Spray paint blistering WHY

[auctioneeral]

Ok men, Need some help here. Everything was going good as seen i other post on spray painting my plastic parts. Here is the other post link. viewtopic.php?f=7&t=9389

Side covers turn out good i think and i have not changed anything on the way i did the side covers.
But my front fairing is kicking my a-- on not going right. Top coat blisters up in different area's. I took yesterday wet sanded the blister spots away, sprayed primer this morning on it and looked good. 15 minutes later sprayed top coat and it blister in different areas again. I even tried warming top paint can up in hot water still. I didn't warm any cans up on the side covers.
Side covers got sanded primed sanded and top coat. One was done primer and top coat same day the other side cover sat 4-7 days before top coating without any problem.

I just when and got my lid for trunk out of shed which was cold and sanded primed and top coated it all within 1 hour with out problem.

Paint using is
rust-oleum 2x ultra cover gray primer
rust-oleum metallic brilliant metal finish #7251 cobalt blue metallic

 

[dan filipi]

My first thought is it wasn't clean.

 

[auctioneeral]

I wet sanded the primer in tub and though i washed it off good with it in there. But thats just me thinking again. I'm going to give it another bath and sanding and see what happens later.

 

[dan filipi]

I'm no painting pro so wait for some other replies.

 

[joedrum]

id say its something the abs in trunk has absorb ...ive never done any painting on plastic ....but in wood finishes silicone can be real problem ......many furniture polishes is full of this stuff ... sheesh cant remember what the product name was that help this ...maybe it was old fish eye....it really was a silicone homogenize product that was mix in the finish...just guessing here but the way it didnt bother you on side covers ..kind of leads me here on this....not much help i know on rattle can paint

 

[Ansimp]

+1 on silicon or oil contaminant. I alway try to use Prepsol etc before painting.

 

[zman]

RightyO..Looks like oil or silicone contamination. when the paint is oxidized and wax is applied the wax will go deep into the paint so it takes allot of sanding to remove it. I have never used spray paint for for body work but on metal parts like engine blocks I use WD40 to fix area`s that do that, things recessed areas that are tough to sand or remove contaminates from.
What I do is sand best I can then spray liberally with WD then wipe down with a lint free cloth leaving a haze of WD, cheese cloth is best for wipe down but not the sticky cloth, the regular untreated cloth. The paint seems to flow better and adheres to the surface very well. Cant wait long before painting cause the WD will attract dust.
Joe is right about the fisheye stuff, we used that in the paint mix as a preventative...not sure it can be wiped on and is expensive stuff for a little bottle, maybe cheaper as used in woodworking isle.

 

[AApple]

zman » Sat Mar 07, 2015 10:04 am[/url]":34ar6je3]
What I do is sand best I can then spray liberally with WD then wipe down with a lint free cloth leaving a haze of WD

Whuuuut? :headscratch: Spray paint on top of WD40?? Seems like that is counter-productive...paint on oil. Never(intentionally) done that, but it's something to ponder upon.... :read:

 

[dan filipi]

AApple » 11 minutes ago[/url]":22yi989p]

zman » Sat Mar 07, 2015 10:04 am[/url]":22yi989p]
What I do is sand best I can then spray liberally with WD then wipe down with a lint free cloth leaving a haze of WD

Whuuuut? :headscratch: Spray paint on top of WD40?? Seems like that is counter-productive...paint on oil. Never(intentionally) done that, but it's something to ponder upon.... :read:

My thoughts exactly.
Woulda never thunk it.

 

[slabghost]

Ansimp is right on using solvent to wipe off waxes and silicone. Personally I prefer to do that part first before sanding. That prevents the sand paper from being contaminated with oils silicone or wax residue. Contaminated sandpaper will have you pulling your hair out.

 

[zman]

Give it a go on your next project. Been doing it for decades with no problems. Things like engine side cover in gloss black came out like a powder coat, also used to prep the GL engine under the carbs where the gas had leaked/gummed up all over into the creavases, has never failed and always held strong where I have used it.

 

[joedrum]

i dont think theres oil in wd 40 ...it is alcohol and gleserin based and will make metal rust once evaporated so i bet z-man is on to something

hmmm heck its on the can dont go by my memory ..but rust is a for sure thing ... so cant be real oil in it

 

[slabghost]

The solvents in the paint can get by some oil without issue. Some paints have oils added to them for special purposes. WD40 will evaporate off if given some time.

 

[Dadster]

Allen I ran into the same problem on 1 saddle bag lid. I sanded out the blistering, primered the area applied the new color coat and it blistered along the edge of the new primer. I resanded and primered the whole lid again and will let you know tomorrow how I made out.

Maybe a couple extra coats of primer would seal the surface better and stop this. Just thinking out loud.

Bill

 

[auctioneeral]

Bill Let me know how you make out. I just sanded all the blistering out of it.

 

[Dadster]

Will do

 

[mike in idaho]

dan filipi » Sat Mar 07, 2015 6:32 am[/url]":1n2rl9h6]
My first thought is it wasn't clean.

Stop wet sanding it, the moisture it the substrate surface is causing the problem. Let it dry a couple of days, then wipe it down with proper wax/grease remover(no WD40).

 

[auctioneeral]

Ok Mike thanks

 

[slabghost]

mike in idaho » Sun Mar 08, 2015 10:18 am[/url]":357ea32t]

dan filipi » Sat Mar 07, 2015 6:32 am[/url]":357ea32t]
My first thought is it wasn't clean.

Stop wet sanding it, the moisture it the substrate surface is causing the problem. Let it dry a couple of days, then wipe it down with proper wax/grease remover(no WD40).

While the substrate may hold moisture for a bit. Primer is porous. It will dry pretty quick unless it's very humid. Wiping with solvent before painting is always a good idea to remove any hand oil or wax missed previously. I've always dry sanded primer and used a tack cloth just before the color is applied. Wet sanding is best as a first step to be sure the surface is scuffed so the new paint will stick. Then again at the last if you really want the glass smooth finish. :thanks:

 

[joedrum]

im incline to try wd40 ... and will ... the poster use same method on side covers...im incline to believe his method has work and inclined to believe its a contamination deal in the trunk itself

so im going to try wd40 on something ...ive done lots of wood finishing and can make mirror finishes in wood ...all done in ways not really proper by industry products ... easy to test things ..on scrap stuff ....