Abrasive Blasting Auto Body Panels.

[kiwiandy]

Hello.

Im interested in the general opinion on sand blasting body panels? I have a 1950 Ford Coupe of which I have removed the majority of paint back to bare metal by sand paper. The thing is, in some areas on the rear quarters there is a black staining in the steel. It was suggested a light sand blast would remove it and also leave a good substrate for the primer.
Question. Will blasting cause issues with the steel ie. work hardening? Provided it is done by an experienced professional, would it warp the panels? Thanks in advance:)

Andy.

Auckland, New Zealand.

[snotzalot]

Sand blasting distorts the metal, no matter how good your professional is.

[Hairy-Neil]

High crown panels you'll get away with. Low crown it can/will destroy in short order, but then, I've seen that done with a DA sander too.

[steve.murphy]

Andy, Here is a good one Randy wrote about rust removal:

http://www.metalmeet.com/forum/showthread.php?t=2257&highlight=%22rust+removal+willys%22

[Streetwerkz]

We media blast body panels all the time with no distortion.
one client in particular has us do vintage Jag stuff that is mostly 70 yr+ old aluminum with no problem

Several things to know
1, be patient
2, use a media that does not build heat (60 grit aluminum oxide)
3, do not crank the psi up to a ridiculous level for the sake of speeding up the project (40-50 psi is best for sheet metal)
4, keep your gun to part distance at 1 foot or greater, and at a 45­° part approach angle

[CARS]

Sand blasting distorts the metal, no matter how good your professional is.

I agree with Josh's post.

I sublet out 90% of my blasting and the guy is great. Uses a compination of Ash from a coal-fired ethanol plant, glass, and silica sand. Once in a while a hood will be a little wavy, but who is to say that someone wasn't sitting on his/her hood in a parking lot in 1976 smoking a fatty?? By 2010 the paint isn't in good enough shape to see if it was straight before blasting.

I don't have an air system capable of doing a whole car in a day like he does, but I still do an occasional part with great success.

There are some coatings such as powder that I can see creating some damage. Some of that stuff is just plain hard and indestructible. But for Andy's situation a light blast of sand will do the trick.

[kiwiandy]

Hello.

Thankyou all for your input. The guy suggested to do the blasting apparently has a Thunderbird down getting blasted at the moment. I might go and have a look at how that turns out to gauge the quality and his skill level.
Andy, Here is a good one Randy wrote about rust removal:

http://www.metalmeet.com/forum/showthread.php?t=2257&highlight=%22rust+removal+willys%22

I had a read through this earlier post and it was very helpful. That rust staining is pretty much identical to the issue I have with mine. Im really keen to try that method but what is Navel Jelly? Ive checked in mine and found some navel lint from my T shirt but certainly no jelly!;) Can some body tell me the active ingrediants and the quantity so I can match something off the shelf over here? Is Gibbs spray going to be a good coating to finish with?
Thanks.
Andy.

[CARS]

Im really keen to try that method but what is Navel Jelly? Ive checked in mine and found some navel lint from my T shirt but certainly no jelly!;)

:lol:


The main (only??) ingredient is Phosphoric Acid. It's just in a jell form so it clings to the surfaces better.

[steve.murphy]

Andy I google rust remover gel new zealand and came up with OxiCore New Zealand.
Maybe that's similar.
Good one on the lint!
Cheers Steve

[kiwiandy]

Cheers for that. It might be the stuff I need. I will go down and have a look and read through the active ingrediants at the hardware shop. Good to be back on track! Progress on the project has been very slow over the last 12 months. For the record, I was unable to find anything on ebay under the search "navel gel"? Does it have a trade name?
Andy.

[steve.murphy]

Hi Andy,
Google naval jelly and you will find lots of info. I saw there are several manufacturers making it.
Cheers,
Steve

[adtkart]

I have sandblasted car parts for years. That is not to say that you don't have to worry about damaging them. If the pressure is kept low, the blasting done at about a 45 deg angle, and keep the nozzle moving, it can be done. Most of the time now days I only blast areas that are really hard to get to, like the hinge and latch pillars, under side of hoods and trunk lids, and insides of doors. The larger, more flat areas are easier to ruin by blasting.

Aaron

[Mike Malott]

I've some sheet metal parts blasted by a local guy and I specifically questioned him about the possible warping issue.

He, too takes it easy, but tries to blast both sides of the sheet metal part, a bit at a time. He says this distributes and equalizes the stresses and minimizes any warping or distortion.

