Questions about primers, prep and such, for parts

[71CHEVYSHORTBED402]

Not for body work, but brackets, horns etc.

Self-etching primer: I'm a bit confused when to use self-etching primer. I read where you sand first and then use the primer. I also read you only use self-etching primer on bare metal when you have not sanded.

Red scotch-bright pad: If down to metal, seems a red pad is a nice final surface prep. prior to cleaning, do you agree? If this is done, can I use a self-etching primer or self-etching chemical?

Self-etching Vs epoxy primer: perhaps I misunderstood, but I read where you use both in primers in some instances. I also read you use one or the other, not both.

Self-etching primer Vs self-etching chemical with epoxy: If either self-etching primer or epoxy primer................is it a basic rule of thumb that:

1. Do not use a self-etching chemical with self-etching primer.

2. Do use a self-etching chemical when using epoxy primer on bare metal.


Wax & grease remover: Is it a good idea to use wax & grease remover with either primer? How about wax & grease remover followed by a self-etching chemical?


Thank you.

[Foot Stomper]

I hope I can simplify this for you.

There's only two kinds of primers.
1) Epoxy Primer - this is a corrosion resistant primer used on bare steel only.
2) High Build Primer - this is a urethane sandable primer as it contains fine talcs that allow sanding with fine sand paper as a final step before painting.

Self etching is a commercial term used to sell primer that "sticks". If you think about it, what good is a primer if it DOESN'T stick??

Wax and Grease remover is a product used to Final Wipe an area prior to sanding, priming or painting. TIP: Don't confuse this product with "Reducer" as some folks do... they are NOT the same and you will have failures if you use them incorrectly.

[Bigboy4613]

2 schools of thought here, self etching primer followed by a urethane 2k primer . Then you have metal prep followed by a epoxy primer. Those are the two main ways of going from bare metal up. Self etching primers have phosphoric acid in them and is why they are good over bare metal and they have a 2nd benefit which is after a short flash time you can put a multitude of different products on them except anything else containing phosphoric acid. Now to metal prep and epoxy. Metal prep is phosphoric acid based as well and after it is used and has conditioned the metel epoxy primer is used to seal the metal. Both ways are good but two phosphoric based products should never be used together it creates problems.

[Bigboy4613]

This might help i was lucky eenough to find a 64 c10 with original paint on the entire truck. When i stripped the bed sides i used a 3m paint buster pad on my buffer that uses 8" stick on discs, i used 40 grit 1st removing 90% of the paint and primer and finished with 80 grit leaving clean shiny metal. Being that bare steel "ferrous metal" starts to flash rust immediately in high humidity i sprayed a water based pre cleaner and went over 2x2 section with a wet red scotchbrite pad drying it immediately and when i had 1 bedside clean i sprayed a good coat of self etching primer on it and waited for it to flash off i then sprayed 3 coats of a good 2k urethane primer. Now that metal is sealed and no longer subject to rust. Now to my tailgate, it took a couple of nights to strip the tailgate because of its shape and lettering and spots where the paint had been scatched to the bare metal and surface rusted i used the metal prep and epoxy on it. The reason for that was because of the shape of the tailgate i couldn't get the metal clean and pristine like i could the bedsides because i had to use a comibination of aircraft paint remover and abrasives to get the paint off. I used ppg one choice metal cleaner and metal coditioner which is to different products and then i sprayed a few coats of epoxy primer on it and i am confident i have a great base for my paint job.

[71CHEVYSHORTBED402]

Great info., thank you. Sounds like a red "scotch-bright" pad is a good final metal prep, before cleaning (i.e., wax & grease remover) and conditioning (i.e., metal prep). Sorry about the confusion in the OP, I wrote "scotch guard"......YIKES!

If I'm reading you guys right, the process is:

1. Wax and grease remover (i.e., metal cleaner). You can use this prior to sanding, priming or painting. In other terms, I could: Sand/scotch pad....then wax grease remover, using a cloth to wipe it off (i.e., no water)....then metal prep & epoxy primer or self-etching primer.

2. If self etching primer: Apply, flash and then apply high build primer (e.g., urethane 2k primer) or paint.

3. If epoxy primer: Metal prep then epoxy primer. If I understand correctly, the epoxy has to dry before the next coat, but if it sits say 24 hours or so, then you need to scuff it up.

4. Phosphoric acid: Never use two chemicals with phosphoric acid, such as metal prep followed by self-etching primer.

5. One last question, (we can only hope). I believe I've read you can leave epoxy primer without a top coat. In other terms, it provides the metal a good barrier from water vapor. If using self-etching primer following by high-build primer, you need to top coat relatively quickly, because it doesn't provide that barrier, or rather, it's a temporary barrier pending paint?????????????????????????

