Spraying engine bay and chassis with Epoxy Primer only

ATXbronco

Promoted Users
Hey folks, new painter here with a rust-free 90's Bronco (some very light surface-rust), a gallon of SPI Epoxy black and a gallon of SPI activator.

I was hoping for any last minute tips/advice anyone can share with me?

I've got my front clip removed and am almost ready to paint my engine bay, front chassis, steering linkage, driveshaft, etc.

The existing engine-bay paint is factory original and in decent shape. I'm changing the color from green to black.

I'll be spraying (for the first time ever) and have a 1.4 and a 1.8 tip for my DeVilbiss FLG5 HVLP gun and 5HP/80Gal compressor.
I have a 3M half-mask with new organic cartridge and dust filter.

I'm in Central Texas and temps are forecast for a low of 60F and a high of 75F.
I'll be out in my driveway when I spray.

Here's my plan.
I'm writing it down for me to follow and you to critique.

1) Pressure wash everything REALLY WELL.
2) Sandblast engine-bay area of chassis.
3) Pressure wash everything.
4) Sand engine bay firewall with 180 followed by 220 then 320 (I have a 3" DA and a pad). And use a maroon 3M scuff pad in corners/hard to reach areas.
5) Pressure wash everything.
6) Degrease everything
7) Let everything dry 100%, using sun + leaf blower + air blow gun + propane torch (if needed).
8) Wait till it's 70F and then Spray everything with three medium coats with 20 minutes in-between.
9) Touch nothing for a few days.

The left/right fender and the front radiator support are in my back yard laying against the fence. I don't really have a plan for them yet.
I'll also be painting all the little under-chassis bits like tie-rod ends, linkage, etc., in my open garage.
For some of those, I also want to add a top-coat of various colored VHT Engine Enamel.
 
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The recommended grit on metal for SPI is 80 grit, so all that 180 220 and scotchbrite is not what is recommended.

The gray area I always never understood was spraying over old paint. There are primers that say it is OK to use that way, I am sure SPI would stick to it, but the job starts at the initial bond of whatever is on the metal to the first coat, so if its paint, its not really following the bible.

If you are blasting, why so much power washing unless you are reusing the sand. Blast, wash with dawn, wipe with wax and grease remover and spray are the basic steps.
 

RosharonRooster

Promoted Users
Do u plan on rebuilding the suspension and chassis? If not. Thats of work for some worn out parts. If so spraying epoxy is the easiest part.
 

ATXbronco

Promoted Users
80Grit and nothing smoother? Not even for the engine bay?

Yep, I'm repacing tie rods, ball joints, etc. etc. And replacing engine. And maybe even install a lift kit.
 

ATXbronco

Promoted Users
Would this count as Soda blasting or Media blasting?
Page 13 of the tech manual advises a different process for the two.

Summit Racing® Silica and Slag Blasting Media​

Blasting Media, Slag, 20-40 Mesh
 

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MP&C

Member
Personally I would move the degreasing part higher on your list, before sanding. If you have grease and other impurities on there, no sense in sanding/scuffing over them and dragging them deeper into scratches...

What you're showing would be media blasting. Although what's in the picture looks entirely too coarse for sheet metal. Soda is Baking soda, and changes the PH of the panel, or decreases adhesion qualities. I prefer a silica free garnet media personally, and stay away from "sand" as they typically contain caustic salts. Not something you want pounded into sheet metal..
 
Would this count as Soda blasting or Media blasting?
Page 13 of the tech manual advises a different process for the two.

Summit Racing® Silica and Slag Blasting Media​

Blasting Media, Slag, 20-40 Mesh
you can get this same stuff at Menards home centers for about 8 bucks a 50 pound bag. If you have a blasting supplier, they call it black diamond, usually about 20 bucks for an 60-80 pound bag. Available in 12-20, 20-40 and finer. It cuts much faster than aluminum oxide or garnet, I use it for sheet metal as long as you stay far apart and dont throw 170 pounds of pressure. Most suggest 90 tops and I highly doubt that compressor will stay at 90 for long, it will probably drop to 60 where you wont hurt sheet metal.

The bigger reason people like garnet is not dealing with the silica health issues. It pushes more towards aluminum oxide, plus, if you buy garnet paper its pretty much made for wood. The more common media is crushed glass, people like it because it explodes on impact, (like baking soda) but sounds like silica to me. Its been fast, but I just used it in a blasting cabinet and it just turns to dust too fast.

I would blast as much as you can. Just saying if you are blasting the grease will go as well, but if you want to try to reuse media, then do all the degreasing so you are not pounding it back on. Blast the frame, blast the hard to sand areas, inside corners, enough to where you can clean the hard stuff. Then stiff wire brushes or DA the flatter sheet metal parts, you can start with 36 and finish with 80.

