Body Panel Rust Removal

reallylongnickname

reallylongnickname

Promoted Users
I want to remove rust from body panels and fenders then shot coat of primer. I’m concerned about sand blasting warping the panels. Thought of maybe chemically removing rust, but auto supply shops suggest using POR etc. I’m sure this subject has been discussed, if you could refer me to the subject thread, that would be appreciated.

* I’ll post pics when I get home
 
Use the Search button above right. Type in POR-15 and be prepared to read for a while.

Bottom line, you are better off media blasting the metal. The only way it warps is if you have the pressure way too high and overheat the metal.
It is best to keep your gun at a slight angle to the metal and then use a sweeping, side to side motion.

This is the hood on my 1968 GTX project.

Hood Separated 2.JPG


Here you can see the inner supports media blasted and where I have started media blasting the backside of the hood skin.
Inner Supports Media Blasted.JPG
 
If you blast panels you have to do the whole panel so it "warps" evenly. Abrasive blasting warps panels by stretching the surface from micro-peening- each sand particle hits the surface hard enough to make a crater and pushes the metal outward. This is only happening on the very outer skin of the metal, which lengthens the outer skin and the opposite side of the sheet is not stretched so you get a raising effect. This is super noticable if you blast a hood or trunk lid with open inner bracing, and you blast the inside of the outer skin through the holes in the bracing. You'll get an outline of the brace opening pattern on the outside skin.

Blasting doesn't create nearly enough heat to warp metal, the surface temps barely rise above ambient.
 
Last edited:
'68 Coronet R/T said:
Use the Search button above right. Type in POR-15 and be prepared to read for a while.

Bottom line, you are better off media blasting the metal. The only way it warps is if you have the pressure way too high and overheat the metal.
It is best to keep your gun at a slight angle to the metal and then use a sweeping, side to side motion.

This is the hood on my 1968 GTX project.

View attachment 15045

Here you can see the inner supports media blasted and where I have started media blasting the backside of the hood skin.
View attachment 15046
Click to expand...

So you do remember you have a GTX project :)

I think getting that rust out of there is worth the small risk you will warp it. I don't think focusing around in that corner with all that support will carry much risk of warping it anyway. The rest can be done with the abrasive cookies or DA
 
JimKueneman said:
So you do remember you have a GTX project :)

I think getting that rust out of there is worth the small risk you will warp it. I don't think focusing around in that corner with all that support will carry much risk of warping it anyway. The rest can be done with the abrasive cookies or DA
Click to expand...
Yes, just have two others to get done first. :(
 
Please critique my blasting setup:
- 9 hp compressor
- 3/16 hole diameter at nozzle
- 3/8 inner diameter hose

Also, what would be ideal psi for say, 18 GA body panel?


20210530_213446.jpg
 
I would start low around 30 psi and bump it up until you get it like you want. I don’t think anyone will have an exact answer for that blaster. It will also depend on your media.

Don
 
I guess the forum is the place to express opinions, so let me put a different spin on blasting.
Several decades ago ( around mid 60s) I bought my first project car, a 55 Chevy HT from Tennessee. It had serious rust under the body side trim, and some other spots, but not too much. Being a rooky, I rented a very large compressor on its own trailer, and a pressure sand blaster. Don't remember what grit sand I used, or the pressure, but I was impressed with the sparks it created, so I guess there was some pressure involved. It was only used to remove rust, not paint, and after blasting there was a distinct crown where the trim goes. Now I don't think that was caused by heat, it was thousands of tiny hammers hitting the metal with pressure and stretching it. The crown came out toward the basting stream because of the crown of the panel. Stretched metal goes the same way of the panel crown, or the crown of the area in question, its the path of least resistance.

When working with metal, sometimes it seems like one spot or area just won't shrink, but if you examine the area closely, you might find that it is actually a reverse curve. In that case the metal will shrink toward you, its the path of least resistance.

So my two cents worth is to only blast what is needed. Use crushed glass and keep the pressure and volume down. That little siphon gun will not likely do much damage anyway, the concern will be in actually blasting the rust off.
 
Its either blast pressure or distance away from the panel that causes problems. Sometimes you try to blast low pressure and you cant even siphon up the sand. When that is the case, just stay farther away.
reallylongnickname said:
This the panel and area of concern. Actually, the rest tof the panel is very decent. You say I need to do the entire panel?
View attachment 15298
Click to expand...
IT does not matter how you blast that area if you leave those two parts attached. The rust is between those surfaces and unless you separate them, the rust is going to return.
 
anotheridiot said:
Its either blast pressure or distance away from the panel that causes problems. Sometimes you try to blast low pressure and you cant even siphon up the sand. When that is the case, just stay farther away.

IT does not matter how you blast that area if you leave those two parts attached. The rust is between those surfaces and unless you separate them, the rust is going to return.
Click to expand...
He's right, the bracket on your panel looks as bad or worse than this one did. Just depends on how long you expect it to last.

zfOSX1.jpg


IP6yjo.jpg


S4kGRt.jpg
 
Don’t waste your time with POR, IMO. I wouldn’t hesitate to carefully blast that, or just clean it good and use Naval Jelly or similar. Wrap in plastic wrap and let it do it’s thing, maybe overnight if it’s heavy rust. Remove any tar before blasting.
Dave
 
I don't know if this got mentioned, but angling the media stream can minimize warpage as well. Push the old paint off from the side and the metal gets more of a "glancing blow," straight on is bad news.
 
You must log in or register to reply here.
Back
Top