[Bigboy4613]

You are a quick study and almost there. You don't have to let epoxy primer dry before additional coats just a good flash time but epoxy primer is a great seal on metal but additional coats won't give you a lot of build. The advantage of epoxy is great seal on metal and you can do body work on top of it. And self etchin and a good 2k urethane primer will provide a really good seal as well acting as a moisture barrier its just not that you would want to put a self etch a 2k primer outside in the elements for for a few years and then sand and paint. Epoxy is the best as a moisture barrier damn tough stuff 2k urethane primer is not reversible meaning it wont absorb moisture but left outside in the elements the pigments and extender pigments will degrade over time and let the elements through.

[Bigboy4613]

Dont worry about asking questions i will be asking a bunch of technical questions about how these trucks are put together myself. Paint and coatings are what i do for a living. Painted cars for years now i work in the manufacturing of paint so i have an unfair advantage there. Its so cool to be able to go to the chemist who design and develop paint and ask and learn from the source.

[Foot Stomper]

Tony,
Do not use anything under epoxy primer. Ever. Not even metal prep.

Drop the "self etching" terminology as it doesn't pertain to anything. All primers and paints are "self etching". It's only a sales term to sell that it sticks...

Typically, guys will blast, epoxy prime and let it rest. They go to work on repairs, body work, welding etc while only taking off the epoxy where they are working on it. After the work is done, new epoxy is applied to exposed steel, then body filler where needed, then a high build urethane primer for final body work, then paint.

It's just that easy... except for the hours of labour...

[Bigboy4613]

Not sure where you're getting your info but you completely wrong about self etching. I work in a plant where paint is made and self etching refers to the chemical reaction between ferrous metal and phosphoric acid and its real and all primers and paint are not self etching. Adhering and etching are two totally different things. Thats not an opinion thats fact.

[Foot Stomper]

Ok then.
Carry on to confuse.

Btw
You're not the only one here that's had a career in paint manufacturing and sales.

Cheers.

[MARTINSR]

The term "Self etching" is an acid etch primer, it is unique and not like other primers. I has no filling qualities, it is strictly for adhesion.

I use to be a big believer in it but have changed my ways an lean more towards epoxy primer for over bare metal.

Brian

[my56chevytruck]

Follow FOOT STOMPERS original post, he's got it down right. Use your "epoxy primer" on bare metal, and high build primer to finish with, of course sanding with 200 grit and above to get the surface scuffed enough to paint depending upon what the surface finish you are looking for. you can also wetsand for a great surface finish. Also, if you can pull up EASTWOOD.COM or call them. They are great for help either way.

[71CHEVYSHORTBED402]

Thank you guys, here's my education. Appreciate any corrections, etc........For the record, these are just parts and there's no visible rust.

1. Final grit should be heck, I don't know. Lots of info. and variances. 80-120 grit by some accounts, and approx. 400 by others. Correct me if I'm wrong, I'm guessing 80-400ish works, depending on what it is you're painting. Considering I'm just painting parts and have no need for urethane primer, I'm back to the maroon pad. They're about 320 grit. Unless I'm mistaken, scouring/sanding is a form of etching the surface.


2. Then Clean: Use lacquer thinner, mineral spirits, acetone or wax & grease remover. You can follow that up with isopropyl alcohol to lift additional contaminants. Really, there doesn't seem to be any shortage on products used to clean surfaces. On a side note, I've read you risk fisheyes by using lacquer thinner or mineral spirits, and imagine that may apply to alcohol and/or acetone as well. As a rookie, seems wax & grease remover is a safe route, and perhaps isopropyl alcohol.

• Use a lint free towel to wipe it clean. You can even follow that up with a tack cloth. At this point you're ready for primer.


3. Epoxy Vs Self-etching: Some debate over the existence of self-etching primer. However, this is my understanding of the differences, whether they're real or not.

3A. If self-etching:
• Apply any body fillers first. Doesn't apply to me, but just saying.
• You don't have to scuff up the metal surface because of the acids for adhesion.
• If you leave it sitting around for say 1/2 hour or more, then scuff it up before the next coat in your process.

3B. If epoxy:
• This provides better resistance to the elements than self-etching primer.
• You do have to scuff up the metal surface for adhesion. As a metal prep. goes (i.e., phosphoric acid), perhaps it's best to use it only if the manufacturer paint line calls for it.
• Apply any body filler afterwards.
• You can leave it sitting for a longer period of time before having to scuff before the next coat in the process. Word is it's a (*&^^ to sand.
• Guessing here, but I believe it has some qualities to stop rust, say rust that's not visible. Not to be confused with a rust converter.


I think I'll:

1. Scour following any sanding & brushing. At this point the parts are clean. I won't bore you with the details, but I clean and tuck them away for another day. Despite the Nevada climate, that may mean I hit them with white vinegar and neutralize. Regardless, I'll be revisiting all the parts for prep. I do not have a blaster. Not yet anyway (cough). Really though, on a scale 1-10 for rust, this truck is a 1.

