Blackdog36

iTrader: (3)

I am repainting my engine bay. Had to sand everything down with 80 grit paper to get rid off botched first attempt. I tacked cloth and wiped down everything. Then I sprayed a coat of Nason Full Epoxy with a coat of Nason sandable primer. I am smoothing the primer out with 220 grit sandpaper. I have broken through metal so I will need to spray epoxy again.

Does epoxy need a certain roughness to adhere better? I could go over the primer one more time with 400 grit before I spray epoxy to smooth things even more. If I do, is this too fine of a grit? I am hoping that the 220 grit will be enough and that when I spray the epoxy again, it will flow out and cover any sanding marks. I might try this on a little spot and see how it looks. Any thoughts?

MYFIRSTZ

220 will do nicely

camarotucker

iTrader: (2)

Spot prime bare metal only with Epoxy. Wait your flash time and spray entire panel with high build primer.

You made it sound as if you intend to fill the sand scratches with Epoxy. If so, Epoxy will shrink and not give you the intended fill. Additionally, if applied to thick (Epoxy) it will pop loose in the jams (corners).

I have worked panels with 80 grit, applied a high build, then 400 grit and straight to paint.

Blackdog36

iTrader: (3)

Thanks for the replies. Besides getting real tired of sanding, it is difficult to sand the engine bay and not keep getting down to metal in certain spots. The engine bay does not have many flat surfaces and even some of those have high/low spots along with metal tabs sticking out.

I was thinking that by knocking down the primer with 220 grit that the surface would now be smooth enough that if I sprayed epoxy, it would give me a smooth coat that I could then paint with basecoat/clearcoat.

If I spray epoxy only on exposed metal spots (which are numerous) and then spray another coat of primer, I could sand that down a little bit with 400 grit. I am concerned that I would still be exposing metal at that point. If I do expose metal, do I finish sanding with 400 grit and spot spray epoxy on metal? Then I could spray sealer and go to basecoat/clearcoat?

camarotucker

iTrader: (2)

Correct, as long as when you hit metal, you stop sanding.

MYFIRSTZ

Wow, I used nothing but epoxy primer on my whole car (3 coats block with 320), (3 more coats block with 600), guess its all gonna shrink up and pop off!!

Blackdog36

iTrader: (3)

I've posted a few pictures where you can see that I reached metal in many places. Even if I spot spray epoxy just over exposed metal, I will have sprayed a decent amount of engine bay with epoxy. I was looking to spray two medium coats with proper flash time as the tech sheet says. I got the engine pretty smooth after sanding a lot with 220 grit. Think I will spray epoxy on a little portion of the frame rail and see how smooth it comes out.

mille_3

iTrader: (3)

You're fine. As long as prep was done correctly and you paid attention to recoat times, you have nothing to worry about.

roadthrills

You can thin that epoxy primer out and it will lay out real smooth. I do that to seal up my work sometimes.

camarotucker

iTrader: (2)

Most failers of Epoxy are because of failer to follow flash times. Epoxy contains acid and if not flashed off enough will cause it to "pop" of the surface usually in jams (corners). Additionally, if applied to thick, it will shrink and pull itself away from the jams.

Epoxy is generally "non sanding", shrinks more than a fill primer and is also more expensive than fill primer. It has less mil. build up than Fill Primer. This is why it is not recomended for blocking.

camarotucker

iTrader: (2)

Looks like you are doing fine, I burn through on a daily basis way more than that. Dont worry about blocking the frame rails as they will not be visable after assembly.

camarotucker

iTrader: (2)

It should be noted that Epoxy is a darker gray than Sealer (gray). When Epoxy is used in place of sealer it will effect color match.

MYFIRSTZ

Ok, thats good info. I put mine on nice wet coats, but I was very good about letting it flash properly before the next coat.

Did not know epoxy had acid in it, I thought that was just etch primer...

