Questions regard epoxy primer and steps following.

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PostPosted: Wed Jan 26, 2022 11:14 am
Hi everyone this is my first post here and my first time doing anything autobody related. so thanks in advance for anytime taken to answer my questions. I've been reading a ton trying to find the answers but there's so many different products and opinions that it is becoming overwhelming to say the least.

So anyway I'm dong front fenders, inner/outer rockers, cab corners, and other rust repair on a 2006 Silverado. after stripping everything to bare metal, cutting/ grinding rust I've decided i want to use a a 2k epoxy primer (transtar 6134 from local paint shop) I have a few questions regarding the best way to proceed after applying my first coat. So I plan on coating all the new panels before welding them on so I can get the backsides sealed.

My first question on this: What is the least expensive option for painting the insides of the rockers and fenders that wont show, Or is this whole step unnecessary and can I get away with just using cavity wax on the inside?

Second question: I've striped the factory E-coat on undercarriage to bare metal because there was some bubbling starting in spots and I want to cover that as well with Epoxy and some type of hard paint or clear coat that will resist chipping (I do not want to use any type of bedliner/ rubberized coating on this) What kind of paint/clear is recommended and is there a generic gray or cheaper black paint I can use on the undercarriage and inside the Fenders instead of the expensive color matched stuff I plan on using for the final paint job on exterior panels. Or would Primer with bedliner followed by a sealer be the best way to do this?

Third question: Is primer surfacer required for paint to adhere, or is that just so you're able to sand and blend the filler with existing paint? I'm asking because it recommends it on the product date sheet but if I can skip this step on the undercarriage and just prime/seal/paint it would save me alot of time and effort because I'm working off jack stands.

Forth question: What are my options on paint? Is acrylic urethane the only way to go? The guys at the paint store seem knowledgeable but they also are good salesman and seem to be trying push stuff on me because they know I'm clueless. Two part question: what is the best type of Clear coat I should use on the final paint job?

I know this is alot to ask so i hope I've outlined in a way that's easy to read and understand, I appreciate any advice because all this is terrifying to me and I have so much time and money into this project already and I just want to do it right. It's a work truck but I want it to last and future rust prevention is my main objective.
Last edited by 06duramax on Thu Jan 27, 2022 10:21 am, edited 3 times in total.

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PostPosted: Wed Jan 26, 2022 11:02 pm
So I got down to your final question there and my though processes on the other questions just stopped cold (sorry, long day). You have got to get a handle on this cold shop thing before you waste a lot of expensive paint which might never dry. Personally, I don't like to paint anything at less than 65 F and I feel a lot better at shooting at 70+. Cold only slows down your whole process with off gassing. EVERYTHING in the room should be those temp.s too. That means the metal, the paint, etc. You can have a farily warm room but the metal may not be at that temp. Okay, so here is another problem.... CATALYZATION.... All epoxies use a hardener process which is a chemical reaction that must start/end. Drop below 55 with most of them and the process just won't "kick off" and start. You can even have your epoxy warmed up but if it hits cool metal it's over. You'd have a big gloppy mess to scrape off. Polyurethanes aren't much different, they will all have hardeners as well. So the rest of guys can answer your other questions easily..... but, it you can't get past this cold shop problem you've got much worse gremlins than all of that in your future.....
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PostPosted: Thu Jan 27, 2022 9:43 am
My plan if that is going to be an issue is to hang plastic sheeting around the truck and use a kerosene heater to warm that space, it's a big open garage about 50' long with 20' ceilings and stone wall, and oil burning furnace so heating it is super inefficient and exspensive, I turn it down to 40 overnight and keep it at 50 while i'm working to conserve heating oil and i've already burned through almost 150 gallons since starting this project in November.
My buddy knows a guy that might let me use his paint booth to do the replacement panels. But Thanks for confirming that before I wasted more time and money!

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PostPosted: Thu Jan 27, 2022 12:01 pm
You will need to get a good Infared thermometer and verify your metal temperature.
Booth temps may feel warm but it takes time for the metal to get to the correct temperature.

Something like this: https://www.thermoworks.com/ir-gun/?utm ... um=organic

I use an Electric Heater in the booth area and get everything up to 70 degrees. Paint, reducer, primer, etc.

Turn the heater off while you spray and then as soon as the over spray cloud is gone, turn it back on. These heaters operation via a coil so there is no spark or flame to be overly concerned with.

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PostPosted: Thu Jan 27, 2022 12:29 pm
Okay I have the heating situation figured out, I also have a infrared thermometer. But how long must the metal and primer stay at 70 degrees during the drying curing process after spraying?

Ive been reading a lot about epoxy primer/sealer and I think I understand most of the process for finishing the body from metal to clear coat. My only confusion is is if it is entirely necessary to use a primer surfacer, or can I just blend my body filler into the epoxy primer and seal it?

