enough bodywork knowledge to say fer sure.

Good luck with it

Pete

 

Bondo's cheap, don't take a chance! That shit'll absorb water faster than a sponge, AND hold it longer!

 

If you haven't sanded the "skin" off yet you are probably OK. Just dry it out real well, maybe with a heat lamp.

You shouldn't think that just putting primer on it will be much better, though. Water will soak through primer, too.

 

I've always wondered, if moisture can get into primer and bondo on a wet day, can it also escape on a dry day? or is there some magical thing that traps it inside forever?

 

Shouldn't a primer/sealer be put down before the bondo to protect the bare metal? I recall reading that advice somewhere. I'd check this out with the pros first. Is there a Customer 800 number on the can? Call them, it's their stuff, they shoud know. Or ask a local (reputable) body shop.

 

Bondo has to go on bare metal, no primer on the metal 1st, and you gotta rough the metal up 24 or 36 grit disc 1st. I don't know how wet it got at Your place, but it sounds like real wet, so grind the stuff off and go again. Doc

 

Bondo can go on bare metal or over good primer, it's not that picky....but like you say, do some grinding first to give it something to bite into.

 

http://www.jalopyjournal.com/forum/showthread.php?t=8318

good bondo tech.

sand that 'chit off and try again.

 

Wrong; bondo can be & in fact it's best to apply it over epoxy primer (but ONLY epoxy primer - no other primer or paint). 50Dodge4x4 if you had done this I'd say dry it out good & continue. But since you're over bare metal I wouldn't chance it. Grind it out & redo it bondo is cheap.
~ Paul
aka "Tha Driver"

Giggle Cream - it makes dessert funny!

 

Bondo can be put over epoxy. But if you intend to gain bite or adhesion over using it on bare metal, you won't. The best use of bondo over epoxy is to use a good quality epoxy with a good solids content (not the current DPLF stuff). The metal needs to be properly prepped for the epoxy primer which should be cured and free of solvents and sanded for mechanical adhesion of the filler. It's extra work and time and production shops don't do it. Working on newer cars the steel usually still has the factory phosphate coating on it for corrosion protection. Working on old rusty panels is shakey at best. Epoxy primers do not nuetralize or convert rust. Most of todays epoxy primers are lead and chromate free which greatly lessens the effective corrosion protection and moisture resistance. Epoxy primers work best at corrosion protection if you metal etch and condition the steel or re phosphate the surface. If you want epoxy, do some checking for an epoxy that will do what you need as far as protection and compatibility with your topcoat system.

overspray

 

hey overspray--I read with interest your post from a year or two ago (linked earlier in this thread) about all I ever needed to know about fillers...great info!

but I still wonder, is there something magic about filler or primer that traps moisture such that it can't escape? seems to me that a warm dry environment would allow the moisture to leave the same way it came.

I'm talking about the case where the filler/primer was applied in a dry environment, but later exposed to rain or high humidity not the case where the metal was wet to start with.

 

I think the mud and/or primer would dry out fine, but if the water had time to oxidize the metal underneath, the damage is already done. If you got some bondo wet and then dried it out, you could grind it down and it wouldn't have any moisture inside, but the metal behind it may have already been oxidized and then you'll have problems. Depending on conditions it might be OK, if it was only a day or so it'd probably be fine, but do you want to take that chance? I think that's the point everyone's trying to convey.

 

That make sense...

things sure are different here in the desert, my suburban has been sitting in the shop for several years after I sandblasted it and doesn't have rust yet, just bare gray steel.

no, there are no houses for sale in this area.

 

the moisture will be trapped between the metal and the bondo. something about it yes the bondo will dry out but it traps just enough between the two to cause problems most likely way down the road. there is something about it that makes it harder for the moisure to escape than it was for it to get in. we had a guy that did the same thing as you my first year of auto body class(i did 3 1/2 years the last year and a half as teachers aid). the teacher told him to grind it all out and start over and then took a practice panel put filler on it and soaked it with a hose for a full class period 4hrs. let it sit used a heat lamp to dry it quick but no good. we cut the panel into and ou could see a layer of corrosion between the metal and the filler.

basiclly say all is lost grind it out and redo it or it WILL come back to haunt you later...ken....