2. Wax and grease remover.

3. Epoxy.

4. Paint.

5. Two stage is pending. Not sure on that one yet. The frame will be Master Series stain black. Whether or not the core support etc. sees a clear coat is pending, but they'll likely be painted satin black. I sure like the looks of powder coat, but the separation etc. scares me off a bit. That and once it's scratched there are only two options, ignore it or start over.





Good videos:
https://www.youtube.com/watch?v=jvUhchmHTCM
https://www.youtube.com/watch?v=-bSE1AUKxQ0

[71CHEVYSHORTBED402]

BTW Big boy, I'm definitely not the best source for electrical. I just dove into it and received a lot of help from this site. That said, if your project is similar 71 C-10 with A/C, I can tell you exactly how it's wired in simple terms. Less inside the fuse box anyway. That's a place I'm not sure I want to visit.

[scottmitchellrose]

To add a question to the thread-
I used DTM (direct to metal) primer on my bed and cab after blasting them (industrial fire-hose type blaster). I was ignorant to apply enamel paint to the bed afterwards (no sanding of the etching primer DTM- which I assume was correct?). Can I sand that with say 500 grit and continue to paint- or do I need to apply an inbetween stage like primer?

For the cab- only the DTM is on it. It has been sitting 5 years in my garage like that. Can I go straight to a primer or do I need to now sand that self etching (DTM) primer first? Thanks a lot,

[mongocanfly]

You'll need to sand if its outside the recoat window of the primer....at 5yrs, your gonna be sanding
Was that epoxy primer you used after blasting?

[scottmitchellrose]

Thanks- the bed has been outside, but cab in the garage this whole time.

[HAULIN' IT]

Scott, Exactly what product did you put on the parts? Brand, part numbers ect? Unfortunately it is NOT near as simple as FootStomper implied above. You stated DTM & then "etch primer", again that could be multiple things. I would say your "ignorance" may have really saved all of the base work you did, as most primers 5 years outside in the weather could suck up a fair amount of moisture. Same with a damp garage. Lorne

[scottmitchellrose]

ooh, boy, HAULIN' IT- I'm not sure. I was learning from my cousin who unfortunately became ill with cancer and is now gone. I can tell you that he did not like epoxy- he preferred acrylic enamel for paints, and a can that said DTM self etching primer (army green) is what I put on the bed.
The cab I did put epoxy primer on- from a local paint store (name has escaped me- thought it was United Coatings)

[HAULIN' IT]

You are not helping your own cause, Just kidding! Sorry to hear about your cousin, cancer sucks!
As to trying to give you a realistic answer without knowing much about what products you have on there can only be a general "guess".

On the bed, ASSUMING there is hardener in the enamel, you will be fine to sand with 500-600 grit & proceed. To test if you are not sure, a clean towel soaked in lacquer thinner placed on the surface for a few minutes & then removed will tell the tale. If nothing happened, its catalyzed, if you have a rag stuck in the paint & a soft goo-mess, its not & needs to come off. I would do a spot down low, inside the bed...someplace not in plain sight. 5 years later shouldnt be a problem, but dont invite one anymore than you need to to test.

On to the cab, You mentioned epoxy, that is better for you having it sit than an acid etch wash primer. Some epoxies have a "re-apply" requirement outside the re-coat window (as in you have to sand/scuff & then re-apply more epoxy) others dont, just sand/scuff & go onto urethane primer.

Again, thats why it is best to know the products & have the p-sheets handy for those products. Lorne

[scottmitchellrose]

Thanks a lot, Lorne! When I'm able to get to it I'll post a pic and send.
Scott

[nsb29]

The best thing is to keep it simple strip it to bare metal, wipe it down with a wax and grease remover, give it three coats of SPI epoxy primer, if there is no welding or body work to be done apply your high build primer within the recoat window.
If it goes beyond the recoat window it will need to be scuffed/sanded and degreased before applying your high build primer I prefer polyester high builds like slick sand or feather fill over the 2k primers

[67C10Step]

I posted this photo in the what did you do to your truck section but these are brand new parts from Mar K and were bare metal. Scuffed with 80 grit, cleaned with water based cleaner, cleaned again with SPI solvent based wax and grease remover, and then sprayed with SPI black epoxy primer.
All I will say is if you think your body guy is charging too much ask him to let you lend a hand in prepping parts. I know I have 8-10 hours total in these three parts sanding, cleaning, prepping, spraying, and then cleaning up.

[scottmitchellrose]

True 67C10- I can't figure your photo out. Those panels look to be twice the size they should be!

nsb29- thank you as well. I'll post a pic when I get around to it (hopefully soon...)

and Lorne of course!

[67C10Step]

Originally Posted by scottmitchellrose

True 67C10- I can't figure your photo out. Those panels look to be twice the size they should be!

nsb29- thank you as well. I'll post a pic when I get around to it (hopefully soon...)

and Lorne of course!

Ha, ha! It's all about photo perspective I guess. The pieces are probably 15 feet from the back wall and 15-20 feet from the bikes in the background. Makes them look bigger I guess.