heat gun for painting / caulking in cold?

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Old 01-03-16, 08:32 PM
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heat gun for painting / caulking in cold?

I need to scrap and sand under my truck and then spray rust reformer followed up by rubberized undercoating, before we get salt on the roads once it starts snowing.

The cans say it should be at least 50 degree Fahrenheit, but it will be about 44 day high and then go down to I think the 30s. I can't wait to do this until spring. I can't really fit my truck in my garage and run a heater in there while it dries. Most caulks are more ok to use in cold weather but am wondering about using a heat gun on them also to speed up the curing/drying.

When I paint under the truck, do you think I should run the heat gun over everything while the rust reformer is freshly sprayed? Something about having it cure/dry quickly like that makes me think it might not be as strong as a slow-cure but I'm not sure.
 
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Old 01-04-16, 02:46 AM
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A heat gun will not help you.
The temperature of the truck will determine how the coating cures. Blowing a small amount of warm air at a cold surface will not do very little to help cure the coating.

Since the truck already has some rusting it might be better to wait until next summer where you stand a chance of your treatment working or work at cleaning out the garage.
 
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Old 01-04-16, 04:20 AM
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I agree! Coatings are dependent on both the substrate and air temperature to dry/cure properly. It might be possible to rig up some kind of 'tent' and then heat inside it to bring it to the proper temp.

The only way a heat gun might work is if you were only covering a few sq inches ..... and then you'd need to continue with the heat until the coating dries
 
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Old 01-05-16, 03:04 PM
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I might just wait until spring or if we happen to get a few days mid winter that are over 50 and not such low overnight temps. What's one more winter of salt (from snow) that is the major cause of this? The truck is a 2000. I'll have two days in a row of 45 degrees during the day but it's supposed to rain. Maybe I'll put a tarp over the whole truck while it's drying but I know humidity is a factor also.



When metal's cold, it gets that moist kind of feel, you are right I think, I asked two forums and both said the surface temp is the major factor.



Someone mentioned if it will even help at all, that they had all types of sprays in the 1970's that didn't work so well. I'm sure the ingredients got better, but possibly worse in a way because they might have omitted VOCs from the modern ones thus making it weaker. The metal is flaking off from rust. I feel like some areas I can just keep chipping away at it and have almost no metal left. Some parts were sprayed last year (but without sanding first) and they are crumbling off already.



I doubt it will get so bad that the truck basically collapses on itself but it is pretty bad, the floor board even has a 6"x6" hole covered by the rubber floor mat. I wonder what the hell Ford was thinking making a vehicle out of this kind of metal, I know that better metals are used in other cars and some from the early 80's are practically rust free. Two of the wheel hubs have 3"X8" holes in them and should be replaced but I'm not going to cut out and weld in a new wheel hub from a junk yard. I just fill with bondo and spray paint it. My main concerns are things just getting worse and the body looking ridiculous with holes in it but has none really now. And then underneath, the strength being compromised, things like fuel filler neck has a hole in it and leaks gas when filling. I'm worried rust particles will get in the gas tank and ruin the fuel system. There are lines in metal pipes I'm surprised are still there. Also, there's a slight chance I might get a trailer for this truck and I don't want to risk bolting it up to a weak frame, although I know a lot of rust trucks haul trailer and saw a complete rust box van with holes all in it and everything and they had one of those telephone pole cherry picker cranes built into it.

I got such a good deal on the truck, I knew it had rust but not this bad, I looked under and still bought it. I should have done this over spring but I some how used up like 10 cans of the rust reformer on small machines and winter crept up. I just bought about $200 more of the rust reformer and the follow up rubberized coating.

I bet it would work ok if temps and humidity are not the optimal conditions the can says, because rustoleum wants to keep themselves way in the clear of giving bad advice and thus having warranty claims and such but I'm not sure if I'll wait until spring or maybe do it with a tarp when it's supposed to be around 44 as the high two days in a row and as estimated 1/2" rain one day and 1/4" the next. Or wait for a warm front in winter and hose off all the salt underneath and get car washes as much as possible after snow storms (salt).
 
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Old 01-06-16, 03:09 AM
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It sounds like you really believe the "rust reformer" claims on the side of the spray cans.
Yes, there is chemistry available that will convert rust to an inert piece of residue but the larger the rust particles the less likely it will last.
I have used these treatments with limited success but only after mechanically removing most of the rust with a wire wheel, grinder and sandpaper.

If you go at it and make it look like there is nearly no rust before you put on any rust treatment it may last a little while.
 
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