Paint woes!

[Guest]

I've been painting bikes for the last 7 years and have developed my own"system" for quick colour changes. I pull the "tins" from the frame (duh), repair scratches and other surface problems, wet sand with 400 and 600 grit, rattle can primer surfacer (if down to metal or covering filler), rattle can colour coat, wet sand with 1000 grit and shoot a coat of urethane 2 part automotive clear.

I've had my ups and downs over the years, all part of the learning curve, but was now at the point where I felt confident to tackle 2 jobs this weekend. With 3 or 4 days ahead of me I figured I could get them done with a minimum of fuss. Wrong. I'm still on the first project, a red bike becoming black. Prepping the "tins" was no sweat as everything was in good shape. Just some sanding to remove decals and 600 wet to give the next paint some tooth. Wipe down with mineral spirits and "air dry" in the sun.

Shot the black paint ( Rustoleum Multi surface) and the fun begins. Everything fine with tank, side panels and fairing but the tail.....instant orange peel.. Let it dry, sand it all off and start again. Comes out better this time.

Let it dry over night and then wet sand with 1000. Get out the new HVLP gun and run some cleaner throught it. All set for clear. Shoot the tail piece first and almost immediately problems. Looks like little "craters" maybe 1mil in diameter. Its not all over just on one side. Crappola!

Let it dry and sand it out but now I'm into the previous coat to get these craters out. wipe clean and air dry. Paint with colour and bang....problems again. Now its "lizard skin", but again only in patches. Grrrrrrrrrrrrrr!

I'm not sure whats going on other than contamination of some kind. With the "craters" I think I might not have fully cleared the gun before adding the paint. The others can only be the mineral spirits not"flashing" off. I'm very aware of contamination and always wear latex gloves when handling parts, I wipe off everything after sanding with lint free towels and mineral spirits but i guess the lesson is you can't be too careful with the prep.

At this point, I'm still working the base coat and haven't attempted the clear again. I think I might be a bit "gun shy" about that.

Anyway back to it. I'll likely get the other one done next weekend now.

I'll let you know how it all turns out.

Cheers,
Spyug

[Nessism]

Did you degrease the surface before you sanded the old finish? Wondering if some contamination might have gotten ground into the substrate while sanding?

[Griffin]

Sounds like silicone contamination on the surface. Many lubricants and spray metal protectants have silicone in them. ANY trace of silicone will bubble the paint and it will peel off the surface as soon as it dries. I've experienced it first hand, and have worked with several factories that have painting or powdercoating processes to remove any traces of silicon from their compressed air systems.

You probably need to sand down to the plastic, and then thoroughly clean the plastic with mineral spirits and denatured alcohol.

[TheCafeKid]

Ive had this problem with "Rustoleum" products. They recently came out with a line of high temp motor paints. I tried em, they seemed to lay down better than the Duplicolour stuff, at first, so i thought maybe i'd found a new paint. Let it tack, then shot the next coat. Craters, crackles, wrinkles etc.. The stuff would not lay down. i stripped it all off and went back to my Duplicolour and never used anything else..BTW, I seem to recall someone saying that Rustoleum had the same vase as Krylon, dunno if thats true, but that would explain A lot, as krylon you have to strip EVERYTHING OFF, or it will freak out when you lay it down..

[Macguyver]

You probably need to sand down to the plastic, and then thoroughly clean the plastic with mineral spirits and denatured alcohol.

You got 'er Griffin!

It might not just be silicone though, it could be almost anything people use on their bikes, or any cross-contamination in the cleaners.
I have also seem this exact problem with parts painted with old urethane paint reacting with the new paint, even though it was painted 20 or 30 years ago!

I would sand it right down to bare plastic front and back, wipe down with laquer thinner and start again. I know it's a PITA, but you can't bury contamination or reactions.

It sounds like the reaction is lessening with each sanding and repaint, so you are getting the bad stuff off of the part so it is not likely to be cleaner contamination, but I would check your solvents anyway and make sure no one has used a greasy rag on the filler neck. (by mistake of course)

A complete gun cleaning wouldn't be a bad idea either, not really related to this issue, but it's always a good idea.

Best of luck.

[TitanNeil]

Any chance of compressor oil in the line? You have a good filter and dryer, most likely. I just base/cleared some bike bodywork for the first time a few weeks ago and had this problem on one piece. When I shot the clear it came out with 1-3mm 'craters' as well, looked like a drop of water stuck in the gun came out in bits, just on one pass. I was using a small portable compressor and cheapo inline filter so I think it was condensation that had built up and came out at the end just as I was finishing the job.
I have other parts to paint so i'll sand down this piece and reclear it at that time.
As an experiment, I took some clear nail polish and put daubs of it in the 'craters' to fill up the spaces. I'm curious as to how well it will work as a 'filler' for clearcoat. I'll report back...