Mike

[kiwiandy]

Hello.
So is the warping caused by the pressure of the abrasive blasting or the stresses being relieved from the panel steel? Could it possibly cause an "oil canning" effect simular to adding to much heat? Im guessing it is pretty much one in same as the friction from the blasting would cause alot of heat.
Anyway... I took myself down the shops earlier today and picked up some coarse steel wool. I found that a product I already had in the cupboard called Jenolite was infact Phosforic (sp) acid, although it was a liquid. So I started rubbing a small rust stained area of the quarter panel. Didnt have too much luck as I couldnt remove alot of the staining. Perhaps may need to sand deeper first but im slightly concerned with removing too much steel. Here are a couple of pics. Any thoughts?

[jlrussell4]

In your pictures it looks like the rust (red) color has changed to black. You've done what you needed to do http://www.metalmeet.com/forum/images/icons/icon14.gif. You have converted the rust.

[kiwiandy]

In your pictures it looks like the rust (red) color has changed to black. You've done what you needed to do http://www.metalmeet.com/forum/images/icons/icon14.gif. You have converted the rust.
Hello.
But would that rust need to be completely removed before being primered? The old saying I grew up with was "rust never sleeps". Does anyone have experience with painting over converted rust (as pictured) and how it turned out longer term?
Thanks.
Andy.

[steve.murphy]

Hi Andy,
I dont think you will lose too much metal, if any. One thing you can do is to put some kitchen plastic over the wetted area to stop it from drying out.
You can try a sample of some rusted metal in a small container filled with the acid to see what happens.

Cheers, Steve

[Philrally]

I get a guy in Paeroa to blast vehicles when i need it. Never any problems with warping. Hes a car painter so he appreciates what we're trying to achieve.

[Dawai]

OSpho here in the states is a old name I used. It converts the rust to a phosphate the way I understood. turns it black. Phsophoric acid.. not sure what strength.

it will burn you.. use protective measures.. I got a nice one on my forearm and wasn't aware I even touched it. Till it turned bright red.

[tonkat]

I have a guy who sand blasts cars for me. What he does is turn the pressure down till it just starts to remove the paint. He holds the gun at a hard angle. He also knows how far to hold his gun to control warpage. I have never had a panel warp where it was a problem that he blasted to date. He also blasts both sides. He says that the frame behind the panel will sometimes show. Like behind a hood or trunk. Not sure why that is. It might have something to do with not being able to blast behind panel where the frame lies. He did my hood and trunk and it's pretty straight. Remember to wear gloves while handeling blasted metal. Your finger prints will corrode the metal. I had a panel corrode under some epoxy primer before. It only started to show up several months after the panel was epoxy primered. Experience is everything. Tom

[adtkart]

Ideally you want to remove all rust from panels, and blasting it one way to do that. If you can remove to the point where all you have is minor pitting, then applying a True Epoxy primer will likely stop it from spreading. There are a few different primers that claim to be epoxy. If it is a true epoxy, then when it is cured it will not be effected by lacquer thinner or brake fluid. A true epoxy stops the rust by sealing out the air and moisture, and stays flexible to avoid cracking.

Aaron

[kiwiandy]

Hello.

Thankyou for all your replies. My current thinking is that I will remove a door and get that blasted as a trial. I figure the door has a good ridgid structure so would be a safe starting point.

Quote. Aaron.
"A true epoxy stops the rust by sealing out the air and moisture, and stays flexible to avoid cracking."

Can you give me the name of a quality epoxy primer? Ideally a well recognised international brand ie PPG etc.
Thanks.
Andy.

[CARS]

I have had great luck with PPG Omni Epoxy Primer, but as you state, any name brand will work.

Better yet, you could do as me and order your next primer from a MM supporter: http://www.metalmeet.com/forum/forumdisplay.php?f=213

[kiwiandy]

Thanks Chris but I might have issues with the importation. Most major brands are available locally:) so interested in any thoughts on quality, experiences etc.
p.s Chris. I had a look at your site and I think the idea of letting the customer assist with the build of their project is great. Excellent philosophy(sp)! I would love to see it catch on! The cars you have done look great.8-)

Cheers.

Andy.

[mike40]

My advice to anyone thinking of grit blasting car panels is No,No,No,No.... Don't do it!

I had heard all the gory stories of people sending panels for blasting and getting potato crisps back and yet I also heard fourth or fifth hand of a guy called Joe down the road who didn't have a problem with warping. So I decided to try and find Joe. I went around some small firms specializing in restoring vintage cars and asked if they knew of Joe. Two firms I tried recommended him and gave me his address.
I had four wings from a 50 year old car from which I had stripped all the paint,etc from the outer surfaces but the inside surfaces were much more difficult to clean up and I decided to take them along to Joe for blasting.

I told Joe I was very worried about the possibility of the metal warping and he assured me there would be no problem. Even so I just gave him one wing to blast first after which I inspected it. It was a rear wing with very curved surfaces and no flat portions on it. It appeared fine after blasting so I told Joe to go ahead with the remaining three.