I dont know about non-sanding, the epoxy Im using blocks great after about 2-3 days

YOU SURE YOURE NOT TALKING ABOUT ETCH PRIMER????

camarotucker

iTrader: (2)

Generally, Epoxy only requires a single coat. Epoxy, Etch, Wash, DTM, primers all contain acid, with Epoxy containing the least amount. Years ago Epoxy was the coating applied to new parts and was replaced by what is now known as "E-coat".

There are some "sandable" Epoxies on the market today, but you have to order it specifically as a sandable formula. I have yet to use a "sandable" Epoxy but I am looking to try some out when my current supply runs out. I dont know first hand, but if I had to guess, the sandable Epoxy will be more expensive than "non sanding".

roadthrills

I should have been more clear. I mean just to seal up while in the first stages. I don't like paint right over epoxy. When everything is done I use a high build then final blocking

Blackdog36

iTrader: (3)

Thanks for keeping the conversation going.

I've had some time to think about it and try a few things. I think a big cause of my initial paint problems was that the primer/paint was spraying to gloppy and not a fine mist like it should be. I have a DeVilBiss Plus spray gun that requires 9-11 scfm per manufacturer. My air tank is 30 gallons and can supply 8.8 scfm at 40 psi. If I put my tank pressure gauge down to around 35psi, I get 30psi at my gun regulator. 30psi is the lower range of the paint products I'm using. With my gun and tank, I think that I can just make it work on the low end of requirements. Wondering if I can also use one tip size smaller then recommended to keep up the pressure.

I finally finished sanding the engine bay with 220 grit sandpaper last Sunday. Next I tried spraying epoxy primer on a few portions of the driver side frame rail and firewall. The epoxy sprayed a lot better but was still a little to gloppy for my tastes but not sure if it supposed to be like that. Attached are some before and after pictures of these areas. The epoxy will still need to be sanded lightly to smooth it out unless I spray more primer on it and sand with 400 grit. Here is my plan. Tack and wipe stages are included.

1) spray epoxy on exposed metal spots.
2) spray epoxy over outside of frame rails, front bumper area and inside of radiator support. Mask off these areas from primer in next step.
3) spray two light-medium coats of primer on inside of engine bay, firewall (including top) and top portion of front bumper cross member. These areas will be visible when finished.
4) sand primer with 400 grit as recommended by tech sheet. sand epoxy areas with 400 also to roughen then up.
5) spray black sealer on everything (already have some so will use it).
6) follow up with basecoat on everything.
7) finish with clearcoat on everything.

Blackdog36

iTrader: (3)

A few more after photos.

Blackdog36

iTrader: (3)

Well I finally have an update but not the one I was expecting. Although less then my first time, I have major orange peel again. More on this later down. Not feeling to happy at this moment since I have been working on this engine bay for the last two months straight. Even spent most of my holidays and a few vacation days working on it.

Regarding my outlines steps above, I did steps 1-3. Thankfully the epoxy and primer took less time to sand than before (still a while thought). I had some bare metal spots so I sprayed a coat of epoxy on these areas (step 4). It was basically most of the engine bay except the radiator area as that was still masked off. Sanding this last coat went quick but I still burned through to metal in many areas. After looking around online and calling my paint shop, I confirmed that you can use sealer to cover small metal spots (less than a quarter). I re-taped my car and prepped it for spraying with Nason 2k black sealer. It sprayed nice although I think it could have went on smoother. Here are two up close pics on the front frame rail corner. Does it look correct and smooth enough?

Blackdog36

iTrader: (3)

Here are three pictures after basecoat and clearcoat. I used Dupont Chromabase 9900S Super Jet Black which looks great. A deep dark black. The last picture shows how bad the orange peel is. Looks really crummy since I am up close with a camera flash. This time the paint was spraying a good fan pattern but it seemed that the paint was still spraying big droplets. While spraying one part of the frame rail, I could see a couple large drops bounce off the top frame rail and fall over onto the battery tray area.

