Oh, No! I got rusty balls!

[FlareLauncher]

A friend just gave me a bunch of steel balls, I want to use in my ball mill. I am making different mill for different classes of chemicals that I can use on the same motor platform. The balls should be great for aluminum, but they're rusty. I don't really want to donate oxides to my AL as I grind it. Should I ball mill some sand to clean them, or is there a better idea? Thanks!

[pyroman2498]

May I ask why you would mill Al , that's dangerous and shouldn't be done unless you are fully aware that you are putting your life in danger when you open that lid and pour out the contents .

 

It depends how rust the balls are to Rome the rust, but using anything that can spark with flammable Al is not smart at all , your a just asking for trouble .

 

Stay Safe and Stay Green

 

~Steven

Edited June 5, 2014 by pyroman2498

[FlareLauncher]

I'm aware of the danger, thanks. Planning on very small batches, I have no need for AL in quantity. Learning this phase as I have every other one I have attempted. No problem with staying very small. I just need the steel balls clean before I start.

[pyroman2498]

Quantity isn't the problem here , it's 2 things , grinding Al , and the biggest worry , grinding it with Steel , a sparking material , that will catch the Al on fire and cause burns to you.

I don't see this going well if you do it....

 

Stay Safe and Stay Green

 

~Steven

[schroedinger]

Just for cleaning the rust if, i would first try to polish them using sand like you suggested.

But for the aluminiu if you really want to use those steel balls, make sure to add a inert atmosphere or better use the wet process (but better go with non spark medium)

[BurritoBandito]

Do NOT backfill the jar with an inert gas! I'm not sure of that's what schroedinger was suggesting, but you want the aluminum to oxidize in the jar. Failure to provide enough oxygen can result in the aluminum becoming pyrophoric. When you open the jar it will ignite. If you do decide to mill aluminum make sure that you periodically open the jar to allow air in. The frequency at which you'll need to do so will be dependent on the efficiency of your mill, but I'd say for any reasonable hobbyist sized mill every 4 hours is often enough (please, someone correct me if this is wrong?).

 

You may also want to check out this thread for more ideas of removing the rust from your balls http://www.amateurpyro.com/forums/topic/9660-cleaning-iron-filings/.

 

Edit: I thought steel was idea for milling aluminum. Is there really a risk of ignition from a spark the jar? Especially since the oxygen is likely to be low from the aluminum forming a passivation layer. This is not a sardonic remark, but a legitimate question. Thanks.

Edited June 5, 2014 by BurritoBandito

[FlaMtnBkr]

Just mill some other things and it will clean them up. No one wants dirty balls. Sand might work, but charcoal works pretty good. Just give it a try and if it doesn't work, try longer. If it still doesn't work, change the material you are milling.

 

While small batches can be good for safety, they aren't always good for your milling material. If the mill isn't charged optimally, you can get excessive wear on your milling material. The material you are milling helps isolate the media from each other and reduce wear.

 

I would use an extension cord and barricade your mill in case there is an accident. Then crack the lid, let a little air in, poor the lid on and get away. Do this a couple times so the metal can slowly oxidize.

 

And you might just be better off buying a pound of aluminum. It probably ends up being about the same price when you factor in materials, time, and electricity.

[pyroman2498]

Edit: I thought steel was idea for milling aluminum. Is there really a risk of ignition from a spark the jar? Especially since the oxygen is likely to be low from the aluminum forming a passivation layer. This is not a sardonic remark, but a legitimate question. Thanks.

Well think about it for a second , if your milling with a sparking media and you get that Al to a fine powder, I see a fire happening , and when you open the jar you let in oxygen and when you start the mill fresh oxygen is introduced so there is all the combinations for a fire, Idk about you but I wouldn't risk my life for a batch of Al, but this is just my opinion.

Why not buy a pound or a few pounds of Al , cheaper and safer .

That's just my 2 cents

 

Stay Safe and Stay Green

 

~Steven

[BurritoBandito]

So what media would you suggest using?

 

Edit: I did a search to try and find an answer to this question and this is what I came up with.

 

 

Ball milling it somewhat could certainly break it down. Maybe an hour at a time. Stainless media is ideal. I wouldn't try to get it too fine. Fine flake Al and atomized is too cheap to really worry about it. What you have could be interesting in comets, fountains, and waterfalls..

http://www.amateurpyro.com/forums/topic/3766-turning-turnings-into-usable-material/?hl=%2Bmilling+%2Baluminum&do=findComment&comment=52080

 

No disrespect Pyroman2498, but I'm inclined to agree with Mumbles here. I do agree that it's easy just to buy it, and you will wind up with a much better quality product.

Edited June 6, 2014 by BurritoBandito

[LiamPyro]

I had the same problem, so I tossed a handful of sawdust in the mill jar with the media and ran it for a while. When I checked the balls they were rust-free and only speckled with little dimmer areas. I don't know how rusty you're media is, but mine was'nt that bad and they were clean within several hours. If your's is really rusty you might need to mill for a few days or a week. One advantage of using sawdust is that it will absorb any moisture in the mill jar or on the balls!

