I have an 85 and have pulled off the bumper cover. The paint is peeling off it and I'm looking for any suggestions for completely removing the paint.

I used 600 grit sandpaper, wet. DO NOT use any kind of stripper, it will melt the urethane. This includes fibreglass stripper.

my concern is with the flaking. I'm afraid of putting new paint over the old, even if it's sanded, and have it flake off again.

You'd sand it down to the bare material and then prime and paint it. And you'd use a flex additive when you paint.

Matthew

The paint shop I went to told me there's no need for flex additive anymore.

Is this B.S? Where do I get it from?

It is B.S. especially on the C4 bumpers, they are so prone to warpage. You can get the flex additive the same place you get your paint.

Paints today are much more forgiving than paints of yesteryear. Flex additive is primarily used to assist in the assembly process, it is not used to provide long term flexibility. I've painted about 6 C4's and several C3s, both with OE bumpers and fiberglass bumpers. I haven't used flex agent in years and have never had a problem.

True fiberglass stripper can damage flexible bumpers but, there are strippers designed exclusively for urethane and other flexible bumper materials. SEM makes a great product part number 77713. Bull Dog is another good line of products part number 9161 is an excellent product. Always try any product in an inconspicuous area but I've never seen either of these products damage a bumper. I have used them on C4 bumper covers. Some factory paints will prove too touch for them to soften and remove though.

If the old paint is not chipped, cracked or bubbling and it is the original factory paint it should provide a fine substrate for new paint. It's not generally necessary to strip the bumper all the way to bare urethane.

If you do decide to strip the cover I would suggest a finish DA with 220 grit paper. Doing it by hand will take you a long, long time if it's factory paint.

I've had '91 up C4 bumper covers stripped with media as well. Plastic beads or walnuts. I can't remember exactly what the guy used but all he does is media blasting and he's very knowledgeable with different medias. I had a particularly stubborn '91 front cover with several coats of paint. One hours labor charge and it was down to bare urethane. It was an interesting experiment as it was the first cover the blaster had ever tried but I was fairly convinced it would work. He tried different medias (he was curious as well) and nailed it.

While a lack of flex additive is generally the scapegoat for poor paint adhesion on flexible body parts it is the cleaning, prep and adhesive promoters used on these parts which causes adhesion problems. This is more critical on new covers as the mold release agents used can be very troublesome for top coat adhesion. If anyone is planning on painting their own covers I'm happy to cover that procedure as well.

Ok, I'll give it a shot as is. If the paint falls off I can always try again.

I was speaking from the experience of having my own car repainted, obviously VtVette has much more experience. I would do what he says. I was afraid to sand mine down with a da so I spent many days with a sanding block and 600 grit paper, now I see I could have saved myself a LOT of time. Thanks VtVette for the guidance.

I have the DA and 220 grit. I was afraid it would be too rough though and scratch the surface underneath and show through the paint.

Fuck it. I'll pull the bikes out of the garage this weekend and get started on the front. I'm sick of putting it off. I need to clean up the garage as well and maybe paint the bare sheetrock in there to keep the dust down.

If there's primer under the paint, stop when the 220 hits it and switch to 400 or 600.
I use my DA in one hand and the shopvac in the other.

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I should have elaborated on this - 220 to "cut", then 400 to 600 for finishing up. The only time I go to 600 is metallics or pearls. Also, check the P sheet for the specific paint system you are using. Some suggest no higher than 400 or 500 grit paper.

Once you've DA'ed with 220 if you have a lot of "bulls eyes", where you've passed through one coat of paint to another (or primer) you may find it easier to get the surface smooth by switching to a ridged block and hand sanding the bumper at that point.

I'm glad to see your reply VTVETTE because I was just on a web site looking at the SEM bumper stripper and wondering if it would work. I really wasn't looking forward doing this job with sandpaper.

VtVette please go over the process for stripping the paint from the bumper using one of the products you listed and repainting it. Also, can you give suggestions for body filler products and paint products for a vette.

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Well, I'll start, Brian can add to this.
First, what equipment do you have? A DA? Compressor & gun?
Sanding block?

If you're going to use a DA, it's very important that you keep it flat against the surface and stay away from the ridge and the edges of the tail lites, do those by hand. A DA can leave a gouge faster than you can imagine if tilted.
Use 220 with the DA and don't try to get everything off with it. Like Brian said, there will be a bunch of bullseyes left and those should be block sanded. Unless you've done boatloads of handsanding, you have to use a block so your fingers don't leave impressions.
Dura-Block is a good sanding block about $7 for a 5 1/2inch and $10 for an 11 inch. It can be used wet or dry. I prefer wet myself. An old Windex spray bottle is nice for wet sanding. Do the rest of the sanding with 400.

SEM makes good stuff and their high build primer is urethane
compatable. the high build is nice because it will help fill sand scratches. I'd use 2 coats of this and do a guide coat with cheapo different colored primer, just fog it on lightly. Then wet sand lightly with 400. This will show you any peaks and valleys that need attention.

You really shouldn't need any body fillers on the bumper but may want to get some glazing puddy.
I personnally like Evercoat products and they do have some Corvette specific products like SMC compatable fillers.

Bill covered it - that's just about the exact procedure I use. 220 DA, repair any damage/imperfections with a good quality filer approved for flexible covers then 220 block followed by 400 block. I don't usually go higher than 400 but you are certainly welcome to if your paint system's "P" sheet (product sheet, available upon request at your local paint supplier) allows it.

I usually use PPG paints. As Bill mentioned for repair of SMC panels Evercoat makes a line of products developed specifically for SMC panes. SMC is different in many ways from traditionally hand laid fiberglass but the major issue with repairing SMC is that SMC is impregnated with mold release agent when it's made so, a special compatible filler must be used or problems will arise down the road. Always be sure the filler is for use with SMC. The C4's body panels are all SMC fiberglass.

I *believe* the C4's bumper covers are urethane. There are many different variations of the plastics used today by different manufacturers for their flexible bumper covers but I believe the C4 is urethane. The factory manual should tell the exact material in the body section. At some point it became mandatory that manufacturers stamp a 3 letter code on the inside of bumper covers to denote the exact material the cover was made of. I believe the C4 was before this time though. For flexible bumpers I use use following products both with great success and never a failed had a repair fail in 10+ years:

SEM Carbo Fill. Some of SEM's repair products are here:

http://semproducts.com/Catalog.asp?cat=58

Another good product I've used to repair small damage on flexible bumpers:

http://www.evercoat.com/productDetail.aspx?pID=8

Be sure to follow the directions provided by each product and use any additional products they suggest in the prep/repair of the panel.

Good Luck with your project,

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I really like PPG too. On the racecars, the chip resistance is very good. The only one that's better (IMO) is Emron.

Brian, have you tried any of the PPG water based stuff yet?

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Haven't tried he water based stuff yet. We have no restrictions on paint here in VT so, I continue to use what I know and am use to.

I am curious to try a water based paint at some point but I know very little about it and don't do nearly as much painting these day as I used to.

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The only thing I see is that the gun is supposed to have stainless steel internals.

I don't paint too much anymore either, just the 50/50 stuff (racecars).