Plastic Parts

[newbie]

I need a little help. I'm preparing my m/c parts for painting. I've got the side covers and front fender (both plastic) ready (sanded with 320) for priming. Since I will shoot the bare metal tank and rear fender with Epoxy Primer, (at a later date), I would like to shoot the plastic with the same. Anything I should do to the plastic first? Would I be better with a 2K primer on the plastic? Thanks in advance for any help.
grateful newbie

 

[rex]

What system are you using?That will make a difference.For epoxying the bare steel it would have been better to sand it with 80-120 to get an agressive tooth for the epoxy to grab.You should be fine but sand thru a spot and put line pressure to it to see if it'll lift,then just blow a little more on that spot.A plastic primer should be used on those pieces and epoxy will be fine but what happens then depends on the system as far as dry time and sanding.

 

[newbie]

Rex,
Thanks for the prompt reply. I haven't shot the bare metal yet, so I'll sand it first with 80 grit. If I wait a few days, will the epoxy dry to a sandable hardness? Also, after allowing the epoxy to dry hard and sand, can I shoot my first base coat right on the hardened epoxy? I'll be shooting a Urethane, 2 part, probably Dupont. I found a DP40 tech sheet, that states you can reduce the primer with DT or DTL Reducer to make it useable on flexilble parts, have you heard of that before.
Do you think that would apply to all epoxy primers, the reason I ask is, I bought Nason Brand Ful-Poxy Epoxy Primer.
I know this is a lot of questions, and I appreciate any help I can get.
Thank you,
newbie

 

[rex]

On the bare steel,sand it really well since you're down here in Fla too,the weather has been nice but rust starts pretty much immediately.You might not be able to see it which is good,it's so thin a good 80 gritting will remove it.The best thing to do is hit the paint store up for a sheet on the Nason epoxy to get it's info,DP from PPG is an unusual epoxy with traits different than any other I've seen or used.On the steel you should be fine letting it dry and sanding then basecoating.I would prefer to 120 the steel in this case to minimize scratch size,then spray a good coat of epoxy and a guide coat right after it flashes.Then sand with 600 until the guidecoat is just gone so you don't sand it too thin.Thinning the epoxy is to reduce it's thickness for flexibility or for using as a sealer.On the plastic parts I would put a coat of plastic primer on (you usually don't have to but it is great insurance) then put a coat of reduced epoxy on but not to sand it,use it as a sealer sprayed on before baseing to save some work.Oops,you said you already sanded them with 320 so I'd put a coat of reduced epoxy on to sand,320 can make a large scratch in plastic.Sand these good so you're removing alot of it unlike the tank,then spray a coat of reduced epoxy over it for a sealer.With whatever's left over spot spray any edges on the steel you might have broke thru to steel and paint away after it's flashed.I'm assuming this epoxy will work this way so get a sheet to double check.Hope i didn't confuse you.

 

[newbie]

Rex,
I need a little more clarification, Please. You're saying since I've already sanded the plastic, to go ahead and shoot a reduced epoxy on it. If I get a good sanded finish on that, why do I need to shoot reduced epoxy again as a sealer just prior to my base coat? I'm certainly not questioning your knowledge, just trying to learn?
Thanks,
newbie

 

[rex]

Well,I suppose it depends what's left after sanding and the type of plastic it is.The thinned epoxy will be thinner and 320 on some plastics looks like 180,so after sanding not only could the primer be extremely thin but the scratch 'swelling' might be broken through after sanding so another coat used as a sealer would be good for a thin barrier coat to prevent any swelling or shrinkage on breakthroughs.It will also give you a reason to touch up spots on the tank like the edges of mounting tabs that easily get sanded thru while prepping since you have a few drops left in the gun.Of course you can blow a straight coat of epoxy on the plastic and sand it really good but Murphy's Law just about always bites you and you'll bust through somewhere (like the tank tabs) and you'll need to touch that spot up anyway.Sorry for the confusion,the meds make me wierd-I'm used to beer instead of being forced to take perscriptions.Actually looking back at some old posts the beer ones got out there sometimes too /ubbthreads/images/graemlins/foreheadslap.gif

 

[newbie]

Rex,
Thanks for clearing that up. Here's an easy one, probably sounds stupid. Do you thin the epoxy (or any paint for that matter) before or after mixing it with the catalyst?
Thanks again, you've been great.
newbie

 

[rex]

I dump it in first and everyone says too........and I understand what they're saying but I don't believe 10 seconds matters and never had a prob reversing it.Where you at in Fla?

 

[newbie]

Rex,
I don't know what the 10 second rule is you're referring to. So you're saying you put the thinner in first?
I'm in Cocoa Beach.
Thanks,
newbie

 

[rex]

Yeah,I add it before the hardner,at least 99% of the time.The 10 seconds I refered to was the amount of time it takes to pour in the hardner,set it down and pour in the reducer,or vice versa.They say adding the hardner first shortens the pot life because it starts reacting but I don't see that 10 seconds hurting anything,all the clears I use have ample pot life to get the job done.I'm also known for mixing up enough to do the first coat and then mix more for the next coat to top it off so I see how much a coat actually uses,I hate guessing wrong and throwing away a pile of clear.Nice area you live in,that's down around Pompano below Lauderdale right?It's been yoars since I've been on the east coast,I used to live in the Stuart,Jensen Beach and Ft Pierce area about 15 years ago when I moved to Fla.

 

[newbie]

Rex,
Thanks again. Cocoa Beach is due east of Orlando. I'm about 75 miles south of Daytona.
I'm hoping to shoot some epoxy this weekend, temp is supposed to be a high of 62. Is it truly safe to shoot anything above 50 degrees? I know it will be slow drying, but since I'm just shooting epoxy and letting it dry to a sandable hardness, will I be O.K.
Thanks,
newbie

 

[rex]

Boy,I was off on that eh?Go ahead and shoot it,just remember it's cold so you don't slide it.If the sun's out I sit it outside to warm up and pull it in the shade long enough to shoot a coat and stick it right back out there to flash.This is where a magnetic or infrared(?) temp guage really comes in handy for reducer selection if it's used.I'm not positive about all the different paintlines and the socalled speed hardners but I go by the PPG's rule that under 60 chemical hardening stops.If you're at home just bring it inside to dry but if you're at the shop you're kind of screwed.Those expensive heatlamps work wonders but they sure will melt down a plug if you run them long but the real expensive IR(?) lamps will cure it out pretty fast,longer than a bake booth by about 50%.Kind of ironic a heated booth would be needed in Fla but it does get cold here.Not a good topic to bring up to a citrus grower.