Don 68

I blasted the bare frame of my 68 last weekend using the black diamond material I got from Northern Tool. I'm waiting until this weekend when the weather warms into the 70's before I paint it. Do I need to wash the blasted frame to clean it before painting or could I paint directly on the blasted frame? I would think that cleaning it with soap and water could cause rust to start on the inside of the rails and seams. This is a very solid frame and I don't need any rust problems. I'm going to spray the frame with three coats of SPI Epoxy Primer and then I plan on treating the inside rails after painting with SEM rust preventer internal frame coating which they told me is a cavity wax.
Thanks,
Don

DUB

Don.
You put the "cart before the horse"...so-to-speak. Basting the frame clean and then waiting a week or two is allowing rust to start...and it is as you are reading this post...you can count on it. Moisture + air + bare steel = RUST.

There are some products that contain phosphoric acid which will eat the surface rust off and prep the steel for a primer or whatever. The stuff I use is from NEXA is called "deruster"...I know back in the day DuPont made something and I think PPG does also. So the choice is your because it mixes with water....and when mixed together in the correct ratio in a solution that when applied and scrubbed with a red scotch-brite pad and GLOVES...it will remove the surface rust...even the rust that you can not see. Take a jewelers loop (10X magnification) to the steel and look...you would be amazed on what you might see. Then it has to be rinsed off and dried. This is where the problem will begin due to water will get inside the frame and there is no way of stopping it.

So...either epoxy it and move on and hope for the best...or prep it and spend major time raising the frame and rotating it to get all the water out and try to dry it out by blowing air in every hole possible...UNLESS you have access to a bake booth and can do it at a shop that can run it through a bake cycle or two to dry it all out and then apply the epoxy when it has cooled.

ALSO...seeing how I am NOT the source of information on SPI products...you might want to talk to either SPI or "porchdog" here on the forum because he uses it and knows it very well and could tell you if JUST shooting the epoxy by itself is CORRECT or not. Most epoxy primers are NOT a stand alone product...and usually require a top coat to seal them and prevent them from failing.

DUB

Don 68

The waiting time is because it was to cold to spray outside after I spent about 7 hours blasting. I work during the week and spend my off time on this hobby. After reading your post I went inside the shop to check the frame for any new surface rust and didn't see any. If I have to use phosphoric acid and scrub it before I spray to clean it I will. I want to do the best job I can. That's why I asked for advice about cleaning. Rotating the frame to get the water out as I blow dry won't be a problem.



I made this rotating jig with two engine stands to blast and paint the frame. Works like a charm. I took this picture just after I blasted the front and left side.
Don

929nitro

Very good idea for a frame rotator.

DUB

The choice is yours...if you looked at it under magnification and it is fine...that will be your call on that one. I have experienced blasted steel not rusting right away...and I also have come in the next day and it has surface rust on it....so you could be OK...but only you can determine that.

Just make sure that you verify if the SPI product is a stand alone product that will last FOREVER....because if it is NOT...then you will need to apply another product on it..because doing what you are doing is something I KNOW you do not want to do again in ten years...right?

DUB

Don 68

Thanks, I had to come up with something so I could blast and paint it. You have to get creative when you work by yourself. This thing weights 300 pounds and I didn't want to hurt myself by lifting and turning it over while working on it.
Don

persuader

Cool jig Dude.

Don 68

Thanks for the insight. Just to make sure I've decided to scrub and clean it with phosphoric acid, rinse it really well and dry it Saturday then epoxy prime it Sunday. What I've found out is the SPI epoxy doesn't need a top coating where the sun doesn't shine although it does have some UV protection. Your right I don't want to do this again in ten years but I did a frame on restoration on this car about 28 years ago. At that time I sprayed what I could of the frame, front and rear suspension parts with black Imron. Most of the parts still looked good and had very little rust on them.
Don

DUB

I am not so worried about any UV resistance...because I know the sun would rarely...if ever hit the frame for any length of time...it is more dealing with the epoxy being porous and needing something on it to seal the epoxy itself.

Much like the E-coating on GM parts....it is a great primer...but in time it can fail due to it is not designed to be left as itself.

If SPI says it is OK...then I would go with it.

Just a "heads-up"...if you are going to phosphoric acid the frame...you better have eaten a good breakfast that was packed with energy food.....because this process is something that you do not "dilly-dally" on. This is why I mentioned using a bake booth...because once you hit it with water...and then the acid solution...and then rinse it...you have to get it dry really fast...You might consider doing a section that is controllable at a time...instead of doing the entire frame at one time. Do a small section...you will see what I mean.

DUB