Model master paint coming off

[trainjk]

I'm working on a HO scale Kato dash 9 and I painted the sideframes and tank and then when I was putting it back together I noticed the paint was slightly rubbing off so I decided to clean all the paint off and start over. So I recleaned all the parts and started over and now just to test it I started rubbing on the paint to see if it was any better and I think it still rubs off to easy.This is my first time using Model Master paint so I'm wondering if its the paint, by the way I'm using a airbrush, any help would be appriciated.

 

[diburning]

It could be the type of plastic they used on the model. Delrin, which is commonly used for trucks and handrails, is more flexible, can be handled a bit without breaking, and can be molded finely so that something that's scale sized can still hold its shape without being brittle.

Athearn uses delrin in their trucks and handrails. Atlas uses them in their trucks. Delrin is a slippery plastic that repels paint, which is why it is often molded in a specific color rather than painted.

ABS (engineering) plastic is also used in some cases. ABS does not take to paints or glues very well although paint will still stick (somewhat).

I'm not sure if Kato uses delrin or ABS on their trucks, but I highly doubt its the paint.

When do you rub the paint? Do you let it dry thoroughly (no paint smell) before you rub it? Do you clear coat it? If so, did you wait until the base layer of paint dried thoroughly before spraying it? Paint can react to clear coats if applied before the paint is completely dry.

 

[RW&C]

Did you use a primer? If the plastic is clean and shiny, some paints won't stick too well. I've also heard of something called 'plastic prep' which might help.

 

[trainjk]

Did you use a primer? If the plastic is clean and shiny, some paints won't stick too well. I've also heard of something called 'plastic prep' which might help.

Yes the paint was shiny silver but I cleaned it very well and soaked it in warm soapy water then scrubbed it again and rinsed it as good as I could.I didn't use a primer because I thought "primer" was just a different color in this type of paint.

 

[trainjk]

It could be the type of plastic they used on the model. Delrin, which is commonly used for trucks and handrails, is more flexible, can be handled a bit without breaking, and can be molded finely so that something that's scale sized can still hold its shape without being brittle.

Athearn uses delrin in their trucks and handrails. Atlas uses them in their trucks. Delrin is a slippery plastic that repels paint, which is why it is often molded in a specific color rather than painted.

ABS (engineering) plastic is also used in some cases. ABS does not take to paints or glues very well although paint will still stick (somewhat).

I'm not sure if Kato uses delrin or ABS on their trucks, but I highly doubt its the paint.

When do you rub the paint? Do you let it dry thoroughly (no paint smell) before you rub it? Do you clear coat it? If so, did you wait until the base layer of paint dried thoroughly before spraying it? Paint can react to clear coats if applied before the paint is completely dry.

I let it dry completely before I rubbed it and this time I didnt put any more coats of anything on top just to make sure there was no reaction with the paints.The problem is I'm trying to weather it and make it look old and if the paint rubs off ,the shiny paint underneath is going to ruin the whole effect I'm going for.

 

[trainjk]

Does anybody else have any advice? I'm thinking of trying some floquil primer next and see if that sticks, I also have some polyscale paints, let me know.

 

[wheeler1963]

If you have a gloss coat of paint underneath it, you'll need to rough up that surface to give the new paint something to hold on to first.

 

[trainjk]

If you have a gloss coat of paint underneath it, you'll need to rough up that surface to give the new paint something to hold on to first.

Thats the problem there is way to many detail parts to get in there and scuff it up

 

[wheeler1963]

Two ways that I know how to do that. Media blasting or use a Mr. Clean magic eraser.

 

[Cjcrescent]

I would also look at the paints used on Lexan RC car bodies. This paint is designed to stick to flexible plastic/nylon type materials. Its available in many colors, and a bottle will last quite some time. I use it on diesel handrails, fuel tanks, etc anywhere there is a delrin, celon(?), nylon type material is used. Also since the paint itself is flexible, it won't crack when flexed.

 

[tomstockton]

Correct me if I'm wrong, but doesn't primer have more "tooth" to adhere to the surface being painted AND a better dried surface for the following coats of paint? I almost always prime first, usually using a light gray (Floquil).

