Hard Body Paint Not Sticking Well

[Hakizi]

I'm painting an RC4WD Hilux (so a hard body) and used Krylon paint that's for plastic. I scuffed the body with some fine sandpaper, washed it with dish soap and rinsed it like crazy to make sure there was no soap residue. Then I used primer first, then painted the underside (haven't done the outside yet), and for a test scratched it with my fingernail and to my surprise the paint and primer came right off. The paint and primer were both left in outside in the heat to dry at ~90 degrees for several hours initially, then left indoors to dry for a day.

Is this because there's not some kind of clear coat over the paint yet, or did I just totally botch the painting?

[Ditchrat]

Scuffing and soap do not adequately remove the mold release agent, who job is to not allow things to stick.


It needs to be chemically cleaned. However I have had great success washing bodies in a dishwasher with cascade. Just don't use the heated dry.

[whitrzac]

I've had issues with krylon not curing or drying on parts recently. I use other paint types now.


Hobby lobby has a good selection of model paint if you have one localy

[TooOldForThis]

I've had excellent results with Tamiya's spray paint for plastics (not polycarbonate). I didn't do any more prep work than the OP did.

[4wd4ws]

Did you scuff the body before cleaning it?

[Hakizi]

Originally Posted by 4wd4ws

Did you scuff the body before cleaning it?

Yes

[4wd4ws]

No bueno.

Clean, scuff, clean.

When you scuff first you rub the greasy stuff in and create a non penetrable barrier.

Remove the paint, which should be easy and submerge the body in soapy water and take off the shiny/yellowish layer on top of the plastic. (scotchbrite maroon)

It's time consuming and a total pain but if you take your time you will not ruin the lines and details and nobody will ever know you took a detour.

[Hakizi]

Originally Posted by 4wd4ws

No bueno.

Clean, scuff, clean.

When you scuff first you rub the greasy stuff in and create a non penetrable barrier.

Remove the paint, which should be easy and submerge the body in soapy water and take off the shiny/yellowish layer on top of the plastic. (scotchbrite maroon)

It's time consuming and a total pain but if you take your time you will not ruin the lines and details and nobody will ever know you took a detour.

Any tips on removing the paint and primer easily? I'm thinking sanding it off will have a lot of potential to mess up the details on the body.

[mond]

You can use progressively finer paper, you can go as high as 1200 grit cloth sheets. Any imperfections can be in filled with something like Mr Surfacer. It's pretty common to do that on model kits.

[4wd4ws]

Originally Posted by Hakizi

Any tips on removing the paint and primer easily? I'm thinking sanding it off will have a lot of potential to mess up the details on the body.

If you can scratch it off with your fingernail you should have no problems taking it off with scotchbrite. (maroon)

[struhall]

I use scotch brite to sand the entire body and then wash it real good. Once it's good and dry I use spray paint primer then sand again and then the color.

I also like to use the cheapest spray paint available at Walmart. It's something like a dollar or 2 per can. I have better luck with that than the expensive stuff labeled specific for plastic.

[Natedog]

Originally Posted by Ditchrat

Scuffing and soap do not adequately remove the mold release agent, who job is to not allow things to stick.


It needs to be chemically cleaned. However I have had great success washing bodies in a dishwasher with cascade. Just don't use the heated dry.

Originally Posted by 4wd4ws

No bueno.

Clean, scuff, clean.

When you scuff first you rub the greasy stuff in and create a non penetrable barrier.

Remove the paint, which should be easy and submerge the body in soapy water and take off the shiny/yellowish layer on top of the plastic. (scotchbrite maroon)

It's time consuming and a total pain but if you take your time you will not ruin the lines and details and nobody will ever know you took a detour.

Originally Posted by 4wd4ws

If you can scratch it off with your fingernail you should have no problems taking it off with scotchbrite. (maroon)

Wow, not had this much trouble painting (yet) but got my first hardbody TF2 and this is great information, thanks!


