I try and use epoxy as much as possible, but sometimes on small collision jobs, there is not enough time to spray epoxy, wait 24 hrs., then apply filler. In that case, I apply epoxy over the metal and filler before 2K. My question is the time needed between epoxy and 2K. I am sure the times vary depending on temperature and the application of the epoxy, but what is safe? Sometimes it works out that a repaired area is ready for primer before I go home, and I will put 1 unreduced coat of epoxy on, then spray 2K the next morning. Ideally, I like to let 2K sit overnight, but I don't like rushing the 2K over epoxy, either. I have used a light to medium coat, reduced 25% or so, over metal spots and then shot 2K an hour later, but I'm not sure if it is good practice. I did have epoxy edges "lift" once. The repaired area was epoxied, then 2k an hour later. The repair sat outside for 3-4 days while I waited on parts. When sanded, the 2K edge ended up inside the epoxy edge, and when base coat was applied the epoxy edges "lifted", for lack of a better word. SInce then, I have kept the epoxy covered with only a 2K edge showing, and it hasn't happened again.
Epoxy and collision work
- Thread starter texasking
- Start date
serjik911
Promoted Users
i would use it as a sealer, but tech sheet says to let it seat for 2 hours before paint and i have only 10-15 mins for sealer coat. i wonder if i can use spi sealer. the tds says "from 10 mins to 2 hrs" but thats kinda too big range to be sure that it will be dry after 7 mins of air dry and 3 mins of bake flash.
Jim C
Oldtimer
it all comes down to how thick the coat of epoxy is. if you keep it to one super thin reduced coat then you can put 2k over it quick. 15-30min maybe. if you put a single or multiple unreduced coats on that you sprayed and made it look good then most likely thats too heavy to put 2k over until the next day. remember epoxy is very slow so if its thick then your putting on a fast flashing and curing product over it. you will have a hard crust over a gummy base. remember the epoxy if not somewhat cured is going to soak up the solvents from the 2k rewetting it and making it soft again. when the 2k dries it will shrink. since its on a gummy base then as it shrinks it can creates small cracks in the 2k or you may see it pulling at the edges of the panel. this is all ok once its cured but youll need to sand out all those defects. a thin coat that you can see right through is what you want if your looking for speed. epoxy at 1:1:1 for quick stuff.
The problem with SPI sealer is it is a urethane and as with any urethane not the best over bare metal. All of the majors say it is ok to spray urethane over small metal spots, but I have never understood how the urethane knows how big the metal spot is. It either likes the metal or it doesn't.
AAE
Learner
A very light dusting of epoxy over bare will take care of that issue.
jlcustomz
evil painter
I'd agree with both only a light reduced single coat & hit it with an infared lamp after initial flashing. Even a light barely covering coat of epoxy on a spot in collision work is better than most will do & will give you peace of mind. It's as much the uv rays as the heat that speed things up.
Even a single 250 watt screw in heatbulb for 8 bucks in a sturdy adjustable lamp can do the job for a small spot. Check with IR gauge. 90 to110 degrees is safe right after spraying thin, up to approx 140 after dry to touch, about 160 to170 can risk bubbling entire area.
I occasionally like to squeeze in a few minutes with leftover product just for experiments while working on jobs. Best way to get a feel for how much to push things & when.
Last fall I dipped an unprepped spray gun wrench in epoxy & wiped to slightly thick with stick & set on hood of white van in mild sun & approx. 60 to 75 air temps. About 3 hrs in it felt hard but thumbnail would scrape it like cheap crap, 6 or7 hours later thumbnail couldn't touch it. IR gun never even hit over 90. Other sample in shade was still not nail print proof late afternoon, so that shows what infared rays will do for you.
Even a single 250 watt screw in heatbulb for 8 bucks in a sturdy adjustable lamp can do the job for a small spot. Check with IR gauge. 90 to110 degrees is safe right after spraying thin, up to approx 140 after dry to touch, about 160 to170 can risk bubbling entire area.
I occasionally like to squeeze in a few minutes with leftover product just for experiments while working on jobs. Best way to get a feel for how much to push things & when.
Last fall I dipped an unprepped spray gun wrench in epoxy & wiped to slightly thick with stick & set on hood of white van in mild sun & approx. 60 to 75 air temps. About 3 hrs in it felt hard but thumbnail would scrape it like cheap crap, 6 or7 hours later thumbnail couldn't touch it. IR gun never even hit over 90. Other sample in shade was still not nail print proof late afternoon, so that shows what infared rays will do for you.
Chris_Hamilton
Trying to be the best me, I can be
If you are in a hurry like that it's best to not use epoxy. Better off using urethane, trying to force epoxy to cure quickly is just setting yourself up for problems down the road. If your Bosses are rushing you that much they aren't worried about quality and how long a repair lasts anyways.
I know this personally as I had argued for better practices to improve quality at several shops that I've worked at. (that word gets thrown around a lot in collision repair, but very few Collision Shops really care about it in reality). In the end my Bosses viewed me as the problem not the piss poor work that was going out the door. Shop that is focused on volume, you are better off doing it the absolute quickest dirtiest way you can get away with. Most Collision Shop Owners equate speed with skill when in actuality that's not really the case. So urethane it and send it out the door, then get a raise from your Boss.
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Over reduced epoxy (1:1:1) will not cover much, and is basically an adhesion promoter. If I were still doing production collision repair for somebody else, I would just spray a urethane sealer over small sand throughs like 99% of shops are doing. The difference is I work for myself, and I know urethane does not like bare metal, and I try to do a better job than what 99% of the other shops are doing. Epoxy is a great product, but for high production work it is just too slow, and trying to rush it will bite you. Almost any sealer is going to want at least 10-15 minutes before base, so using epoxy 1:1:1 is an option if you can wait 30 minutes, but if not I would just use urethane.
Chris_Hamilton
Trying to be the best me, I can be
And again...lol. We gotta stop doing that Texas
crashtech
Combo Man & Mod
Lots of ground has been covered here and good info, too. I know that I've had close to 14 years of trying with varying degrees of success to use SPI epoxy in collision work. Along with all the special techniques, heat, time, late nights and weekends, lets not forget to educate our customers about the advantages of being given extra time to do the job. The idea that improved cycle times benefit repairers is a fiction invented by insurance companies to lower rental bills and discourage supplements. My customers, at least the ones who care for their vehicles, are very open to the idea that quality takes time. Once you take the time to educate them and get them on board with the idea that your shop uses processes that are superior but a bit slower, the rest becomes much easier.