Paintin' plastic - PeachParts Mercedes-Benz Forum

Stretch · #1 06-28-2014, 03:39 PM

G'day Folks,

Now I have a plastic fantastic modern car (W201) I guess it is time to make sure I'm repairing scratches in plastic in the best possible way.

Here's what I've been doing so far.

If anyone thinks there's a better way please let me know.

Although I've "done" the bumper I'll be moving on to other stuff in a bit so tips and advice are still needed!

Here's an example of the damage I'm trying to fix

This is a definite "I've just rubbed up against a concrete wall" type of a scratch - it is quite deep and hairy.

I degreased the bumper with engine degreaser - then I wiped off the excess with thinner. This was a bit dodgy I didn't want the bumper to go sticky so I took it really easy...

Here's using a sanding machine to get rid of the worst

This is the other end of the bumper (after a bit of machine sanding) that had the same cement wall treatment

Back to the left hand side again - this is after a bit of block sanding with 240 grit - area has been cleaned with water.

Stretch · #2 06-28-2014, 03:45 PM

I got two types of filler a hole filling one and a smooth filling one.

Applying the hole filling one sparingly

Then after sanding and some fine filler and some more sanding

After the same treatment on the other side

Stretch · #3 06-28-2014, 03:52 PM

Only rattle cans today I'm afraid.

First a plastic primer after wiping down the bumper with Eastwoods pre-paint and masking the bit I don't want painted (will be covered by a black bumper strip)

The colour code of this bumper is 7700 Alto gray

Here it is going on

There's a bit of a colour mismatch

Not too too bad colour wise.

Up close I can see I need to add on a layer of spray primer and finish off the sanding with a finer grade paper

Has anyone got any other tips?

Should I have added the special plastic primer before the filler?

oldsinner111 · #4 07-01-2014, 04:38 PM

I heard a fexible bumper paint it the way to go.If not plasti dip might work

Stretch · #5 07-02-2014, 02:50 AM

I'm not happy with plasti-dip especially from spray cans it gives a very furry / speckled surface that collects dirt. Besides the factory parts are all sprayed with normal car paint - I haven't hear about flexible bumper paint. I'll shop about for it - thanks for the tip.

jmk · #6 07-07-2014, 03:28 PM

Saw the Duplicolor can. Avoid that. Bad SW paint, and that is really bad. Avoid that! (also expect mismatches with Duplicolor. I used to call it Unduplicolor.)

Spent the first three years making OEM bumper paint, though I know nothing about bumper refinish. The better refinishes are urethanes, and I think they add a polymer to make the urethane more flexible.

On the OEM side, GM used to develop their base coats to spray over both the bumper and the body, then had different clears for each.

The only thing that I can add of value is to use a real gun, and not a spraycan.

Stretch · #7 07-08-2014, 12:27 AM

Well thanks for the warning about Duplicolour - I'll dig out the spray gun this weekend.

crazy4diesel · #8 07-16-2014, 12:01 PM

Krylon and some others have developed rattle can paint specifically for plastic. Including a clear coat. It's an option. I'm not saying it's professional though.

jmk · #9 07-21-2014, 10:38 AM

Krylon is also SW, though they tend to fill better stuff in those cans, though I really do not know about the automotive finishes marketed under Krylon. (Just to let you know, the Krylon marketed industrial 1k waterborne coating was way better than the one marketed under the SW brand.)

Yes, the Krylon cans actually make a decent fan pattern, and they are the one I use for home projects, but I would still break out the gun for a car.

Stretch · #10 01-18-2015, 09:11 AM

I have resorted to spraying the plastic with spray cans (so the colour match isn't top) under the veranda and then bringing the pieces inside to dry at room temperature...

...oh how I love January in Holland!

Covered in spray filler =>

Then the sanding

I get the feeling I should sand some more of the spray filler away - but hey - gorra crack on and get this fitted to the car

Drips from the spray can happened just the once

I'll be sanding them again then

Stretch · #11 01-18-2015, 09:59 AM

Final coat done - ever so slightly patchy but you kind of expect that from paining in the snow with a spray can

It is probably going to be good enough to fit now - I'll see what it looks like when it is on the car.

jmk · #12 02-12-2015, 03:03 PM

Stretch,

It is really pretty good. These panels were never meant to match. Matching body to bumper is very hard (look closely at a modern car, and you'll see what I mean), and the technology to do a decent job did not really come about until the early '90's (I was actually a part of that leap in technology.).

The only suggestion is that the panels do look mottled. Look at them closely, and you see the variation in color. Try adjusting the air/paint ratio on the gun. Usually a little wetter (more paint, less air) helps this.

Stretch · #13 02-13-2015, 01:25 AM

Quote:

Originally Posted by jmk

Stretch,

It is really pretty good. These panels were never meant to match. Matching body to bumper is very hard (look closely at a modern car, and you'll see what I mean), and the technology to do a decent job did not really come about until the early '90's (I was actually a part of that leap in technology.).

The only suggestion is that the panels do look mottled. Look at them closely, and you see the variation in color. Try adjusting the air/paint ratio on the gun. Usually a little wetter (more paint, less air) helps this.

I think the mottled effect in the pictures is partly due to the flash on my point and shoot camera and the paint (which is metallic). I kept on painting until I couldn't see any colour variations when I tilted the panels at different angles in sunlight. I also checked them under a strip light when it was dark too because sometimes that shows up flaws that you can't see during daytime.

Directly after spraying, when dry, the paint did feel a little powdery to the touch but a buff with a bit of toilet paper smoothed it all out. Would I need more paint (from a gun) to get it to spray without this powdery effect?