Blasting is just ready for epoxy.
 

Chris_Hamilton

Trying to be the best me, I can be
You can get coal slag (Black Diamond brand) at Tractor Supply for about 10 bucks per 50 lb. bag. Shipping is so high you need to buy it in person. If you can get crushed glass media where you are it is also about 10 bucks for 50 lbs. Northern Tool did sell it but I haven't been able to get it there for a while. Look for grit range of 40-60 (medium). 20-40 is going to be too harsh. If you are doing an entire vehicle something like that Bronco you would need at least 500 pounds IMO.
Also being you are new to this I would think twice about blasting exterior sheet metal. Pretty easy to screw up and warp sheet metal media blasting. Better to sand strip the exterior metal and save the blasting for the engine compartment, underside/inside and frame and components. If you do, use low pressure like AI described (60 psi max) low amount of material and keep the blast gun a good distance away from the panel. Contrary to what gets repeated on the Internet it's not heat that warps the metal its air pressure and material volume.
 

ATXbronco

Promoted Users
Thank you all.

Good tip on moving the degreaser to an earlier step. To prevent grease from going deeper into the frame/scratches and also to allow the media to stay "clean" so it can be re-used.

I had only planned on blasting the frame but maybe I should consider blasting other parts as well. But maybe not the exterior since I'm inexperienced and don't want to screw up the exterior. I probably don't have enough media for that either.
 
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ATXbronco

Promoted Users
I had hoped to paint tomorrow (Saturday) but I'm not yet done stripping the front clip of my truck.
I'll need all day Saturday to finish removing things and then start cleaning/sanding.

I won't be able to paint until Sunday when the temps range from 78F to 50F overnight (I work Monday).

After I paint I should have about eight hours before it hits 65F.
10 hours before it hits 60F.
12 before it hits 55F.
And about 19 hours till it hits 50F outside, then it starts warming up to 78F a few hours after that.

Will the Expoxy be okay with that?
I'll put the car-cover on it over it overnight, which should keep the wind-chill away.
 

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ATXbronco

Promoted Users
No it will not. Please read and follow the tech sheet. 65 degrees minimum for 24 hours.

Don
Okay thanks, I'll push it out till Thanksgiving day which is projected to be a low of 64F.

I did read the tech sheet. The frame itself needs to be 65F or warmer for 24 hours.
Had hoped someone would suggest that maybe the very brief/temporary dip down to 50F might not be long enough to matter if my truck was covered up.

I need to cross my fingers these aren't the last 60+F overnight temps for the next few months.
It's Central Texas, so we'll probably have several more (I hope).
 
The tech sheet should be followed as Don has pointed out, however 50 degrees was the original temperature given before the epoxy would stop curing.
Are you painting outside?
It is best to leave the car indoors and put a small heater in the room to keep temperatures close to 70 overnight.

I would not cover the car until epoxy is fully cured.
 

ATXbronco

Promoted Users
The tech sheet should be followed as Don has pointed out, however 50 degrees was the original temperature given before the epoxy would stop curing.
Are you painting outside?
It is best to leave the car indoors and put a small heater in the room to keep temperatures close to 70 overnight.

I would not cover the car until epoxy is fully cured.

I'm painting the part of the engine bay you see in this picture, and painting the frame, outside on my driveway.
It's all being done outside on my driveway and after the sun goes down, I'll bring the car cover over to protect from overnight dew.
The cover won't touch anything other than the very front tip of the frame and will be secured from flapping around in any wind.

Will be painting the other fenders/core support and bits inside my garage.
There isn't any room to bring the truck into the garage.

Going from green to black.
You can see where the previous owner started painting black and then gave up.
 

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There are industrial epoxies out there they use on fueling machines and outside structures that cures at or just below 50 degrees, this is not one of them. Electric heat, kerosene heaters are pretty cheap out there to heat up the frame until it gets warm before you push it outside to spray, then right back in when you are done. If you are going to do that, I would think metal temp starting at 75 would keep it above 65 thru the curing. Unless you are using infrared, which works by heating metal, not air, it might be in the garage til thanksgiving to get there.
 

ATXbronco

Promoted Users
It's 11:45AM here in Central Texas and I just pulled the car cover off my truck.
Grabbed my laser thermometer gun and started checking things.

Outside, it's 75F. The driveway itself is 74F.
But the frame and firewall part of the engine bay are both six degrees warmer at 80F.

I'll check it earlier tomorrow morning, like 8AM. See what it's looking like overnight.
 
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