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shawnmc

Tamiya Bruiser paint peeling question

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I painted the truck bed. Sanded the plastic body with 1000 sand paper. Washed the body with dish washing soap. Used Tamiya primer let it dry for a day and painted the Tamiya color over it. Let it dry for a day. While masking to paint the rest, I noted that the paint is peeling off the bottom. What did I do wrong? Why isn't the primer not sticking to plastic? Even the paint is not sticking to primer?

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How old is the paint and primer, did you give it a really good mix/shake before spraying? Also did you gently warm the cans up before spraying? Oh another thing, did you start with very light coats and build up from there? Just throwing out ideas, it seems very unusual for it to peel.

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Bought the paint from a local hobby shop in California. I mixed it very well by shaking say for 1 min. Does it require more?

I did not warm the cans, Its winter time here in California. I sprayed this in the garage closed doors in a master spray paint booth with an exhaust fan but the temp outside could have been in the 50s or high 40's I am not sure F. Started with primer light coats gave it like 3 primer coats. Did not sand the primer surface. Then gave like 3 paint coats. Came out near perfect but it stated peeling from the bottom. Any thoughts? Is it the weather? If so then is it advisable to wait till Summer time. But that's 6 moths away :(

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Primer was Fine Tamiya gray primer. I noticed that they have regular gray primer as well. But the paint is also peeling from the Primer surface

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Is the primer peeling off? 

If you didnt key the primer before top coat the paint wont have stuck as well as it should.

You can lay coats down with 10 mins in between, but if the previous coat has set (a day or more) it needs keying before the next coat.

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Was the bodyshell completely dry and soap free before priming . If the temperature is cold I warm up the body shell slightly too before spraying

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Edges like that are always the hardest part and most vulnerable. Did you make sure you properly keyed the surface on the edges thoroughly?

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22 minutes ago, graemevw said:

Is the primer peeling off? 

If you didnt key the primer before top coat the paint wont have stuck as well as it should.

You can lay coats down with 10 mins in between, but if the previous coat has set (a day or more) it needs keying before the next coat.

Yes the primer is peeling off too. Key the primer means? sand it? No

 

 

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15 minutes ago, KEV THE REV said:

Was the bodyshell completely dry and soap free before priming . If the temperature is cold I warm up the body shell slightly too before spraying

Body shell was completely dry and soap free. I didn't warm up the body. How do you do that? Since it's plastic I do not know how to warm it up.

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3 minutes ago, graemevw said:

Edges like that are always the hardest part and most vulnerable. Did you make sure you properly keyed the surface on the edges thoroughly?

Keyed surface means? Sanding? I sanded the plastic with 1000 grit sand paper. Did not sand the primer. Is that what caused this?

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Just now, shawnmc said:

Keyed surface means? Sanding? I sanded the plastic with 1000 grit sand paper. Did not sand the primer. Is that what caused this?

Not sanding the primer may cause the top coat not to stick properly. If you missed any areas of the edge when sanding the body, easily done, then the primer may come off. You need to make sure every square mm is keyed really.

 

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I like to use scotchbrite pads when keying for paint as its alot easier to get all edges than when using sand paper. 

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I see. What can I now do to correct this? Sand it down to the plastic? If so what grit sand paper? Also do you recommend the Fine primer or the regular primer? what grid sand paper do I use to sand the primer?

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If your surface prep was as good as you say, it was probably too cold to spray.  Warm paint cans spray better. I use my hot tub to warm them to 100 degrees F

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do the same as you would if your blowing in a 1.1 car paint just make sure you can't fell a lip/edge to the paint and start over on the areas only with the primer and then fog in with the colour.

as i have said before this is why i won't use tamiya paint anymore

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What paint do you suggest? Automotive? Do they bond to plastic well? If so can you suggest a good brand Primer and paint?

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Assuming you're using TS paint there's nothing wrong with the products you're using. I and many others have used them without issues for many years. Using different paint probably won't solve your problem.

Non of the following is necessary if the temperature is suitable (if it was, the instructions for the paint and body would state it. It may give you a better finish but it won't cause the paint to flake off)

- Keying the surface
- Warming the cans
- Warming the body
- Sanding the primer

You don't really even need primer (again, Tamiya would say in the manual to use it if you did). I speak from experience because I've painted bodies in the most basic way possible and they've been fine. 

Your problem is either related to the temperature, your technique or how you've cleaned the body - maybe something in the soap you've used to wash it, or it wasn't cleaned well enough. Paint adhesion failure is usually down to a contaminated or unsuitable surface. The body is of course perfectly suitable so it must be something  else.

I'd run some tests on spare parts or bits of sprue - wash one bit and not the other, see what happens then. With two more bits paint one bit as you've done already, then paint the other bit by keeping the cans and the part inside where it's warm, stepping outside to spray, then bring them back inside again.

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On 1/12/2020 at 1:53 PM, shawnmc said:

What paint do you suggest? Automotive? Do they bond to plastic well? If so can you suggest a good brand Primer and paint?

i use wilco's white primer on my last 2 hard shells and had no problems with it and it only cost around £4 for a 4 or 500 ml can.

i only buy paint from https://www.specialistpaints.com/ and jawel paint these shell house of colour  and always get fantastic results i clear coat with 2k clear also.

i dont sand primer i only wash the shell as recomended.

i dont warm the cans and i have painted in both hot and cold temps .

i have had tamiya paint ruin a few of my shells plus whell arch fender flairs for my bruiser.

this is the finish with paint from specialist paint on the merc truck and jawel paint (house of colour on the grand hauler.

both only had shells washed and both finishe's are as they came from the can with no flating/sanding what so ever only used autoglym super resin polish on them

IMG_20180603_104528.thumb.jpg.7a4d3527d11c3d450600c748687102f5.jpg

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the 2k clear comes in can it aint cheap at around £14 to £20 a can but the results speak for them self

the can has a thingy at the bottom of the can that has to be pull'd to release the hardener that is in a seperate can that is inside the can (if that makes sence) then you mix the can as normal but you only get a hour or 2 to use it then what ever don't get used it sets and the can and leftover contents is then is scrap.

but in my experiance it goes on like glass and i have not had it orange peal either.

this is how it looks a day after painting

this IMG_20170705_163809.thumb.jpg.382ee89477000152717d77c6661715c2.jpgIMG_20170705_163858.thumb.jpg.e31975f3c52902c1b8fa4cf043b8d589.jpg

 

 

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2k give great results but  a lot of it contains Isocyanates which is very nasty stuff and requires a serious set up to be safe (ABEK2 filtered or ideally air fed mask, paint suit, thick gloves, proper air extraction systems etc). Do a lot of independent research before considering it and beware of retailers underplaying the dangers. A lot of places sell it with warnings no more severe than regular lacquers.

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Is it compatible with regular old halfords type car body paints and vinyl stickers etc or are the paints a different kind? Not heard of those brands brfore.

I bought some Halfords clear last year but it never seemed to go very glossy. That 2k looks amazing!!!

 

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