Using Epoxy Primer in an Unconventional Way

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PostPosted: Sat Aug 06, 2022 10:18 am
Hello,

To get straight to the point, I have been focused on getting a chrome-like finish on plastic for around 2 years now. Eventually, I came to the conclusion that I was going to have to get into using automotive paint for durability and to get a good mirror-like finish prior to spray chroming process.

So, maybe a year or so ago, I reached out to Speedokote and told the rep what I was trying to do. He recommended a clear (necessary after the spray chrome process to protect and prevent from yellowing), and a single stage black to get a good dark smooth surface.

Now, for some reason, he recommended epoxy primer. Maybe this would be good if the surface was smoothed to an ideal level, but I believe this to not be realistic for what I am working with (Xbox Console). I have previously tried sanding the textured plastic surface smooth with disastrous results. To get it smooth, I ended up taking out too much of the intricate details, as well as the problem of the sandpaper getting clogged easily. I think he may have suggested epoxy primer since different parts of the Xbox are made out of different types of plastic. He ASSURED me that this stuff will bond well to plastic and will not require any adhesion promoter. I have not found anybody else online supporting this claim. I kind of think he was just trying to push a product on me that might not sell as well...

A little backstory. The biggest issue I had while trying to learn how to spray was simply not getting the correct volume of air to my gun. The biggest thing that changed this was changing my quick disconnects to high flow. When I was first spraying the epoxy with incorrect air volume, the gun kind of spit out these chunks. Also, since the paint wasn't getting atomized properly, it was coming out too thick.

So, not knowing any better at the time, I thought that was how it was supposed to come out and I just smoothed this down prior to single stage. Of course, since it was on too thick, I started getting these very tiny bubbles within 10 minutes of spraying the single stage. Now that I have correct air volume, this isn't happening anymore.

Now the epoxy goes down very thin. It doesn't really cover up surface imperfections with 2 coats. After hours and hours of online research, I am convinced the PROPER way to do this would be to completely ditch the epoxy primer, and instead spray adhesion promoter, and then high build. Blocking that down prior to single stage.

However, I can't stop thinking about how smoothly the epoxy primer leveled out (when spraying incorrectly) and covered up everything. I can't help but wonder what the results would be if I got my epoxy primer to that same thickness, but instead used multiple thin coats to build it up, allowing proper flash time between coats.

Basically, I'm thinking about trying to use epoxy primer as one might use a high build. The surface is so smooth, that I think I could practically spray on top of this with minimal, if any sanding. That would be great because it takes me hours with a red scuff pad to get the plastic prepped on just one of these.

I am aware this is not correct and I will most likely need to go out and purchase some high build instead. I am just curious to know of what kind of potential problems I may run into doing this. Since this is a video game console, it will always be indoors, at room temperature. It won't be exposed to the elements or sunlight, and will always be stationary. Considering these things, some of the concerns when working with something like a plastic bumper cover will not apply to this.

I guess I won't really know until I try this as far as immediate issues go. I am posting this to understand more about what the possible long-term effects may be (assuming I am able to lay down the single stage without solvent pop or anything).



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PostPosted: Sun Aug 07, 2022 6:58 am
You CAN buy some epoxy primers that are high build. But they are not going to spray as nicely as re epoxy made for adhesion/sealing. House of Kolor is one, EP-2, and Tamco makes one as well, slow cure time, though.

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PostPosted: Sun Aug 07, 2022 10:27 am
The solution, in this case, is just the same as it is with every other refinishing job.

Get your substrate right and you won't have to rely on paint to correct failings underneath.

So, get your plastic smooth and then 2 light coats of epoxy. It's just a bond between the topcoat and the plastic, and yes, it will stick to the plastic. Don't use other things like adhesion promoter or etch primers under epoxy.