And I suppose if some did rub off, you could cover it with weathering chalk / powder to "hide" the places where the paint rubbed off. That might work...

Regards,
Tom Stockton

 

[Cjcrescent]

Its been my experience Tom, that on some of the engineering plastics, not even primer will grab it any better, that's why I use the Lexan Paints, on these parts when painting them. It doesn't rub off, as its designed to stay on the RC body without cracking, even after the body has hit something, deformed and popped back into shape.

 

[tomstockton]

Very true, Carey, very true. But I've noted that I've run across both plastic and cast metal parts where it seems like the primer has made some difference. Maybe it's my imagination... but I still prefer to use primer.

Regards,
Tom

 

[sd50f]

Athearn trucks, at least on their locomotives, have either been cast zinc or polystyrene. They don't use delrin (I think I learned this from Brian Banna).

I'd scrub them with some kind of cleanser, and then wash them over and over again until the residue is gone. Then I'd prime and paint them.

Timothy Dineen

 

[Cjcrescent]

Very true, Carey, very true. But I've noted that I've run across both plastic and cast metal parts where it seems like the primer has made some difference. Maybe it's my imagination... but I still prefer to use primer.

Regards,
Tom

When I've painted loco's for myself and others, on all the parts made out of styrene plastic, zinc, or brass, I have always primed them. But on these engineering plastics, unless the primer can etch the plastic some, I have found that regular paint and primer doesn't stick well period. Even stored in their original boxes, places like the spring ends on the trucks come out of the box, all nice and shiny and black.

The Lexan paints stick much, much, better to these areas, and do not rub or flake off. Put a primer underneath them, and they do. This has happened on my own few diesels as well as to others I have painted over the years, until I found the Lexan paints. Somehow I think they do "etch" the surface, and therefore are more durable. I definitely know they are flexible.

 

[Cjcrescent]

Athearn trucks, at least on their locomotives, have either been cast zinc or polystyrene. They don't use delrin (I think I learned this from Brian Banna)...

Timothy Dineen

Back when the Athearns were still made in the US, Athearn did use delrin on the loco sideframes. At least that's what said on a tour of the plant in 1980. Apparently, it was cheaper to use the same plastic the gears, the freight and passenger trucks were made out of, which was delrin, instead of having to order, and store another type of plastic on the premises. During this time, some of the locos suffered from "sideframe" loss when running. The sideframes would fall off the locos while they were running due to the plastic being so slippery it couldn't grip the trucks well enough to stay in place. I had an SD40-2 that was bad about this.

Once production moved offshore, materials may have changed.

The truck sideframes were once cast zamac, but with the release of the SD40-2s in the late 1970's, they starting converting all their locos to inboard bearings and plastic sideframes.

 

[Mark R.]

Go to your local automotive paint supply store and get yourself a spray can of Adhesion Promoter. This is what body shops use on flexible rubber bumpers and other parts to aid in paint adhesion. Also works well on delrin handrails !

The trick being - you must get your paint color down on the adhesion promoter before it sets. I usually spray my color on within a couple minutes while the adhesion promoter is still wet. This way the paint melds with the adhesion promoter. Once the adhesion promoter gets tacky / dry - it's as good as none at all and you'll have to re-coat. I've painted lots of side frames and handrails using this method and have yet to have a paint peeling problem.


Mark.

 

[trainjk]

The only reason I'm trying to not use primer is because I'm not really painting them, I'm just trying to put a light wash of paint to dull them and make them look older,then I'm putting on a couple other colors to dirty them up. But I'm trying to figure it out before I paint the shell this weekend, and and going to do the same thing with the paint. I don't want to paint it but more like just fade the paint and make it look dirty. I did look at my LHS for the lexan paints because I've heard of that before but I didn't see any colors that looked like they would work or any primer and I didn't know if I could mix the two types of paint even if I did find some that would work.

 

[Cjcrescent]

Take the black and mix it with equal parts of dark gray. This should give you a type of grimy black. then you can apply dull coat over it to add more weathering to the sideframes. These paints don't really need primer.