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View Full Version : etching primer over epoxy ?? SCAMP



headonz
07-16-2015, 12:28 AM
If I use spirit based etching primer ,do I have to sand the last interior coat of epoxy or will the etching primer bond well enough providing and blush is removed ?

Its just that I decided to add a third coat of epoxy after assembly.


thanks

Lindsay

Scamp
#326

Todd Bradshaw
07-16-2015, 12:58 AM
In my opinion, spirit-based anything is often far more likely to contaminate the surface and cause problems than help. Yes, you want to get rid of any blush (or anything else that may have settled on the surface) and plain water and a Scotchbrite pad will do that and is a good idea on any epoxy, blushing or not, but assuming that the epoxy will be "cleaner" after going at it with solvents can very often be a mistake.

jgmarine
07-16-2015, 06:11 AM
Hi Linsay
West system 207 hardener has no blush, only the 205/ 206/ 209 hardeners

wizbang 13
07-16-2015, 06:15 AM
don't fix what ain't broke

headonz
07-16-2015, 03:55 PM
Ok,I am even more confused ,

There is blush ,I have been removing it with water and paper towels ect .

Should I use water based etching primer ?

Do I even need to paint the epoxy , being interior under seat and for peak lockers ect ?

Todd Bradshaw
07-16-2015, 08:54 PM
Epoxy resin that has been sanded smooth is probably the best, most moisture resistant and toughest "primer" you will ever find. You paint over epoxy for two basic reasons: (1) to protect it from UV, which will deteriorate it, and (2) to make it look nice. If it doesn't need either of those due to location you don't have to put anything over it if you don't want to. The function of most of the high-solid primer/undercoaters is to give you something that fills tiny defects, sands easily and in some cases evens out the base color you intend to paint over, if needed (often not, but depends on the paint used). There is no "etching" needed on a sanded surface, and the reason we sand the resin is mostly because it doesn't go on as smoothly as paint and looks a lot more professional when it is smooth.

suzyj
07-16-2015, 09:46 PM
What Todd said. Epoxy is an excellent substrate for topcoat. It's only downside is that it isn't as easy to sand as undercoat. Primers are more used to promote paint adhesion on metals, by etching the surface to provide a mechanical key for the paint.

paul oman
07-17-2015, 04:58 AM
the long cure (over a week) for epoxy allows chemical bonding (in addition to normal mechanical bonding) of coatings applied over it -- a good thing! Thus in the bonding area, epoxies can be the ideal primer

paul oman
progressive epoxy polymers

Dave B
07-17-2015, 10:09 AM
I don't want to jump the original question, but isn't the issue about what to do in those areas that you need/want to paint, but it's next to impossible to adequately sand to get rid of the epoxy glossy surface and provide tooth for the paint?

I know that I've got one of those situations coming up soon and it would be great if I could simply wash off the blush and paint with something that would adhere to the glossy epoxy.


Sent from my iPhone using Tapatalk

Todd Bradshaw
07-17-2015, 10:53 AM
If you wash the blush off, most paint will stick pretty well to unsanded epoxy, just not as well as to the sanded version. If it is an area that you can't get to easily, it is unlikely that it will get much foot traffic or other wear and tear and it will probably be just fine. Rolling and tipping thin coats of resin is usually the easiest way to coat these areas and end up with a reasonably smooth finish, assuming that you can get in there to do it. Drips and runs are caused by applying too much at once and having uneven thickness in your resin coats, so the more evenly and thinly you apply it, the better.

headonz
07-17-2015, 05:35 PM
Thanks guys ,good info Todd ,I hear what you are saying but Dave B has hit the nail on the head.I cant get at the area to do a proper sanding job so wondered if itching primer would be help here.But doesnt sound like normal practice.

I dont care much for the look of epoxy over plywood and really only visible when I open a hatch so I guess not essential that I paint it at all.

I will give it a few days to rattle my brain before I decide what to do ,mean while I have a centerboard accidentally glued in place while setting up the stainless bolt and bronze pivot yesterday ,to get out . A larger hammer may be required .

epoxyboy
07-19-2015, 02:32 AM
Hi Lindsay, +1 on what the others have said about getting rid of blush.
As for a priming coat over epoxy, I can recommend the "Smooth Surface Sealer" from Resene - and you know you'll be able to get it because its a Kiwi company!
I used it on my Pathfinder build, and have to say that to begin with I was pretty dubious about it, as it's waterbased, and looks like *very* watered down primer.
It is the opposite of "high build", so it wont hide any imperfections, but it rolls on super easy, a little goes a long way, and boy does it stick like $hit to a blanket to epoxy, leaving a very hard slightly matt finish for whatever you use as primer.
It is actually designed as a primer for painting stuff like Formica or ceramic tiles.

Pete