Repair & Refinish Interior Plastic Pieces (black)

Technical Information Bulletin Rev. New 5-7-01

How to Repair & Refinish Interior Plastic Pieces

(stolen from the desk of : ) by Lars Grimsrud

Colorado Corvette Crazies (CCC)

The Ultimate Corvette Tuning & Beer Drinking Fraternity

Lafayette, CO

Having seen some pretty rough-looking ‘Vette interiors, and some rougher-looking ‘Vette interior repair & refinish jobs, I thought I’d put together a little how-to on making your black plastic panels look better than new again.

Supplies needed:

(All supplies are available from most automotive paint supply stores. I have had very good luck with the PPG stores and dealers)

1 qt can PPG Wax, Grease & Silicone Remover (part # DX330)

1 gal PPG Vinyl Prep/conditioner (part # DX103) or -

1 pt bottle SEM Plastic Prep or SEM Vinyl Prep (part# 38348)

1 aerosol can SEM Original Trim Black Trim Paint (part # 39143)

1 aerosol can SEM Vinyl & Plastic Color Spray (part # 452340)

1 kit SEM Rigid SEM-Weld II plastic repair compound (part # 39508)

Lint-free paper towels (available in big, cheap bundles at the paint supply store)

Tack cloth

600-grit wet-or-dry sandpaper

Grey Scotchbrite pad

The black plastic dash and console panels in your C4 are not bare plastic. The are coated with what GM calls “Dulso.” This is what gives them the unique satin black appearance, but it’s also what makes them difficult to keep looking nice: as you rub and clean them, the Dulso wears off, leaving shiny plastic areas. The Dulso also stains if you spill things like acidic soft drinks on it, like Mountain Dew. A good refinishing process is certainly needed…

Before starting an interior refinish job, you need to be aware of the single biggest problem with interior parts: Silicone contamination. Interior “care” products, such as Armor-All, Son-Of-A-Gun, and others, contain HUGE amounts of silicone. Once this had been sprayed on interior parts, it is extremely difficult to remove. Silicone is a painter’s worst nightmare: even the slightest amount of silicone will cause primers and paints to “fisheye,” separate, and loose adhesion. Not good. in order to do a good plastic refinish job, we must first address preparation and silicone removal.

Silicone cannot be removed by sanding or abrading (like with a Scotch-Brite pad or SOS pad). In fact, any attempt to sand or abrade the parts to clean them will embed the silicone into the parts, and you will be doomed to failure. DO NOT sand the parts before doing a good cleanup on them. First clean the parts in hot water with dishsoap in it. Use a sponge (something non-abrasive) and put some effort into it. Rinse them off and dry them. Dump out the contaminated water and don’t use it again on the parts. I have an automatic parts cleaner at my house: my wife thinks it’s a dishwasher, but I know it’s an automotive parts cleaner. Just turn the drier heat “off” before running your plastic parts through it. I leave the heat “on” and put it on the “potscrubber’ cycle when I run rods and pistons through it (I don’t understand why this upsets my wife: don’t they advertise that these machines remove caked-on grease…?).

Next, use your silicone remover, following the directions on the bottle. You will soak a lint-free paper towel, wipe once in one direction, flip it over, and do it again. Then throw that towel away and do it again with a fresh one. If you wipe back and forth with the same towel, all you will do is smear the invisible silicone all over the parts with no gain. So do the one-wipe thing and use up some of those cheap towels you just bought. Once you’ve done this several times to all the parts, give them a wipe-down with the grease and wax remover, using the same technique.

The parts should now be about as contaminant-free as they’re going to get. If they have nicks or etched-in imperfections, you can now use some sandpaper or Scotchbrite to smooth them out. If they are cracked or damaged, clean the damaged area with the SEM Plastic Prep and use the SEM-Weld II two-part plastic repair kit to fill the damage and sand it out like body filler. It sands really nice, and is easy to form. If you sand the parts, make sure that the parts do not have a finish any coarser than a wet 600-grit finish when you’re done: anything less (even wet 400-grit) will leave visible scratch marks in the finished product.

Final prep step is to clean the parts completely with the SEM Plastic Prep or Vinyl Prep. This stuff actually slightly softens and dissolves the surface of the parts, and makes the surface “fuse” itself to the paint you will apply. So don’t rub aggressively with these prep products: follow the label directions and give the parts a gentle wipe-down. Rinse with water. If your parts are perfectly prepared, the water will “sheen” off the parts and will not separate or “break.” This is known as a “water break free surface condition,” and indicates a contaminant-free, clean surface. Dry the parts.

The SEM Trim Paint is actually an exterior trim paint product, but it works perfectly on the ‘Vette metal parts in the dash, like the lid for the cup holder. The Vinyl and Plastic Color Spray is to be used on all of the plastic parts. Lay out your parts and lightly go over them with the tack cloth to remove any dust or particles. Apply the first couple of coats of paint very light and fairly dry, in a criss-cross pattern to assure coverage. Observe if you are getting any fish-eying or separations. If you are, the areas that are fish-eying must be coated with VERY light and VERY dry coats at first until they are covered with the paint, allowing the paint to dry between these coats. Be patient. Don’t try to cover it all with a big wet coat at first. Once you have complete coverage with your light mist coats and this has dried to a tack-free state, lay down two medium, even coats. This will give you a perfect, even, beautiful sheen to your parts.

Install the parts back in your ‘Vette and admire how good of a painter you are!

For additional info on SEM products, or for a distributor near you, contact them at:

SEM Products 1-800-831-1122 or check on-line.