I read about orange peel and not sure what my problem exactly is. I used correct sized gun tip and I also believe pressure per tech sheet. Although my compressor should be good enough, I think it still can't supply enough volume (maybe 1-2 scfm short). My compressor is 30 gallons and can supply 8.8 scfm at 40 psi. My DeVilbiss Plus tech sheet says it needs 9-11 scfm. My thinking is that if I have my tank at 35-40 psi this gives me 30-35 psi at the gun which should just be on the lower end of the gun requirements. The paint tech sheets give you pressure ranges for gravity guns usually with range of 30-40 psi but 8-10 psi at cap for HVLP guns. Frustrating...

Not sure what I am going to do yet but definitely taking some time off from the engine bay and working on something else. Maybe I can keep it like this and have it as a textured look

I'm pretty sure that I am not going to sand it back down and start over. I am mentally and physically done with that part after doing it twice already.

I could wet sand and buff the main areas that would be visible once everything is reassembled. I might try this on a small area of the outside frame rail to see how much time would be involved and what the finished product would be. I know that I won't be able to a full and correct wet sand/polish job like you could on a flat body panel but maybe a little wet sand/polish by hand will improve things a lot. Thoughts?

Yenipenny

Based on what you've said in the above post and others, the pressure at the gun is way too low and/or the material hasn't been reduced properly. That's about the only way you can get orange peel that bad.

You will never be able to wet sand and polish all that orange peel off. You'll need to bite the bullet and sand it down with 400 grit and re-spray. Practice with different gun settings on some scrap metal 'til you find the correct settings. It takes considerable experience to set up a gun without some practice/experimenting. The recommended "book" setting are just a guide.

Blackdog36

iTrader: (3)

Thanks for the response. When I sprayed the epoxy, I bumped up the pressure and it seemed to spray better although not smooth enough for how I think it should be. I still believe that my compressor can't supply enough volume.

Although it will be a lot of work, I know that I won't be satisfied with how it currently looks. I will have to sand it back down over several weeks. Doing it slowly while working on other car projects will be easier than doing it weeks straight. I wonder how slow 400 grit will be. I used 80 before to knock it back down after my first botched attempt. That took a while! Will have to try a small section with 400 and see how that goes.

I will look into getting a better compressor and practice on a spare fender I have. Just very frustrating at this point, I feel like an idiot.

Yenipenny

For irregular surfaces like an engine compartment, I like to use a fine grit sanding sponge. The fine grit is about the equivilent of 400 grit or you can wrap a quarter sheet of what ever grit you want to use around the sponge and you still get the sponge feel. I think you'll find the sponge will be much, much faster. A multi-tool with the sander function can also speed up things.

Your compressor is a bit on the low side in terms of volume, but with the proper spraying technique and letting the compressor rest when the pressure starts to fall, you should be OK.

Blackdog36

iTrader: (3)

Yeni, thanks for the advice. Haven't tried sponge yet but forgot I have a Black and Decker sanding mouse. I've been using that the past few weekends and pretty much have my whole engine bay sanded down! Used 80 grit sanding pads and it ate right through the clear coat and paint. Don't know why I didn't think of using it before. It really helped since before it took so much sanding effort to remove clear coat and paint from my first failed attempt.

I need to get some better 120 grit sandpaper. The stuff I have doesn't work the best. I bought rolls of 3m paper in other grits and that stuff works way better.

When I rewired my garage, I ran two 12-2 lines. One I had just a dedicated outlet for my compressor. I can upgrade that line to a 20amp, 240 volt socket. I'm going to buy a Kobalt, 60 gallon single stage air compressor at lowes next weekend. It puts out 13.4 psi at 40 psi. I think that will make my gun work like it is supposed to.

I just have some spot sanding left to do by hand and then I will be ready. Might try out new compressor and gun by painting a spare fender with sealer, base and then clear coat. My engine bay is pretty smooth from the orbital sander so I may just use epoxy primer and skip the sandable primer. I plan on having bay painted by end of month. Hopefully will have some good news and pics to report back with.