Painting The Inside.

[rna_duelers]

With my hybrid that is currently be constructed I have a few issues I need to figure out,and one of them is with the material being used.The chamber is made from Aluminium and I plan to use oxidisers and and many atmosphere shots,the trouble being that some people have had issues with oxides forming on the chamber walls with Aluminium so I plan to paint or coat it some how to prevent the chamber from oxidising.So anyone with some good easy ideas on how to paint the inside of the chamber please fire them off in my direction.

I did have one plan of using an engine enamel and filling the chamber with a lot of the enamel and rolling it around back and forth to coat all walls but I am unsure about how well it will coat the walls,so any ideas would be great.

[psycix]

Maybe you can use some sort of car wax/paint stuffto prevent the oxidizing.

[dwats32]

Degrease the aluminium first then sandpaper it to prepare to for painting. You'll have to do a bit more than that if you want a really good finish by using powder coating

[rna_duelers]

I cannot get my hand in the chamber the hole is only 40mm,chemically cleaning can be done though.

Powder coating...I'm not made of money.But the problem with using a wax etc would be burnt by the combustion would it not?

[dwats32]

Engine enamel sounds fine.

[MrCrowley]

Sand paper it by putting some sand paper on a long stick that is similar diameter so it fits inside well.

[rna_duelers]

The chamber is a liquid oxygen bottle so the shape isn't to sanding friendly.Do you think that just degreasing it would be fine or would the sanding be needed?

[MrCrowley]

Fill it up with sand and make it into a sand cloud gun, but that requires you drilling a hole in the chamber and I doubt it would even work

I say try the enamel idea.

[rna_duelers]

Hahahah any bet my gun has a high ROF then yours....It's in the millions of rounds a second with sand .

Enamel it is!

[Marco321]

Do you really need to prevent it from oxidizing? Aluminum is called a passivating metal, which means the oxide it forms protects it from any further corrosion, so its kinda natures way of making a protective barrier on aluminum.

Thats why aluminum is often used in those outboard motor tubby boats, is oxidizes, which makes a protective layer, preventing further corrision.

[SpudBlaster15]

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

[jimmy101]

Marco321 and Spudblaster are right.

Only a couple minor points. Aluminum oxide is indeed very hard but it adheres to the aluminum pretty poorly. Much better than iron oxide adheres to iron but still pretty poorly. If you take a hunk of aluminum you can use it as a pencil, transfering a gray line of aluminum oxide to a piece of paper. Once the oxide layer is worn off it quits writing. Let it sit for a few days and the layer will reform and it'll write again.

Anodized aluminum is oxidized aluminum that has been carefully treated to maximize the adhesion of the oxide layer to the Al. The anodization coating is pretty strong but smack it with something hard and it will chip off.

I would say that, as long as you are filling the chamber with gases, then the oxide layer that forms just form air exposure will be adequate. If you are doing anything that makes mechanical contact with the oxide layer (like filling with liquid and shaking) then the layer will flake off. This may or may not be a problem since the layer will reform pretty quickly.

The big concern would be exactly what you mean by "oxidizer". Air is fine. Compressed air is fine. Pure oxygen might be another thing. Compressed pure oxygen is definetly another thing, especially at very high pressures. Any stronger oxidizer (hyrogen peroxide etc.) greatly increases the risk that the aluminum will be attacked regardless of the oxide layer.

Of course, strong oxidzers will also attack most paints, so even painting the surface might not protect it.

So, whatever you are up to, be careful.

[psycix]

The chamber is a liquid oxygen bottle so the shape isn't to sanding friendly.Do you think that just degreasing it would be fine or would the sanding be needed?

A liquid oxygen bottle?!
Dont you think it can withstand oxidizers then?
Maybe there is already a coating inside.

[DYI]

A lot of liquid oxygen cylinders only have an operating pressure of about 25psi, not nearly as high as gaseous oxygen cylinders. However, the cylinder is designed to hold pressurised oxygen in the first place, so I fail to see what the problem is. I would hope that you aren't planning on using concentrated H2O2, because that would just be asking for trouble.

[rna_duelers]

I was thinking the same thing about the oxide layer forming on the inside and making a protective coating.

And it is a liquid oxygen bottle...DAHHHHHHH I'm such an idiot of course it's going to have a protective coating on the inside,why didn't I think of that before...I will how ever paint the other Aluminium fittings and sections that are going to be exposed to oxidisers.

No H202 going to be used but there is going to be 02 and N20 with propane and MAPP etc,it's going to be fun.

Thanks guys.