You can spray topcoat over the epoxy after a short period (check your TDS), often 20-30 minutes, or you can let it cure longer and give it a very light sanding to remove any nibs. If you've put it on right there should be almost no peel.
Chris



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PostPosted: Sun Aug 07, 2022 11:00 am
chopolds wrote:You CAN buy some epoxy primers that are high build. But they are not going to spray as nicely as re epoxy made for adhesion/sealing. House of Kolor is one, EP-2, and Tamco makes one as well, slow cure time, though.


Interesting. Looks like I have some experimenting to do. I am using SMR-260B as my epoxy primer. My last spray with this was reduced. I am going to try again unreduced and see how many coats that will take to build up before trying a product like this. I suspect that what I am using is not much different than some of these. The slow cure time doesn't bother me.



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PostPosted: Sun Aug 07, 2022 11:28 am
NFT5 wrote:The solution, in this case, is just the same as it is with every other refinishing job.

Get your substrate right and you won't have to rely on paint to correct failings underneath.

So, get your plastic smooth and then 2 light coats of epoxy. It's just a bond between the topcoat and the plastic, and yes, it will stick to the plastic. Don't use other things like adhesion promoter or etch primers under epoxy.

You can spray topcoat over the epoxy after a short period (check your TDS), often 20-30 minutes, or you can let it cure longer and give it a very light sanding to remove any nibs. If you've put it on right there should be almost no peel.


I understand the importance of getting the substrate properly smooth. Trust me, I tried. I really have no good idea of how to get this sanded down to where it should be. First, it is very difficult to even get the larger flat textured parts smoothed down. I absolutely could not do it by hand. I had to take a dual action to it while keeping the surface wet to prevent the pads from gumming up. This took considerable effort.

I found the sharper edges almost impossible to do without rounding them off. Then, the biggest problem of all is some of these intricate areas. Dual action is not an option for smaller parts. Using a Dremel caused problems too, usually taking too much off in some areas. I am going to try to attach a photo below of probably the best example.

The disc drive cover is a very small part. It is like, 1/2" wide piece. As you can see, there is some raised lettering. The tops of the letters are easy, but the black plastic it is raised out of that is textured is very difficult. Maybe there is some kind of specialty tool I can use to hit just the textured stuff, but it is very difficult to work with without sanding too much off of the actual letters. With my first attempt, I ended up just sanding the letters completely off. Luckily I have more. I really don't want to do something like that. What I can do is get all of this scuffed with the red scuff pads.

Thank you for confirming that adhesion promoter is not necessary with this. I have some conflicting information regarding this product on their website. The description states that it can be top coated after 30 minutes per coat, or up to 3 days. After 3 days it must be sanded as it will no longer provide a chemical bond, and would then require a physical bond.

But then the TDS states 30-60 minutes before topcoat (I'm guessing depending on how many coats you use) and that it must be scuffed and recoated if left to sit for more than 24 hours. I was planning on the epoxy primer being the only thing I do one one day, and then come back the next day for topcoat.

Image

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PostPosted: Sun Aug 07, 2022 2:12 pm
24 hrs?
The epoxy primers I use have up to a 7 day recoat window.
I've never seen such a short recoat window as yours for epoxy,
24 hrs is ridiculous.
JC.

(It's not custom painting-it's custom sanding)

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PostPosted: Mon Aug 08, 2022 9:27 am
did you ever say what spray chrome system you are using ?
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PostPosted: Fri Aug 12, 2022 4:00 pm
PainterDave wrote:did you ever say what spray chrome system you are using ?

Pchrome



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PostPosted: Fri Aug 12, 2022 4:04 pm
Ok, this isn't going to work. I'm ditching the epoxy primer. I guess I could try high build epoxy, but I don't really see the point. I plan on going the adhesion promoter / high build route. Any ideas of how I can possibly sand around the letters in the picture I attached? I would need something with a very small tip. I don't trust myself hitting it with a dremel tool.

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PostPosted: Mon Aug 15, 2022 12:42 am
Epoxy is not working so you want a high build epoxy ? that dont make sense.

I dabble a little in spray chrome.

give me a quick detail on process ?

this is for your xbox piece ?
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