 

The way I do it is the way Gene Winfeild taught Me how to do it, bare metal, bondo, prime , paint, that's the way We did it at Gene's and We never have problems that way, and I'm to old to change now. Doc

 

those of us who are incompetent (speaking only for myself here) need to go back and fix low spots we find after we get the primer on.....

 

Yup, you guys got it right. Some of the fillers in bondo are like a sponge as in talc, the mineral in talcum powder. Most people that do filler work use it like it was meant to be, worked in a short period of time, then primed or sealed for protection. The thought behind using epoxy under bondo is generally for a moisture barrier. The problem is that the epoxy has to be nonsoluable to moisture and there are no primers or paints that are totally resistant to moisture, with the possible exception of some new NASA coatings ( I'm pretty sure we have a couple space engineers on the H.A.M.B.-I know we have lots of "space cadets"). Some primers/epoxies have better moisture resistance than others. Picking a good one takes some research.
With today's safety concerns over lead and chromate, sadly our primers and paints have gone to hell in the durability and corrosion protection areas. Without lead and chromate the primers like "DP" epoxy are not the same as they were 20 to 30 years ago and do not offer the corrosion protection that the old formulas did. Some of you that use them may already know that a thinner rag will wipe them off or soften them. The styrene in bondo will definately penetrate them also.
The resin in bondo is the "stick" and most of the moisture resistance. Polyester resin is fiberglass resin as in boat resin.
Yeah, I wish I could do my bondo work in the desert also. Most of the time bondo works very well at normal temp and humidity ranges, which is where most chemists test their products-40% humidity @ 72 degrees F.
Bondo also has a powerful solvent in the resin-styrene- which is the smell we associate with it (bondo). You can smell styrene at 2 parts per million. Walk by a glass Deuce body on a hot day and you'll know it's not steel.
Styrene is very powerful similar to acetone and will disolve a lot of primers if used straight.
Go on paint companies web sites and read the tech info for different primers to help educate yourself. There's some good info available to help pick the products that will do the best job. Some even have info on the use of bondo with their products.

overspray

 

I agree with you on everything but a couple points. Bondo sticks and feathers better over epoxy - try it sometime. The current DP is great - although not as good as when it had lead, but I doubt you'll find anything with lead any more.

Nothing wrong with that; it was true in the past (bondo only over bare metal). Just now you can put it over epoxy & get better adhesion & feathering.
~ Paul
aka "Tha Driver"

Save the whales. Collect the whole set.

 

All that's been said about epoxy is pretty much on the ball, always listen to overspray!
You still can put your bondo over bare metal, but I think you get a bit more corrosion resistance over epoxy, since water can't penetrate it as easily, even without all the good stuff (chromates, lead...)
As for the epoxies, you really need to read the tech sheets. Some epoxies are made to be an adhesion coat, some for filling (surfacing) and some are primarily sealers. Not an expert with PPG, but I thought that DP-90 was primarily a sealer. Primers made for a specific purpose will not work as well if used for another! Some primers can have multiple attributes. I prefer to work with House of Kolor EP-2 or KP-2, both epoxies, both have ALL the above qualities, good as a first coat over bare steel, of fiberglass, excellent filling and sanding, and also good as a sealer. Bondo sticks to it very well, feathers out well, and it's a good sealer to keep bleaching of the hardener from bleeding up to the paint. I use it over bare steel, if I can't get to plastic work right away, or to seal it up, if I need to break from that job for a day or 2, it's very convenient!

