Brimabright media blasting ?

[LH Drive]

I've been removing the paint off my rover with paint stripper. It's a slow process as it wears three coats of paint. Hardest to remove has been the original paint coating. Considering having the aluminum 88" bed/tub media blasted down to bare metal inside, outside and underneath. Found a local shop that specializes in aluminum media blasting. They use all new media and will be using a glass bead media on the inside where the aluminum is a thicker gauge. The outer thinner panels will get blasted with soda media to reduce any chance of warping.
Anyone used soda blasting on brimabright before?

[Pete]

I recently had a mobil unit come to my house and blast for me. He used soda on all the aluminum panels and it came out awesome. It didn't heat the panels up so there was no warping and the media is so soft that is doesn't hurt the aluminum.
If they can shoot soda, I would have them use only soda no matter how thick the aluminum may seem. As good as soda works on paint removal, there is no need to shoot glass.

Pete

[o2batsea]

You will remove the protective chemical skin that was applied at the factory if you have it blasted. There's no need to take all the paint off if you are just going to paint it again. A thorough and meticulous sanding followed by two coats of epoxy primer (also sanded with 220) followed by 2 part polyurethane topcoat will give you a smooth extremely durable finish.
If you really really want all the paint off in the least destructive manner you should have it dipped. You will have to take the steel supports off since the chemical stripper for aluminum is not compatible with steel.

[LH Drive]

I recently had a mobil unit come to my house and blast for me. He used soda on all the aluminum panels and it came out awesome. It didn't heat the panels up so there was no warping and the media is so soft that is doesn't hurt the aluminum.
If they can shoot soda, I would have them use only soda no matter how thick the aluminum may seem. As good as soda works on paint removal, there is no need to shoot glass.

Pete

It would be faster if glass bead was used for the inside of tub. Will have a small area glass basted to see if it doesn't rough up the aluminum too much.

[TeriAnn]

You will remove the protective chemical skin that was applied at the factory if you have it blasted. There's no need to take all the paint off if you are just going to paint it again.

Agreed. With today's paints you will not get as good a primer as what the factory put on new and the chemical skin underneath provides corrosion protection. Unless you have a LOT of $$$ to spend you are best off sanding off any post factory paint then sand it smooth for a new primer coat. The more factory primer still there the better to protect the metal.

If you have a lot of money to spend take it down to an aircraft painter and get the full treatment for an aluminum skinned plane. Or for a little less money if you have a willing college with an A&P curriculum see if you can get the students to paint it as part of their airframe training.

[superstator]

You will remove the protective chemical skin that was applied at the factory if you have it blasted.

Do you have some details on this chemical treatment? I would have thought the natural aluminum oxide would be the best "protectant" you could ask for...

[superstator]

Answered my own question:

conversion coating

Sounds like it's basically chemically accelerating the formation of aluminum oxide. I have a hard time believing soda blasting would take off the oxide - that stuff is a challenge to get off with a wire wheel, or at least that was my experience when trying to learn alu TIG welding.

Also interesting: http://www.crankshaftcoalition.com/wiki/Soda_blasting

[o2batsea]

I hope you mean a stainless steel wire wheel. Using a plain steel wire wheel on aluminum is about the worst thing you can do.

[superstator]

I was just taking the oxide off scrap aluminum to do stringers - I wouldn't use either for bodywork obviously... Point was just that the oxide is hard stuff, and I'd be impressed if soda could really make it budge. But I may also be betraying my ignorance.

[JackIIA]

TeriAnn - what about non-compatability of paint 'systems'. I'm always reading how you need to ensure primer "a" will work with finish coat "b", which must work with clear coat "c". Even if you're using an expoxy primer of some sort to seal everything, how can you be sure it won't bubble etc??

I figured when you see guys doing overpainting, they know what was on there already. Is this just paint company propaganda?

[thixon]

LH Drive,

Your plan will work fine. Make sure the guy you hire has blasted thin aluminum sheet before, just to make sure he understands what can happen if he holds his nozzle to close for to long when blasting with the glass beads. Soda blasting is a decent enough process, and it will remove the paint. However, if their blasting off three coats of old paint it'll take time and lots of soda to get it all off. Make sure you make them aware of this and agree on a price BEFORE they begin. Otherwise, they're likely to try to up the price on you for the extra soda and time.

The other thing to consider is cleaning it afterwards (Same is true of a chem strip). Get all the soda out of every nook and cranny before it goes to the shop.

The comments from others about not stripping down to bare metal are okay suggestions. However, since you have multiple layers of paint, I'd be apprehensive to paint over them again if you're after a quality finish that will last. If there's an adhesion issue with one of the old layers, you're new paint job won't be worth squat.

Not sure why others who commented are concerned about the "chemical skin" or the quality of today's primers. Today's paint/primer systems are far superior to what was around when your truck rolled off the line, and a good epoxy primer will stick like glue to your bare body panels.

[o2batsea]

Not sure why others who commented are concerned about the "chemical skin" or the quality of today's primers.

It's Aluminum 101 my friend!

Back in the day when they were making the Birmabright panels for your friendly Rover, they went thru a fairly intensive process the avoid the formation of an oxide layer on the aluminum panels. The alloy was rolled, cleaned, dipped in different chemical baths and finally formed into the shapes so familiar to us before being painted. This is only one of the reasons why they cost twice as much as a similarly kitted out Jeep. With the oxidation prevention methods they used we find that forty, fifty, years on despite being thrashed, the Rover bodies have held up pretty well all in all.
If they had just used the alloy straight up without the preliminaries, the aluminum would be in far worse shape by now and we'd all be in a pickle trying to repair un-Birmabright. Thankfully we ain't.

So, the dealio is that taking off the micro molecular layer of protection will leave it, well unprotected. Five minutes after it has been blasted there will be a couple-of-molucules thick layer of aluminum oxide on the panels that you cannot see, but will nonetheless begin a process that will never end until the entire panel has been consumed. Sure, that may take several hundred years, but hey, what about the Rover fanatics in the twenty-fifth century? They need some love too! Anyway you see what I mean. There's no way you can blast the Birmabright without starting it oxidizing. You should really do an Alodine wash to bring it back to protected mode before applying primer.

Just cuz that idiot on the Velocity channel soda blasts 500K Ferraris doesn't mean it's the right way to remove the old finish. He's trying to make a buck, not restore a car.

I had the body parts on the 109 stripped at a shop that does this sort of thing. They actually dunk the whole tub and roof and all in a giant tank. It took off every speck of paint and gook but left the original white coating on the metal. The guy was all apologetic that it didn't come off down to the bright aluminum. After giving him the short version of the above explanation he was relieved that I wasn't unhappy.

[I Leak Oil]

Oh my God my head is about to explode....strip it by blasting or chemicals, prime it with something appropriate for aluminum and top coat the damn thing. This isn't rocket science.

And the layer of aluminum oxide IS what protects aluminum and keeps it from oxidizing into a pile of metal dust! This same layer of aluminum oxide is what makes it difficult for primer and paint to stick to it. Prep it properly and your all set.....Move on already.

[thixon]

X2 i leak oil.

O2batsea,
Maybe you should just stop posting responses to the things i post about.

Lhdrive, go ahead with your plan. It'll be just fine. If you have any questions, feel free to pm me.

[o2batsea]

That's a great idea. I waste enough time on your duff ais already.