Painting Fail!

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Painting Fail!

Postby starfire » Sat May 02, 2015 8:24 pm

OK, I've had the rear bumper cover off of my Firenza for a long time now. I stripped all the old paint off, then washed it well, then used Duplicolor Plastic Prep spray on it. I then used the Duplicolor Self-etching primer according to directions (says right on the can it can be used for plastics). It looked good so I then the next day I shot it with the Duplicolor Universal Black, 3 light coats. 10 hours later I checked on it and found the paint had bubbled and I was able to knock off this much with the side of a piece of sandpaper. It looks like the primer did not stick at all:

Image

Any ideas on what went wrong and how (once I get all this scraped off) I can successfully paint this bumper cover?

Thanks,
Alan

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1987 Oldsmobile 442

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Re: Painting Fail!

Postby cjbiagi » Sat May 02, 2015 9:18 pm

You said you washed it, what did you use? Also, did you scuff the paint before applying the primer? It looks like either something was still on there or you need to sand the paint to roughen it up a bit.
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Re: Painting Fail!

Postby starfire » Sat May 02, 2015 9:31 pm

I washed it with palmolive dish soap and warm water, then rinsed thoroughly with cold water. There was no black paint left on the cover. I took it down to bare plastic on the black, the red did not strip off like the black did and I scuffed the red up with 1200 grit sandpaper. I haven't checked the primer on the red part to see if it stuck completely. I'd say there was an issue between the primer and the black, but they are both from the same manufacturer.
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1987 Oldsmobile 442

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Re: Painting Fail!

Postby starfire » Sat May 02, 2015 9:35 pm

I just checked over the red area and the primer seems to have stuck fine to that. It's just in the lower black area. I guess I'll just sand all the black area down with 320, clean, respray with primer, respray with color and see what happens. I'm just so tired of not having this part on my car. It's just been this past week it's been warm enough to paint.
Alan

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1978 Oldsmobile Starfire Firenza
1987 Oldsmobile 442

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Re: Painting Fail!

Postby cjbiagi » Sat May 02, 2015 9:59 pm

I like to wipe the parts down with a solvent based cleaner, like wax and grease remover. Some soap may leave a residue even after rinsing, not sure about Palmolive. I always have a gallon of wax and grease remover on hand but auto parts stores sell smaller cans.....just a thought. Also, you always want to clean the part with solvent before sanding, otherwise you can sand whatever is on there into the paint.
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Re: Painting Fail!

Postby 67shovel » Sun May 03, 2015 10:42 am

Didn't know what your problem was till I read where you scuffed it with 1200. 1200 is to fine of grit. 400 is more like it IMHO.
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Re: Painting Fail!

Postby starfire » Sun May 03, 2015 10:56 am

67shovel, it stuck to where I scuffed it with 1200. I didn't scuff the area that used to be black because it was down to the bare plastic. I sort of assumed the self-etching primer would not need scuffing done on bare plastic. I guess I need to look up the definition of "self-etching" :D

Clyde, the Duplicolor plastic prep is a degreaser/dewaxer.
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Re: Painting Fail!

Postby spencerforhire » Mon May 04, 2015 8:49 am

I do believe self-etching primer is meant for bare metal. Plastic and urethane can be a real pain to get anything to stick, especially if it's ever been exposed to any kind of silicone spray or Armor-All. Sometimes it takes something stronger than the usual "paint-prep" to get the surface clean and dry. I like lacquer thinner or acetone; they will often dull the surface, which is not a bad thing when you're trying to get paint to stick.
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Re: Painting Fail!

Postby starfire » Tue May 05, 2015 7:30 am

Well, I used "Goof-Off" which I believe is acetone based to take off the black paint. Oddly, it appears the factory just sprayed black color on the cover (unless they used a black primer) as I did not get any color other than black when I stripped it off. So the final wipedown was made with Goof Off, followed by soap and water wash, followed by plastic prep, followed by Self Etching primer (which says right on the can that it can be used on plastic). The primer didn't bubble until after the 3 light coats of black were put on. The primer had cured for 24 hours. Maybe I should just sand everything with 320 grit and try spraying the black again without primer.
Alan

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1987 Oldsmobile 442

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Re: Painting Fail!

Postby HI WINDING MONZA » Thu Jul 02, 2015 7:30 pm

You need Adhesion Promotor, sold by Duplicolor or Rustoleum in a spray can. Wipe the surface after cleaning with rubbing alcohol , you have a 10 minute window after the promoter for the top coat to be applied.

Just did the J's rear bumper with it 2 weeks ago, ( was all red before)
DSCN1903.JPG
BEFORE
DSCN1903.JPG (74.67 KiB) Viewed 226 times
DSCN2033.JPG
AFTER
DSCN2033.JPG (74.37 KiB) Viewed 226 times


On My Monza in my Avatar, I just used black spray can primer , then PPG Delstar Enamal with a flex additive added. Just started to crack (paint )after 20 years years of service when I sold it.

They do sell bumper paint in the spray can in Flat , Semi and Gloss now ..............

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Re: Painting Fail!

Postby cjbiagi » Thu Jul 02, 2015 7:46 pm

The bumper paint works great and gives a very nice finish. It sounds like possibly the two paints you used had some sort of compatibility issue. Were they the same brand and designed to be used together?
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