[FlareLauncher]

Jeez, everybody - about 99.9% excellent advice.

No to the inert gasses, yes to a little charcoal in the mix.

Good ideas for cleaning the balls, I think sand first, then sawdust. I'm a hobbyist and in no hurry. As I learn along the way its all good. My understanding is that steel was preferred to lead as it will crush it more finely. As to sparking - steel needs something to spark against, yes? Steel balls in a small ball mill cannot spark as I understand it. Honestly. I'm glad the other areas I have ventured into have not been so complicated and dramatic. Thanks, All for the good input thus far. I appreciate it.

[BurritoBandito]

I don't doubt that steel balls in a mill can spark for a second. I do have my doubts that the spark would do much in the case of aluminum. I definitely would never mill BP using steel.

[FlareLauncher]

I have lead balls in another mill for my BP. I believe that lead is not optimal for AL.

[schroedinger]

Sry, maybe i didn't make it clear enough what i wanted to say (i really didn't reading my post and your suggestions). The inert gas was just meant to be used if he really wanted to use the sparking steel balls introducing the oxigen stepwise by opening the mill every couple hours.

 

Flarelauncher of course the steel balls can spark in a mill (steel against steel). The steel balls which some people use for making bp are all nonsparking steel grades those won't spark.

[krakra]

Just submerge them into enough solution of oxalic acid. It cleans all kinds of rust like wonder. Other rust cleaners should work fine too, many of them contain oxalic acid or similar chelate agents.

[Mumbles]

Lead is likely too soft for aluminum, this is true. Generally, when steel is used as a milling media, it's non-sparking versions of stainless steel. Lead would also be subject to the issue I'm about to mention.

 

The other thing I'd be concerned about is creating a small thermite type reaction. As it was mentioned earlier, rust would love to give up it's oxygen to aluminum. The reaction can definitely be initiated mechanically. There are neat demos you can do by taking two rusty shotputs or large bearings, and covering one with aluminum foil. When you strike them together, a very impressive, short lived thermite reaction takes place. There's a snap and sparks and some light.

[BurritoBandito]

Hmm... I'm going to have to try and find a way to set up one of those demos. That sounds like it could be kinda cool to watch. What would you expect if you shot a severely oxidized piece of copper at a thick aluminum plate?

[MrB]

Late to the show. I would add my voice to those stating that using rust-balls for alu milling would be a bad idea.

Cleaning the balls should make them safe enough, and i think i would do that with kitty litter. Bentonite doesn't really suffer from the added ironoxide content, and should be abrasive enough to make the balls look like new.

 

Ideally spark-resistant stainless steel should be used, but given that "most" by their milling media from second hand sources, like eBay, it's hard to tell what your really getting. Just know that alu milled with "soft" steel will have a tiny bit of steel in it. This may or may not be an issue... Doubt it, but worth remembering.

B!

[BurritoBandito]

Yeah, I think the general consensus was that steel is a good media, but only non-sparking grades. I personally would not use those particular steel balls for milling aluminum, because of it's unknown qualities. Knowing that it can rust would make me a bit sketchy about using them. I doubt that there is any risk of serious harm from milling straight aluminum with sparking media, due to it being a fuel only, but any accidents which we can try to avoid, we should.

 

Not to contradict my previous statement, but I also feel that risk assessment is important, and would be interested in knowing more about the potential risks involved in using a sparking media. Obviously the more oxygen in the jar, the more the aluminum can burn. Once te structure of the jar has been compromised there will be plenty of oxygen to sustain combustion. But, how likely is it that a properly loaded jar would contain enough oxygen for this to happen, and also how likely is a single spark to actually light any aluminum particles of a size obtainable in a hobbyist sized mill? According to this site the melting point of stainless steel is twice that of aluminum, so I'd assume the steel spark is hot enough. Any more informed opinions would be appreciated.

[Shadowcat1969]

BB,

My understanding (and may be incorrect) is that the issue with milling aluminum is not having oxygen in the jar as it is milling, but exactly the oposite. It is that, during milling the freshly exposed faces of aluminum are using the oxygen in the jar to oxidize, but with a relatively "slow" rate. Once the oxygen in the jar has all been "used" to create a layer of aluminum oxide on the surface of the aluminum particles, if the milling continues, you then have an ever increasing surface area of pure aluminum. Once a mill jar is opened, the addition of oxygen from the opening of the jar allows the aluminum to oxidize again. If enough surface area has been exposed due to long milling in an inert atmosphere, the resulting oxidation reaction is so much, so fast, that it then ignites the aluminum. No spark source is needed.

 

That being said, myself, I would not want to use any media that could generate a spark for any milling that we do in pyro. Just to be as safe as possible.

[FrankRizzo]

Hmm... I'm going to have to try and find a way to set up one of those demos. That sounds like it could be kinda cool to watch. What would you expect if you shot a severely oxidized piece of copper at a thick aluminum plate?