Bare metal epoxy primer for truck frame

[mrmikey]

Many vehicles you dont need to drill acess holes.

Funny story.
Many years ago I had just bought a Mazda Protege, (one of the best cars I ever owned) and I wanted to get it sprayed. So to get a good job done especially inside the rocker panels I took off the plastic kickplate on the 4 sills. Underneath each there was a slot over an inch wide and other than a couple of strips joining each side together it was the full length of the rocker. I figure great, he won't have to drill any holes and they'll be able to do a good job.
I'll be d***ed if they didn't drill a hole at each end of the slots, don't know if the guy was blind, stupid or both but I got it back and here were 8 plugs, 2 for each rocker panel at the end of each slot. Never could figure out where his mind was...if there even was a mind involved

 

[Snobdds]

Back when I was painting, overcoats to any epoxy had to be performed within 8 hours or less or it wouldn't stick. I spent many long days when using epoxy primers and paints. I spent 20 hours on one event when I painted a boat. I wouldn't do that again.

When I repainted my 1988 toyota truck with epoxy primer, I waited 2 days. It is still holding up today. The problem I had was it was my first paint job. I didn't put enough mill thickness down to build up the paint layer. I now, 12 years later, have some of the top coat wearing through. Plus I used a single stage paint. Mistake.

Two year ago we painted my dad's 1991 toyota truck. I did not use epoxy primer and did do a paint and clear application. Much better and it's how I am going to redo my 1988 truck this spring. I'm an armature at this, but we like to take the toyotas up to the cabin. It's the best vehicle for that. So I learned how to work on them because it seems nobody likes to work on 1980 vehicles anymore, or knows how for that matter.

 

[Hay Dude]

So the next “plan” is to sandblast the frame as much as we can get to, then apply a product called “Rust Kutter” to the metal to change the rust from oxide to phosphate.

https://www.amazon.com/Rust-Kutter-Converter-Professional-Repair/dp/B001U1GW82/ref=asc_df_B001U1GW82?tag=bngsmtphsnus-20&linkCode=df0&hvadid=80333185695387&hvnetw=s&hvqmt=e&hvbmt=be&hvdev=c&hvlocint=&hvlocphy=&hvtargid=pla-4583932713509177&psc=1

I read several reviews and one very extensive review (Repair Geek) with pretty comprehensive tests gave Rust Kutter the highest ratings at bonding to the rust, chipping and bending adhesion.

OR

I can go “balls to the wall” and remove truck frame, but then again, can I?

So this is a double truck frame. I would really prefer to separate the inner from the outer. Remove all the huck bolts, frame suspension bolts and crossmembers, then remove inner frame.
Question is, can you remove the inner frame and leave the truck cab, engine, etc supported by the outer frame? Or do you remove one side (both inner & outer) sandblast, treat & paint, reassemble then do same on other side?

Of course we are talking about 5 times as much labor cost, if not more.

I don’t know if I’m over thinking this or not? There is some rust jacking between frames-maybe 3/16”-1/4”.

 

[mrmikey]

Years ago we replaced the complete double frame (inner and outer) on a FWD, thankfully I wasn't involved. It was done by removing one complete side at a time and it was a complete disaster both for time and having to replace parts that weren't 'bad' but that were destroyed in removal. When you start removing steering boxes, and other front end components as well as crossmembers, engine mounts, torque rods etc you're looking for trouble. Not to mention the cost of the Huck bolts which are a pia to install on an already assembled truck or the cost of the the GR8 bolts, flats and locknuts if you go the bolt route.
Even separating the frame members without bending them will be hard. Especially where it was a plow with a wing as the frame probably already has a bend in it from the side push.
Your thoughts about wanting to do it are good but I can see it being a very expensive and time consuming project, I personally wouldn't do it.
Even blasting it will be a pain, air lines and electrical are going to be damaged but at least they are 'easily' repaired.
IMHO, I'd go with your original plan, blast and paint with either paint or the Rust Cutter you mention and a good application or some creeping rust preventative to soak into unpainted spots. Remove any parts that are easily removeable and in the way, fuel tanks, battery box, exhaust hanger etc
On a side note, we got away from double frames because of the reason you mentioned and went with 7/16" 120K HSLA single frames.

 

[Hay Dude]

Yeah I don’t want to overthink this too much. Wish it was a single thick frame. If I had stupid money, I would replace with single frame.

Would diesel fuel be a suitable creeping oil? Or is that too runny/thin?

 

[ray66v]

The term "epoxy Primer" is used more for marketing purposes. It's got to be good if it has "epoxy" in it right?

Technically, any primer with hardener is an epoxy primer.

Do you need a primer with hardener in it for a truck frame? It doesn't hurt, to do so, if as stated you apply a finish coat in the recommended time interval, usually 8 hours. These products are designed for wet on wet applications, which means they are applied one after the other, so they bond together.

It is not necessary to use a hardened primer on a truck frame, and you may be better off if you don't because of the limited re-coat times. Go past the re-coat time and you should sand every part of it to get adhesion, which is difficult and in some cases all but impossible.

The more critical step would be to use a primer that is made to go directly on bare metal. No, not all primers are made to do this.

A good direct to metal primer will have some sort of etching ability. This can also be achieved by using a metal prep, or coating.

I prefer to use a wash primer when I want to be sure of a good etch. You can follow that with an industrial enamel primer, and have excellent results without re-coat time worries, or having to sand. That will provide an excellent level of protection. It's also cost effective, and easy.

 

[Hay Dude]

If I use the Rust Kutter, or Ospho, would that lessen the need for a hardened primer?

I think the Rust Kutter not only changes rust to iron phosphate, but it prepares the metal for the next coat to bond to it.

 

[mrmikey]

Would diesel fuel be a suitable creeping oil? Or is that too runny/thin?

I'd say too thin and too easy to wash off. You want something that's thin to apply so it creeps and then the solvents evaporate leaving the 'substance' behind.
I 'obtained, cough....cough'. the dregs from the bottom of a 45 gallon barrel of Fluid Film as it was too thick to spray from the proper gun. I warmed it up and used a sprayer made from a 20lb propane tank to apply it. Covered great but it didn't creep like I wanted it to because it was too thick. Mind you what it did cover lasted for years.

 

[alexpops]

Mix some waste oil with the diesel. You'll need to re-apply fairly often, it's messy, frowned upon by DOT's and asphalt parking lots, but it works well. Also relatively cheap.

 

[bigtiller]

For what it's worth, JD used to spray cotton pickers/strippers that were to be shipped overseas on container ships, with fluid film to protect them from ocean waves spraying salt water mist.