Interior painting.... OOOPS!

[chengny]

It doesn't matter whether you use SEM or Duplicolor as the final trim coat - I get similar results with either.

What does matter is the prep process. It is time consuming and tedious. But without proper preparation, the surfaces to be coated will not accept the finish coat.

Anything on the substrate HAS to be removed, leaving only the raw vinyl. Use acetone or MEK. MEK is better, but is getting harder to find - many places only sell MEK Substitute now (take acetone over the MEK sub if that is the choice).

Using the solvent and a stiff scrubbing brush (not steel wires - only with nylon bristles), be meticulous and get everything off.

Many interior parts have a grained surface and these areas can be especially difficult to clean completely. The grime in the deepest parts of the grained surface will eventually come out but can be a real struggle. It helps if you continuously change the direction of the scrubbing motion. Also the bristles of the scrubbing brush may be too thick to reach down into the grooves. It this is the case, you may have to get one with finer bristles. In extreme cases, you might even have to use a brass wire brush - use it gently and try to follow the grain of the pattern.

When you have the substrate completely stripped, wash all surfaces thoroughly with warm soapy water. Rinse well and let dry. When all dry give a final wipe down with acetone/MEK.

Plastic Adhesion Promoter:

This step is vital and cannot be omitted. Again, the SEM and Duplicolor products perform equally well if properly applied:



To ensure a bond between the substrate and finish coat the plastic substrate must be "softened up" to a certain degree. There is no paint made that will adhere to the ABS plastics used to manufacture automotive panels.

This is where the adhesion promoter comes in. When applied, it temporarily breaks down the surface of the plastic and melds into it. Consequently it creates a new, uncured surface that will accept the trim paint.

There is only a very small window of time (maybe 20 mins) during which the adhesion promoter has had time to integrate itself with the plastic substrate (on the lower surface) - and yet remains wet enough (on the outer surface) to accept the final color.

After the cleaning process is complete, gather all the materials needed to prep and paint the plastic. Have them close by. You will have only 1/2 hour to get both steps done.

When the adhesion promoter has "flashed off" but is still slightly tacky, apply the trim paint. As always use long sweeping motions. Keep the can in the vertical position only with the nozzle approximately 12 inches from the work. Warm the paint in a hot water bath before application starts. This will help atomize the paint (producing a finer mist that lays down more evenly) and also helps maintain a consistent spray pattern.

Apply two light coats and a final medium wet coat. A couple of minutes dry time between each application is sufficient.

If the job is done as described above, you can expect a paint finish that closely approximates a factory look.

One word of warning: Before starting, consider the physical condition of the plastic substrate. Is it cracked? Is it crumbling and pitted from exposure to the sun? Has the surface texture of certain areas changed over the years so that they no longer match their surroundings? This happens frequently on the upper surface of door panels for example. Years of driving around with the window down and your arm resting on the plastic will wear it to a smooth surface that no longer looks like the rest of the door.

Even the most meticulous prep work, use of the best paints and perfect application techniques will not make a physically damaged plastic panel look anything like new.