Bodywork on Fender

[40fordpu]

1940 1/2 ton pickup with what I believe to be very old paint/rust. I have removed most of it with a 40 or 60 grit disc. But what is the remainder left over (and its not "pitting" as far as I can see). No matter how many times I go over it it just remains. Can I do primer/body filler over it or will I have a problem with lifting later? Thanks for your time and response.

[alanwoodieman]

you need to kill the rust or it will come back. ospho from our local true value hardware store works very good.

[v8nut]

I would use RUST 911 from Harbor Freight

[john greco]

Ospho

[Kube]

Originally Posted by 40fordpu

1940 1/2 ton pickup with what I believe to be very old paint/rust. I have removed most of it with a 40 or 60 grit disc. But what is the remainder left over (and its not "pitting" as far as I can see). No matter how many times I go over it it just remains. Can I do primer/body filler over it or will I have a problem with lifting later? Thanks for your time and response.

I'd sand blast it.

[Tinker]

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Blast or Ospho. Blast obviously better. But treat with something (like Ospho) so it doesn't flash rust.



I could always get Ospho in florida cheap. Marine area I guess.


Only ACE hardware carries it here in MN. $30 a gallon.


.

[RalphM]

As Kube said, I think sand blasting is the only way to be sure it’s all the way down to bare metal.

[RalphM]

But treat with something (like Ospho) so it doesn't flash rust.

That’s the nice thing about being in the Arctic, what’s flash rust? Most of my car has been bare metal since October.

[Tinker]

Originally Posted by RalphM

But treat with something (like Ospho) so it doesn't flash rust.

That’s the nice thing about being in the Arctic, what’s flash rust? Most of my car has been bare metal since October.

True. A blasted bare metal sheet in the subtropics rusts while you are looking at it. 80 degrees and 90% humidity at 8am. Now MN Had to run a humidifier all winter to get above 30 now. But snow is melting and I'm land locked. Time for the dehumidifier.



Oshpo is basically just phosphoric acid (5%). Concentrated citric/sugar acid. In the states look at famous cola ingredient listing. It has phosphoric acid as a citric/sugar substitute and can clean a penny with time. The south of the border same brand cola just uses a milder taster mild cane sugar. Same thing really, just a concentrate of sugars.



Badass project by the way.

[marko39]

i use bill hirsh metel prep even after blasting to remove the rust in pits and prevent flash rust. in your case first spray with muratic acid, neutralize with baking soda, and then the metal prep.

[Bob NH]

I'm on the side of kube and Ralph ,blasting is the only way to get it all out of the deep pores. Just don't go crazy with pressure ! Does not take much to warp and create other issues.

[35fordtn]

Maybe I’m too simple minded but simply blasting, then epoxy primer seems to be enough to me??

[Tinker]

For sure blasting is the best and if you can lay down sealer within a short period.


If not ospho or other metal etchers will work.

[deuce_roadster]

I ALWAYS etch after blasting. If there is no rust and I do plastic media blast, I DA it and etch it before catalyzed sealer, then the normal build primer, last seal coat and then color.
Any bare metal needs to be etched as there is oxygen in the air no matter what the relative humidity is.

[Frank Miller]

At Pro Shaper they use naval jelly and cover it with saran wrap overnight so it does not dry out. Does a surprisingly nice job.
http://www.proshaper.com/

[40fordpu]

Great advice from everyone. Appreciate the responses. But can someone explain to me how you put metal etchers on and then wash it off with WATER and don't get rust right away (at least this is the process I am reading for some of them)?

[Tinker]

A product like Oshpo can leave a white residue. You want to remove that. Wash dry/sand/shoot etc. To my thinking it's a process that is best done with your elbows in it. Meaning once you start, you don't wait. Sanding,sanding, then sanding after every step. A nice paint job is very labor intensive. Paint and sealers have windows too.

Oshpo or other etchers will allow you to shelf a part. But then theoretically, you start all over again if you pick it up again after a week or more.

Etchers convert the (mynute/minute) rust to a inert metal state and give it a "bite" to hold paint.

If you blast, etch, then epoxy seal. It'll last a while, week/days/yrs(if you don,t repaint). After two weeks with a epoxy sealer you will have to sand to give bite, to add any high fill or base coat. Best to follow your paint supplier cure/application windows.

Just my experience. Or my sanding experience. I'm certainly not a paint professional. nor to claim to be a car professional of any sort.

[marko39]

Originally Posted by marko39

i use bill hirsh metel prep even after blasting to remove the rust in pits and prevent flash rust. in your case first spray with muratic acid, neutralize with baking soda, and then the metal prep.

as a side "benefit" of muratic acid you wont have to trim those pesky nose hairs.

[Cecil/WV]

Originally Posted by 35fordtn

Maybe I’m too simple minded but simply blasting, then epoxy primer seems to be enough to me??

This is what I would do!

[Kube]

Originally Posted by deuce_roadster

I ALWAYS etch after blasting. If there is no rust and I do plastic media blast, I DA it and etch it before catalyzed sealer, then the normal build primer, last seal coat and then color.
Any bare metal needs to be etched as there is oxygen in the air no matter what the relative humidity is.

Exactly!
You do exactly what I do.
And, if I may expound a bit...
I have my body and panels plastic media blasted. I will never have any chemically dipped.
As you surely know, the plastic will not remove rust. That's fine as I cut it away and install new metal.
Pitting? If it's light, then the DA comes out. If it's deep, then I sand blast.
All of this is done in a timely fashion. In other words, I clean only the metal I know I will be able to seal promptly thereafter.
I finish my vehicles so they will stand the proverbial test of time. The earliest cars I'd done are now over 40 years old and still, with only minor exceptions look as good as the day they were finished.