The Stovebolt Site Forums The Shop Area Paint and Body Shop (1) Filler and (1) Spray Can Paint Question

Question One:
Some parts I have just had sandblasted have some corrosion that was hidden prior to the blasting. I am assuming that the thing to do is to go to the FLAPS and pick up some Bondo.

But it has been many decades since I did anything with metal filler, and perhaps there is some basic information I should have before I start the process.

Prime first?

What brand or sort of filler should I use?

I have attached a few photos of the corrosion issues I need to deal with.

Question Two:
I was painting my firewall and came up with an issue I didn’t expect. I had put on a couple of coats of gloss black and didn’t like the fact that I could see the spray can passes if I looked at the result in the right light. So I got one of the Rustoleum high output cans to add a coat with a broader spray pattern.

It had been about 3 days since I had painted the previous coats, so the suggested drying time had passed. I thought the coat from the high output Rustoleum can looked good…but when it dried, there were patches where the paint had shriveled up (like an exaggerated wrinkle finish).

Between the coats with the standard spray can and the last coat with the high output unit, I wiped the surface down with a tack cloth.

I had mis-remembered the brand of the standard spray can paint. I thought that it had been Rustoleum, the same as the high output can that was used for the last coat…but it turned out that the first coats had been Ace Hardware brand paint. Would you think that using different brands of paint was what caused the “wrinkled” patches? Other possibilities?

I have attached a couple of photos that show the wrinkled effect that showed up.

Thanks for your thoughts!

Nick, the answer to question 1 is to first use an encapsulating sealer like Master Series Silver or Eastwood Sealer. This will stop any remaining rust from getting worse. I wouldn't use the Bondo Brand plastic filler. I would use a better brand. I don't have one to recommend but Eastwood sells it. Once you have used the filler and have it where you want, seal it again to keep moisture away from it.

Question 2 is yes, the 2 different brands have reacted to each other and caused the issue.

To fill rust pits, and especially the pinholes, the body shop I once managed used Devcon Epoxy Steel. I think the name has changed since then, but the product Devcon sells these days is essentially the same. It's basically atomized steel powder in an epoxy carrier that's MUCH more durable than J-B Weld.
Jerry

Wrinkle is two types of paint if I remember correct one will be a thinner with lacquer and another with mineral spirits .

Thanks all!

I have ordered Eastwood paint and filler and just ordered the Devcon product that seems to be what Jerry was suggesting...Devcon Metal Patch and Fill 50345.

I will make a point in the future to stick with one brand of paint! I certainly didn't intend to create my own Wrinkle finish mixture!

I've had a few issues with painting with Rustoleum semi-gloss black from a rattle can if I didn't wait even longer than the recommended 48 hour recoat window. I'd sand the wrinkles off and repaint after 2 full days and the dang wrinkles would come back. It could be even worse mixing paint brands. Shooting a lacquer based paint over enamel is a guarantee of wrinkling the previous coat.

It has been about 7 days since I ran into the issue with the wrinkling of the Rust-Oleum gloss black over the Ace brand gloss black. (It turns out that both are enamel paints.)

I sanded down the wrinkled areas and repainted the firewall. This time the paint didn't have any issues going over the previous layers. I believe it is the same issue that Kevin (klhansen) mentioned of not believing the suggestion of waiting 48 hours before recoating - give it more time.

Thanks for the input!

My personal opinion is that right from the beginning of a project consider biting the bullet and ditch rattle can paint as much as possible.
With the amount of items that need primer and paint the spending for a paint gun (or 2) and different cup sizes will seem like nothing after how many rattle cans you burn thru.
If you shoot your primers and finishes on non critical parts and areas early in the build you will work thru all the nuances of your equipment and paint systems while developing your confidence/skill for when you get to critical areas, where it really matters ….
You will also figure out how to clean your eqpt with an efficient sequence of wipes and cleaners etc to reduce your solvent waste.

Most importantly you will achieve a quality unobtainable from a spray can…

Chuck

Chuck,

It has occurred to me that I should consider that route.
I don't expect to shoot any high quality finishes, as outside, or the family garage are my only options for spraying...and the winter where I live rules out painting outdoors.

Most standard recommended recoat times are calculated based on an ambient temperature of 70° F. If the temperature of the substrate or the environment is lower than 70° F, you must allow for significantly additional cure time between coats. Applying the next coat too early in cool conditions will impede solvent evaporation and potentially compromise the final finish.

In addition to overall cure time, the flash time between coats plays a crucial role in preventing adhesion issues and surface defects, such as wrinkling. Flash time provides the necessary window for initial solvent evaporation, preparing the underlying surface for the next layer.

The application technique should be as follows:

• First Coat: The initial layer should always be applied lightly and must be allowed to flash properly. This lightly flashed coat acts like the sticky adhesive on tape, creating the ideal surface profile for the next layer to bond reliably.
• Second & third Coats: Once the first coat has flashed, the second coat can be applied at a medium to heavy thickness. Note that the required flash time before applying the third coat may even be longer than the flash time allowed for the initial coat.

If you do not allow the paint between coats to flash properly before applying the subsequent layer, the paint will not have enough time to evaporate all the solvents. When the topcoat is applied over this trapped solvent layer, it can prevent proper cross-linking and bonding. This solvent entrapment may cause the surface to wrinkle or lift as the entire coating system attempts to cure completely.

Phil,

I believe that you are spot-on. My garage is not very warm and the nights were cooling down when I painted the firewall. I'm sure now, that my problem was caused (as you suggested) by not waiting long enough. Patience is something I need to work on!

Thanks!

Phil, novice with car painting with only a couple under my belt helping. You keep referring to proper flash time and I know that has to do with experience, but what are tell tale signs to watch for?

I usually touch a masked area looking for slight tackiness at a minimum. Waiting until it’s just dry to the touch is even better.

Usually the can will give you the recoat time, but as you found out, it’s temperature dependent.