Basecoat/clearcoat strips away from epoxy primer.

[ebaypdllc]

Hey guys,

Quick question. I used another brand's Epoxy primer, (yeah I know)...I just ordered SPI EPOXY, in process of switching over to all SPI products. SPI arrives tomorrow.

Anyway this brand Epoxy is a 4:1 mix. In order to get it to shoot smooth, I added 30% slow reducer. It shot beautifully. I am shooting raw polyurethane plastic. The epoxy bonded 100% to the polyurethane. Even areas that were not prepped, it bonded. I did a "adhesion test", by cutting a grid with a razor blade. No issues whatsoever with epoxy bonding directly to the polyurethane without use of adhesion promoter.

I sprayed (2) wet coats, it laid out perfectly smooth and there was few nibs here. I epoxy primed the parts at night 10:00 pm. The next afternoon I wetsanded with 1500 and sprayed the base/clear.

I gave the basecoat/clearcoat 24 hours and wanted to do an adhesion test to make sure that bonded to the epoxy. Well it seems it didn't. I can easily strip the base/clear off the epoxy where I cut the grid pattern.

Is 24 hours enough time for it to fully "bond and cure" to the epoxy?

Attached is few photos.

 

[shine]

i see clear peeling off base.

 

[ebaypdllc]

Hrm, I did 3 coats of base 20 minutes between coats. Then SPI Production clear with slow hardener with 25 min flash time. Two coats.

I can just peel it off with a plastic razor blade pretty easily. Depending on the lighting, its almost like there is a very fine metallic left on the epoxy primer still, but majority of the base ripped off with the clearcoat. I tried taking different light angles. You can basecoat on the clearcoat as it peels off.

The SPI epoxy is coming tomorrow, i'll experiment with that...

I want to be able to shoot the SPI epoxy as flat as I possibly can and do few coats. How long before I can wetsand any nibs and base/clear without needs to completely sand the whole part? I've seeing mixed opinions on the forum. I think i'm going to go with a 25% reduction on the SPI?

Here is few more pics.

 

[crashtech]

24 hours is pretty soon, especially if there was any solvent trapping at all. I think you might have jumped the gun a little for your test. Do you activate the base? That will improve adhesion and flexibility.

I admire the fact that you are product testing.

 

[ebaypdllc]

Okay. I'll feel more comfortable using the SPI EPOXY. I like the fact that there is tech support on the forums

Yeah I just need to make sure these parts are perfect. I will be doing them in bulk, can't have any comeback's or issues. So i'm trying to get all the issues from A-Z covered.

I did not activate the base. How long does it usually take to get the base/clear "full adhesion" usually?

I'm going to experiment with the SPI epoxy, the main goal will be to get it to lay as smooth as possible, with maximum amount of build.

Because I am doing these in bulk, not having to sand the epoxy primer is my main production benefit. Just a denib then basecoat/clearcoat.

If I spray 2-3 coats of epoxy with 30% reducer so it lays smooth, how long of a window do I have so that I can denib, then base/clear?

I'm reading that reducer accelerates the epoxy, and some are saying 24 hours is the max before you need to sand the epoxy?

 

[dhutton01]

Pretty sure the tech sheet says only one coat of reduced epoxy as a sealer. Not 2-3 coats. Also says to activate the base....

Don

 

[ebaypdllc]

Yes, read tech sheet but its slightly confusing?

To use as a Paint Sealer: To use the epoxy as a paint sealer, reduce it 5-50% with the proper temperature range urethane reducer (this is very important) and spray with your base/clear gun. Spray one wet coat ONLY, let it sit 2 hours then apply paint. For sealing of a potential problem paint job, apply two coats of epoxy with proper flash times between coats and let it sit over night before painting. Remember, reducing epoxy speeds up the cure time, so when mixed as a sealer the best application of base is within 2-18 hours (no sanding is needed within this time frame).

So if I spray (2) coats, it says to wait overnight which i'm assuming is 12 hours? If two coats are sprayed, how long before I can wetsand to denib. So looks like I have 18 hours max to get it basecoated?

 

[crashtech]

I would say that 18 hours is a very safe number, in cooler weather that is extended quite a bit. But I have to ask, why do you think you need so much epoxy? Maybe the SPI will build better and you can just spray 1 coat at 25%. If you are worried about open window, you can check with your base manufacturer to see if the base is sandable, with many sealer applications, we shoot one or two coats of base within the time window, then nib the base instead of the sealer.

 

['68 Coronet R/T]

I am wondering about sanding with 1500 grit before base coat.
Generally 600 is plenty but I don't know how fine you can go before base coat won't adhere properly. Just a thought!

 

[ebaypdllc]

Thanks for help I really appreciate you guys!

I'm painting these parts in "bulk". About 10 sets a day or so. I will be selling these parts both in primer, and prepainted to the customers color of choice. If the bodyshop gets the product, they are going to sand the parts and base/clear with their process. I want there to be enough primer build so they don't burn through into raw plastic. Or maybe that doesn't really matter and it the bodyshops problem to figure out as long as it looks nice in primer when they receive it in the mail?

Unfortunately the parts get micro pinholes in the raw plastic. I wetsand the raw plastic with 400 grit on an abralon pad on DA. Then I use a glaze putty and skim over the whole part to fill any micro pinholes. I was hoping the epoxy would create enough build to fill any spots where the putty was in the pinholes.

But my original plan was to get these parts prepped and in epoxy primer. Then if I get an order for primered part, simply ship the parts out. But if I get a specific color ordered, pull the part from inventory that has already been epoxied primed and simply denib and base/clear and ship within 2-3 days.

I have never used epoxy primer in past, just learning how to use it now. I'm used to using 2K high build primers and sanding them smooth, then base/clear, that process is not practical to do these in bulk.

I didn't know that reducing actually modified the window times. So now i'm just trying to figure out a time efficient way of painting these in bulk.

I think maybe if I epoxy the parts in the morning, then base/clear at night time I should be okay?

 

[dhutton01]

Only one coat of reduced epoxy if you are going to apply base the same day as I understand it. If you need more coats apply them without reducer and let it sit 24 hours minimum before applying reduced epoxy as a sealer. At least this is the way I interpret it.

Activate your base so it cross links with the clear.

Don

 

[Jorge M.]

Pulling a part from inventory that's been sitting on epoxy for days or maybe weeks at a time, then doing a quick denib-base-clear may not give you the best color adhesion.

I would at least denib-scuff the 'old' epoxy, reseal with epoxy mixed 1:1:1 and spray activated basecoat. That way you'll know the basecoat is not coming off.

 

[ebaypdllc]

Agreed, I think im going to just epoxy prime parts in the morning, then base/clear at night to be safe.

Look forward to getting the SPI epoxy to test.

 

[Barry]

Answers have been good here but one thing I want to throw out is next day you will not have full adhesion with a base or clear as adhesion is gained as the product cure.
If you do break a spot one thing I always tell the guy when he calls is let that spot set over night and see if it harder the next day to peel back, reason, when you break a spot the solvents in that area, will rush out and you will gain bonding.