 

A guy named John Hatton (the chemist who developed the resin formula for Rage filler) told me personally that there was no better adhesion of body filler to epoxy than to bare metal. He was concerned that if there were solvents still present in the epoxy primer when the filler was applied it could lead to a slight loss of adhesion or shifting of the filler/bondo on the epoxy primer. His reccomendation was to use filler on bare metal, properly prepared and cleaned. The best way to insure that most solvents are released from the epoxy is by baking at the reccommended temp and time for that specific primer. I'm sure everyone takes this precaution when putting bondo over epoxy. Most of the high quality body fillers/bondo featheredge very nicely on bare metal. Another concern is that the feather edge of the filler on top of the epoxy primer is thin and can let some solvent from the primer coat soak into the area of the epoxy ( most automotive epoxies will absorb a little solvent even when cured) at the feather edge causing a small amount of shift and swelling which could show up as shrinkage later on in the repair process. This occurs most often when you put the first coat(s) of filler primer (hi-build) on real wet. Lead is pretty much gone in most automotive products but some primers still have chromate. Lead and chromate have large heavy molecules that help make the primer or paint film more dense and resistant to penetration by solvents or moisture.

This is a good topic of discussion. One of my concerns about putting bondo over epoxy is hardly anyone says to what degree and how they prepped the bare metal before the application of the epoxy. You can put epoxy over rust just like you can put bondo over rust. If the metal is ready for epoxy it's ready for bondo. E P O X Y does not spell M A G I C. The key to both systems is product knowledge, good prep and technique. If you do good metal work and have your metal prepped, cleaned and sanded, you would actually get excellent results doing MINOR filling with bondo type skim coats/glaze over a good quality high build urethane primer filler. Truth be known, most new good quality body fillers/bondo will stick to any good clean dry surface. Tell me how easy it comes off your fingers after it sets. OEM (factory) paint cleaned and sanded will work even better than epoxy for bondo. The factory paint won't absorb solvents as easily as epoxy primer. You will actually have to grind it (bondo) off.

overspray

 

I have read and understand all the comments above concerning the use of epoxy or etch primer and then aplying the body filler over that.
It makes good sense to me as a preventive measure for corrosion resistance too.
I do have a couple of questions.....
Let say for example that the epoxy was applied a little too heavy or the drying conditions[or activator quality] were a tad off what is recommended......would that -then cause adhesion problems too?
what about a swipe of de greaser not adequately wiped clean?
I feel the ways suggested here is apt to result in loss of adhesion [in a lot of first timers] using these methods and products.

I CONFESS-I only use body filler over epoxy primer when the customer does the primer himself and then brings it to me that way.
If I do the prep work -I ALWAYS sand the metal clean then usually use a wire brush topolish any rust off -Then a 24 grit disc on the grinder more often than not.....Then I apply the filler.
I never use PREP SOL or even metal etch produstc under plastic.....just me- I am stubborn......
BTW-I [as many of you do]regularly see my work -later,that I have done-anywhere from just a few years, to as long as 25 years later....[by either knowing the person well] or seeing it at a show etc.....
I have never had filler release from the metal prepared this way.
My question is this: what is [or can be]wrong with applying filler this way when it can and does last may years? [I feel 25 years is a long time ].......
I respect OVERSPRAY's knowledge -so do not get the inpression I am saying otherwise....
Heres my Rant-
I hate to suggest this in the company of many experts -BUT.....I personally feel that the companies that sell our shops the latest variety of paint supplies are guilty of being skilled marketeers.
I cannot see the advantages of 5 products as opposed to three-get my point?

If you have ever tried to strip the paint off some of the '30's GM and Ford cars you can relate to what I am suggesting.

That old red primer that they used ,is stuck to that metal -almost STAINED or etched into it ,so good that it is impervious to strippers and will hardly even surrender to any type of sanding, either!!

NOW-consider this...that primer of which I speak is what ALL paint companies have ceased to make nor would even consider it a viable product to be used at all!