When I got home and inspected the front wings, which were much larger than the rear, and had fair sized flat areas on them, I found that the flat areas had changed to concave viewed from the outside. Not only this but the metal, after blasting, seemed to be significantly less flexible on both the front and rear wings.

I sat down and thought about what had happened and it seems to me that the blasting is causing the area blasted to increase in area compared with the back surface which is not affected. Only one thing can happen, the metal surface bends and the surface blasted goes convex from being flat. This is not what one might expect: at first sight you might think that the surface blasted would change to concave with the force of the blasting.

Basically the metal surface blasted is stretched and in compression. So I thought how could this surface be shrunk back and the compressive strain relieved. One way I thought might be to use a shrinking disc. So I made up an 8" disc for a 9" grinder and went to it on the inside surfaces of the wings. It was amazing! As the disc was moved over the surface you could actually see the surface returning to flatness from convexity. Unfortunately, I couldn't do the whole of the inside of the wings because clearly with the shrinking disc access is limited on heavily concave surfaces.

I accept that with blasting on one side only there is more risk of curvature change but to my mind relying on the curvature induced by blasting an outside surface to exactly compensate the curvature resulting from doing the inside surface is very risky and is a recipe for producing potato crisps.

If only I had my time over again I would willingly spend weeks and weeks of time sanding the paint and rust away rather than go near a blaster.


As for rust removal, in not too severe cases I wouldn't be without phoshoric acid. Rather that spend a fortune on the commercial concoctions such as Naval Jelly/Jenolite/Hammerite rust remover/ what I did was to buy a couple of litres of concentrated (80%) phosphoric acid from Ebay. This acid is used in Hydroponics for adjusting Ph and is sometimes called 'Ph Down'. I use it diluted with water to give 20% strength and the resulting gallon or two will last you a long time even if you become as fond of it as I am. After ten minutes or so you can either 1. wash it off thoroughly in which case you might need to dry the surface quickly with a hot air blower or else the surface will rust again in the time it takes to dry naturally or 2. wipe the surface with a damp cloth without rinsing it. When dry a whitish film of iron phosphate will be left behind which offers protection for a while against further rusting.

I wouldn't worry about handling it - to my mind 20% is quite benign and I never wear gloves. I try and avoid having it on my skin for long but when it is I don't notice it. It is nowhere near as corrosive as hydrochloric,sulphuric or nitric acids.

But as for media blasting .......No,No,No,No,No ........................ Mike

[Dawai]

Down heah in Gawgia, they use talc a whole lot to blast old cars.. I saw a guy using nutshells once.. I don't know where the devil you get that many nutshells from thou?

THE soda-bath dc electric current derusting method, The paint floats off, looks like a pair of panty hose half way off a woman.. all wrinkly and stuff.. According to the post which we lost a good part of.. the hydrogen bubbles formed at the metal surface is what releases it. That and the heat generated..

SORRY ME, I used a cheap arsed epoxy primer (Kirker) on the last thing I soda washed.. It is bleeding through to the metal.. (Randy, it's your fault). The things that went ahead with paint look fine.. That's about a hundred hours of my life I lost cleaning that old truck cab.

[CARS]

My advice to anyone thinking of grit blasting car panels is No,No,No,No.... Don't do it!



But as for media blasting .......No,No,No,No,No ........................ Mike


I really have to wonder why it works for some and not for others :confused:

I guess just because someone has a welder, it doesn't make them A Welder.
Takes hours upon hours and years of practice to do it right. Then maybe you are an accomplished Welder, Detailer, Painter, or Media Blaster.

Just a thought.

[CARS]

Down heah in Gawgia, they use talc a whole lot to blast old cars.. I saw a guy using nutshells once.. I don't know where the devil you get that many nutshells from thou?



Haven't you ever bought walnuts for baking? They don't have the shell. Get every Grandma, Mom, Sister, Wife, and Daughter to make pies and BAM!! Excess walnut shells.

As far as the rest of your post... :o What are you saying David??? You lost me again :lol:

[Dawai]

http://www.bbssystem.com/manuals/Derusting_oldtruck.pdf
Lost ya huh Chris? OKAY.. here's some catch up dar... Derusting, via livestock watering tank, arm and hammer soda and dc welder current..

Used to be fun, get someone in a souped up car on my tail in some tire squealing corners.. jab on the brakes, then immediately jab on the throttle and smoke em, gain about a 1/4 mile on them, turn out the lights and let er rip.. LOSE em..
(yeah, I learned to drive in Moonshiner country)..
If all else fails, throw a beer can at them.

Grandma cracked her own nuts for the cakes. You must have growed up rich..