Scotchbrite maroon pads:
https://www.3m.com/3M/en_US/company-...3241244&rt=rud

[lilws6]

I've had great luck lately with Duplicolors adhesion promoter. I've done as others clean scuff clean again then use the adhesion promoter then prime and paint then clear. The paint and clear will come off with enough abuse but the primer stuck to the promoter has not come off unless properly dragged across some rocks ;) i got mine at advance auto got the idea from my painter at work. heres a link to what i'm talking about. https://shop.advanceautoparts.com/p/...esion+promoter

[mewalsh100]

Once you're done scuff sanding everything, wash it with simple green (or Dawn dish soap). Allow it to thoroughly dry. (If you're in a hurry, you can aid this with a hair dryer). Once it's thoroughly dry, wipe the whole body down with isopropyl alcohol, paying close attention to all the little creases and crevices. From here on out, only handle the body while wearing latex gloves so you don't transfer any of the natural oils from your hands to it and contaminate it. Now you can prime it. Let your primer set up for at least 24 hrs. Once the primer is completely dry, put the latex gloves back on and shoot your color. The key here, with both the primer and the color is to to build it up using dusting coats. If you try and get either done in 1 or 2 spray sessions, it's not going to adhere right. My Hilux gets absolutely thrashed on and the paint is holding up well. (I used Rustoleum brand for plastics). It has the usual scuffs and scrapes from the rocks, but most of those are only through to the primer. Painting is always a game of patience. Good luck with your rig and post some pics of the finished product!

[Jim85IROC]

Using a paint made for plastic is completely unnecessary if you're using a primer. The primer needs to stick to the plastic. The paint just needs to stick to the primer.

[Shinchu]

this is all great stuff... is this stickied somewhere?? im about to get my son a hardbody and i can already see i would have made mistakes had i not read this.
along the same lines, i would assume all this prep even before cutting a body and modifying with styrene would be a good idea so you aren't smearing mold release all over when sanding your parts and gluing them?

great thread, thanks OP for asking the questions!

[Ditchrat]

Originally Posted by Jim85IROC

Using a paint made for plastic is completely unnecessary if you're using a primer. The primer needs to stick to the plastic. The paint just needs to stick to the primer.

You are not supposed to primer on plastic paints, they are designed to react to the plastic and fuse to it.


If you are using primer then you just need paint. The idea behind plastic paints are flexibility and chemical adhesion. There is a huge difference between a paint that say can be used for plastics and one that is made for plastics. The former won't melt the plastic and is plastic safe, the later is made to bond to plastics.

Originally Posted by Shinchu

this is all great stuff... is this stickied somewhere?? im about to get my son a hardbody and i can already see i would have made mistakes had i not read this.
along the same lines, i would assume all this prep even before cutting a body and modifying with styrene would be a good idea so you aren't smearing mold release all over when sanding your parts and gluing them?

great thread, thanks OP for asking the questions!

Don't even bother. Cut up your body. and modify it. The styrene bonding agent is about the best cleaner you can get, in fact I use pipe clean to glue styrene and ABS. Once you finish, toss it in the dishwasher alone with cascade, turn off the heated dry and run it through a cycle.

You will get the cleanest, best surface you have ever worked with. oh and try to not get oily finger prints on it.

[Mike Flea]

I don't know, I treat all styrene bodies the same. Scrape and sand the mold lines for a smooth surface, wipe it down with a soft cloth, and blow off the dust, prime with Testor's grey primer and shoot a couple coats of the final color. Never had a problem with orange peel or flaking paint in 50 years.

Y'all are overthinking this.

[Chiphead]

This may explain some of my troubles. For a winter project I bought a RC4wd D90. I went through hours of bodywork etc... only to be very disappointed in the fragility of the paint. I did wash the body, but not much more than a rinse off. I did use an scotch bright pad on some of the surfaces. I used Tamiya primer and paints. The paint is very fragile, barely touching a rock the scratch will go down to the plastic.

[WranglerMan]

The first time I painted my TF2,I didn't wash the body before the prep work. I prepped the body like I would a 1/1 sand,prime,sand and then wash and I can say that I spent about a day and a half getting it ready for paint on the count of filling imperfections. I used Tamiya acrylic paint in the 1/3 ounce bottles so that I could use my new airbrush,but it was wasted time and effort on the count of the paint was getting scratched off easily. Maybe I didn't prep the body correctly or maybe it was because I used automotive primer and Tamiya paint? Anyway I was dissatisfied and I decided to repaint using Krylon OD green and so far it's holding up really well. Isn't amazing how much time we hobbyists put into these little trucks,