IT ....was an Alkallyd product,the lowest form of crap -implement finishes-TODAY- which Im sure contained gun powder and OR leads -[sure hazards were at play here]....
But you can hardly say that a product that has remained on a surface [with that much integrity], remaining after 65 years of life-is not -ANY GOOD-can you??!!!

 

Ok, So as I understand, all my wonderfull bondo job has to be ground off for concerns of rust forming on the steel under the filler. I can live with that.

Now, this is one of those quicky deals. Once it is all nice and smooth and purdy, its getting a spray bomb primmer job, a quick 400 grit sanding and a finish coat of spray bomb color.

Two questions come to mind right away.
1) Once I think the bondo job is done and I spray bomb it in primmer, I will discover I somehow missed a crater the size of a small planet. Do I have to grind off the primer at the "defect" or can I just put a little more filler there and re-sand and prime?

2) Since the "finish" coat will be a Paint by Spray Bomb color, will all the filler and stuff be "sealed" against the weather, or am I just pretending to be getting something done? Reason I ask, is because I have spray bombed stuff before (two or three coats) that had visable rust under the "paint" a year or two later. I always figured I screwed up the "paint" job, but maybe the product choice was the problem, not opperator error?

Thanks for the imput. This is one of the few places you can "ask the experts" where they ain't trying to sell you something. Gene

 

Choprods you have quoted the "gospel". You are exactly on the money.

That 30+ year old finish and primer is on top of heavily phosphated (treated) steel with a high content of lead and or chromate. That equals top quality corrosion protection which really can't be duplicated with todays automotive refinish products, and only some industrial coatings (bridge and water tower paint) would be close.

The tried and true test of the longevety of the work you have out there is proof that you have acquired the information and skills to make those products perform the way they are supposed to. Your observations and comments and the quality of your work are exactly the point I am after with all the technical crap I've been typing. (My 2 fingers are sore).

thanks
overspray

 

sounds like you're doing a quicky low buck low labor job on it, so you probably ought to just leave the bondo that's alread on, and finish as you are doing now. You probably want to sand the low spots down to bondo before you put more on, as rattle can primer won't do much for letting the next coat of filler stick.

Rattle can primer is not water resistant, but rattle can topcoat is (to some extent) although you probably don't want to go to the expense of putting gloss on it then primer.....which would do a passable job of sealing out the moisture.

If you were putting a "real" paint job on it, spending $100s on paint, then you'd want to do things correct from the beginning. I get the feeling you aren't in that boat right now for whatever reason.

 

Gene-the spray can primer and paint don't have the resistance to moisture because of the lesser amount of solids. Spray cans even at 2 to 3 coats of paint will only leave a film thickness of about 1 to 1 1/2 mills ( a dime is 10 mills). The resins in spray can paint are not very durable so for rust inhibiting they won't last long term. Knock off the spray can primer if you find a low spot to refill on your bondo. If you need to learn quickie used car fix 'em up tricks, I'm sure we could start another thread and bring up steel wool, plaster of paris, and a whole bunch of slipshod ways to fix cars.

overspray

 

I have actually welded patch pannels in this project and the seems have been ground and are pretty close, the filler is probably only 2 or 3 skim coats thick, maybe 1/8" thick max, its 2-3 skim coats cause I don't know what I'm doing with filler very well yet. The closest thing to real paint I've ever used is the tractor enamel at the local farm store. I'd use that here too, except it has to sit out side right now (got down to 39 last night) and the tractor paint (oil base) takes so long to dry. Some day I'd actually like to try real automotive paint...