Will the finish on the fenders turn out bad if I don't use surfacer? I'm not to worried about the door jambs where the new rockers will be welded on but I do want the fenders to look half decent. So if a surfacer is absolutely necessary for a good end result, can use the stuff in a rattle can or is a 2k urethane the way to go?

Also still wondering what I should use on the undercarriage and insides of the rockers and fenders, I'd prefer something other than rubberized undercoating, all the cars I've owner that had it had major rust problems.

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PostPosted: Thu Jan 27, 2022 1:18 pm
The problem with using straight epoxy will be the temperature.
Epoxy will need to be kept at 70 degrees for 24 hours in order to cure enough to move on to your next step.

2 coats of epoxy on bare metal, keep it heated for 24 hours minimum, then you can do your filler work and feather it into the epoxy.

I would only use 2k products and not the cheap rattle can stuff. You will be asking for problems.

The 2k build primer will cure much faster than the epoxy primer so you won't be having to heat the garage as much. Read the tech sheet for the 2k and it will give you minimum flash times. 3 coats is what I start with and then let that cure at least over night, longer if possible.

Guide coat is your friend. I like the 3M Dry as it goes a long way and also gets into the smallest of scratches.

Block sand with 180 grit to remove the guide coat. This will remove a lot of your 2k build primer but the goal is to get the panel flat. If you still have guide coat showing and are starting to see epoxy primer in places, you may need to shoot another couple of coats and start the guide coat blocking process again.

Once you can remove the guide coat without hitting metal, you apply more guide coat and switch to 320 grit. Remove the guide coat and then I usually apply more guide coat and wet sand with 600 grit on a soft blocking pad.

When done you wipe it all down with automotive Wax and Grease remover (spray it on and wipe it off with a clean shop towel before it dries) and then let it flash off.

Booth and metal temps will need to be at least 70 degrees before the next steps which can all be done in one day.

From here you can go straight to your base coat or you can apply a sealer coat (optional). I usually go straight to base and shoot 3 coats using at 50% overlap. Again read your Technical Data Sheets for your products.

Once the base has flashed off the appropriate amount of time, you can shoot your clear coat. 3 coats minimum is my recommendation. You will want to shoot 4-5 coats if you plan to cut and buff, especially if this is your first time doing so.

Keep the both at 70 degrees overnight to allow the clear to cure. If possible get the vehicle in the sun a few days before you try to cut and buff. It will help the clear to cure.
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PostPosted: Thu Jan 27, 2022 1:37 pm
I use black epoxy on the under carriage. It will be fine on any parts not exposed to direct sunlight.

Dana 60.JPG

K-Frame in Epoxy.JPG


You an also get epoxy in a Red Oxide color.
SPI Red Oxide Epoxy.jpg
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PostPosted: Fri Jan 28, 2022 2:37 am
thanks for the detailed response, the black epoxy you use on the undercarriage, what type of product is that considered? And is that all you put on is epoxy or is there anything else that should be followed up with for a good hard surface? This truck will see alot of road salt and be parked outside so corrosion is my biggest concern, I filled half of a 30 gallon garbage can with rust flakes and dust when I cut out the old stuff on just the drivers side, the panels that were still intact had almost nothing left. And the tops of all 3 body mount brackets were gone I welded on new tops, replaced the floor pan, floor reinforcement channel under the seat. Unfortunately I have to go back and lacquer strip all the cheap rattle can primer I applied to the underbody already as well as a can of zero rust the paint store talked me into I haven't even started the passenger side due to space limitations, but i can see already it's not as bad so it should go much smoother with what I know now.



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PostPosted: Fri Jan 28, 2022 2:56 am
Also I'm not doubting your knowledge or experience but the TDS for the epoxy i'm using says it can be applied at 50 degrees it just has a 45 minute wet on wet recoat time instead of 30 minutes @ 70 degrees. Do you think ill be okay at a lower temperature? I'd love to have it warmer in there but it's not feasible to run the furnace that high for extended periods ill burn through rest of the heating oil in a day or two, my plan is to run kerosene turbo heaters to get the garage space up to temp and have one about 10 feet from the truck to warm the metal then get it as hot as possible in there before I paint and turn them back on for a few hours after it drys and keep the furnace set at 60 before leave for the night. i cant leave the kerosene heater running all night, though I could try and find an electric one id feel safer leaving it on.



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PostPosted: Sat Jan 29, 2022 8:35 am
Oh boy... The epoxy will eventually cure, even lower then 70, but you'll absolutely have to wait to coat it with anything, until it's totally cured.

The other major challenge you can't even see is the heating situation, your pumping what is basically jet exhaust into what should be a clean shoot room. If I were you I'd wait for warmer weather, or find a better cleaner heat source. Those Heaters will ruin surface prep etc....

Don't get impatient, it will ruin all of your hard work.
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