Would the flat black paint (not primer) spray bomb seal as well as any other color spray bomb does? Would the "rustolem" bomb better then the "dollar general" bomb that is 1/2 the price?
I've seen a bunch of the quick car lot fixes, one of my favorites was the cement quarter pannels covered with bondo and painted. Rock solid, and worked well in the snow. The expanding foam thing has been done around here a lot lately, must be a "new" shop in the area? Gene

 

Thin the tractor paint with a little (10%) acetone, it'll dry faster. White paints usually have denser pigments (titanium dioxide).

overspray

 

screw spraybomb jobs. i don't know the reasoning behind you do it but you can spray a car with real paint for pennies more. i'm sure the opinions will rip all over here but if you want to do a GOOD cheap spray on a car the Nason line of paints is fucking awesome. really reasonably priced. you probably wouldn't be out much more for that route than a spraybomb job. hell Nason Select Clear is just about my favorite clear to use PERIOD. i've sprayed it over HOK bases a bunch with only good results.

the worst part of a spraybomb job other than it looks like complete shit 9 times outta 10 is wait til you try getting that shit off if you ever want to do a real paint job. 2 choices Aircraft stripper or ALOT of sanding disc. and when i say ALOT i mean ALOT. i refuse to try and work with it since a bad run of it several years ago. i'll just strip it and do all the bodywork its easier.

hell i'd say take it for a cheapy maaco job instead of spray bomb. probably about the same price and if you do all the prep work well(no spraybomb primer either)and take in just to be shot it'll look way better than any spraybomb job i've ever seen. don't cheap out on it if you've put this much effort in it at least give it real paint. i do custom paint but i also do jobs for guys that i know can't throw 5-10k on a paint job. i've sent out some pretty damned nice $500-600 paint jobs to. you don't get anything fancy for that price but it WILL be better than a spraybomb job. i used to have a deal with the local dupont rep when i was in autobody school(88-91) that got got dupont Imron really cheap. like $50-75 a gallon. that shit was hard as nails layed on good and held up great(used mainly on big rigs at the time). i could bring a car in shoot a few coats of high build on it wet sand the shit out of it spray it and send it down the road in a week and for the low price above or less and i kept over half the money after material cost. so basiclly i'm saying it can be done cheap and decent you just gotta do your research is all. they changed the formula for Imron years ago and it's a totally different animal now RIP...ken....

 

Hopefully this isn't a hijack, but I have the same kind of problem here only worse.

So, uh, yeah. The 50 Fleetline I have came with a shitty body redo (if you look inside the miss-shaped rear wheel openings, you can see the original ones underneath, bent back a little). One side has what appears to be the rear quarter patched from pieces out of a sedan, with about a 3 inch gap where the sedan door seam would be, filled with a mix of lead and some kind of bondo and the top tacked on with screws and was hidden under the trim. There is bondo front to back, that has been left bare for a long time. It looks like cheap stuff, too, lots of scratches and chips in it, but what do I know. I'm not sure much of the car's history before the last guy and all he did was bring it home.

It appears they also put the fenders/grille and left door from a '49 on it, although why the fenders who knows as they both rotted a little around the headlights and up by the cowl and have crappy patchwork there too. There's filler down low on both of them, leading me to wonder what exactly is under that as well.

Now, the one fender I am definately replacing, infinitely easier than hammering out the dent in it (same on the hood, it has a lot of light dents in it I'd probably have to shrink out), and I may replace the other side too depending what I come up with. Eventually I need to redo the one quarter entirely and the lower side of the other one, so that solves 90% of the rot issues.

That leaves me with one door that has a bunch of filler in the bottom. This car's sat outside at least two or three years now and when I got it a lot of the filler was exposed. All I've done was rattle-can the sides so it was mostly one color to make it look a little more presentable for the clowns who live nearby.

If I grind it out and start redoing it one panel at a time, what do I want to do - have some good primer put in a spray can so I can cover bare metal and use some kind of color to seal as I go from panel to panel, then come back and sand it all when time comes to have it painted? I have a lot of work to do, and it will be a long time before it's painted. So I need to be able to seal up an area when I am done with it to prevent the same problems from happening all over again.

I am planning to put this in a garage over the winter. I don't have a compressor and I pretty much have to do all the work outside while I have it here at home. Eventually I have a guy who will paint it pretty cheap (I supply paint), it will be like a Maaco job but that's good enough to enjoy the car.

Thought maybe this would be good to know for other folks, too -