MgAl Shelf Life

[nordicwolf]

I read in another post that crackle over time can go bad because the Magnalium degrades.

 

How long can MgAl last before becoming useless or at least less effective?

 

Is there anything that can be done to increase the shelf life?

 

I bought some 2+ years ago but have not used it much, and I also bought some from another pyro getting out of the hobby - unsure how old it is.

 

Will silica dessicant packs in the MgAl baggies help extend the useful life?

 

Thank you.

[a_bab]

Finely milled magnalium is far more prone to degradation than the course variety.
This is due to the magnesium that slowly turns to nitride with the nitrogen in the air (this causes the dark magnesium color).
The nitride further hydrolizes with the water in the air giving ammonia. It also oxidizes and you end up with a nonreactive mix.

The metallic stars that use magnalium as fuel are generally parlon-based meaning there is some protection from parlon.
Plus, they are bound with organic solvents, without water. So you end up with a rubber matrix basically.

My crackle stars were bismuth-based, and even if I bound them with NC, while they popped amazingly when I made them, they were far less impressive a few years after. And they were stored dry.

We have the same issue with strobe rockets; they don't store well for the same reason. They are best used within weeks from manufacture.

Yes, silica helps. If your magnalium looks shiny and sparkly, good for xmas decorations, then it's still good

Edited November 29, 2022 by a_bab

[WSM]

If you are able to, and willing to make your own magnalium; if it is cast into ingots which are stored until needed, would be the best way to keep it "fresh".

 

If you grind only enough MgAl (from the ingots) for use within six months of grinding, you would always have fresh material, since the degradation would only be on the surface of the ingots.

 

A thought I had years ago but never put into practice due to not having built a forge/furnace capable of smelting aluminum yet. One day I hope to but too many other projects will happen first!

 

WSM

[taiwanluthiers]

I found out an acetylene torch will happily melt aluminum, but really a propane torch with fire bricks as insulation will work. This is how they cast aluminum.

[kingkama]

I found out an acetylene torch will happily melt aluminum, but really a propane torch with fire bricks as insulation will work. This is how they cast aluminum.

Also a brick furnace coal fired and blow air with a hair dryer can do it

[DirtSlayer]

I have to post something to be able to download files. But I am also curious, has anyone attempted to make magnalium in a safe enough manner?

[kingkama]

I have to post something to be able to download files. But I am also curious, has anyone attempted to make magnalium in a safe enough manner?

I used this method, first weigh and melt the aluminum, pour it in water to reduce it to small drops, weigh the necessary aluminum again and remelt it, when it is hot enough To emit a reddish light, add lumps of magnesium and a large lump of charcoal, so that there is no oxygen available, mix well and cover the crucible with a lid so that there is As little oxygen as possible, a tall, narrow crucible is ideal. I also tried to use scrap magnesium from turning but being in fragments makes it easier for it to catch fire. As soon as the alloy has melted, it must be poured into water so that it cracks as it cools quickly. I have noticed, as many have said, that magal cast in water is less sensitive and less reactive to humidity. Melting mgal can be risky so it's best to start small and have a bucket of sand nearby.

[cmjlab]

There's a tutorial floating around that many have used (including myself). I recently made several batches to make 20 lbs of Mg/Al. I've not used the method outlined above, but have made several batches in the following manner:

 

Safety Equipment: **Face Protection (Eyes are NOT replaceable!** Thick Leather gloves, preferably long ones to protect wrist and forearms. Jeans or equivalent. Full covering boots. Long Sleeves. Bucket of sand to control fire should it happen (don't use water).

 

***Edit / Note: You can use air float charcoal to control flare ups on the surface of your Mg/Al melt in the crucible. For example if you remove the lid to add more Mg, and it lights up, sprinkle a spoonful of charcoal on and it will help extinguish it. Once you stirred the final melt, and if you plan to let it cool in the crucible, sprinkle a couple large spoonfuls of charcoal on top, and it will prevent it from catching fire if oxygen makes it in the crucible.***

 

1. You need a charcoal starter or some other means of creating a container of lit charcoal, that has blown air, in order to get a high enough temperature to melt Al. (There are several YouTube tutorials on this). You need a steel stir stuck to mix Al and Mg melt right before it's done to make sure it's completely mixed together.

 

2. You need a source of Al and Mg (chunks, NOT powder / shavings / filings, as they are likely to burn, NOT melt.) Al is easy to find (but is not always pure, so if you know the alloy you can account for that percentage of another metal when adding up to 50/50 Al and Mg). Magnesium is not as easy to find cheaply. I buy "boat anode" online and can get 5 or 10 lb anodes for a reasonable price. If you don't know the Al alloy to calculate the 50:50 ratio, just use a few extra percent Mg to account for the unknown. Worst case, you go to break up your Mg/Al but can't because it isn't close enough to 50/50 because there is not enough Mg in it, then you can just re-melt and add more Mg.

 

3. You will need a crucible. Most people recommend a stainless steel drink mixer with lid, or an actual graphite crucible (more expensive / can still burn through). The biggest issue is the possible Mg/Al melt igniting and burning through the crucible. Depending on the furnace you use, you may or may not be able to recover it if a burn through occurs. I recommend the stainless steel drink mixer, it lasts multiple melts if you are careful to prevent the melt from igniting.

 

4. You need your Al and Mg in pieces small enough to fit in the crucible (1/2" thick, up to 2/2.5" wide and several inches long works good - but really the size is not overly important as long as it's not shavings or powder). The Mg is better in chunks big enough to fit in the crucible, but not stuck out the top, so you can keep a lid on as tightly sealed as possible to keep out as much oxygen as possible.

 

5. Weigh your materials for 50:50 (Al:Mg). I did around 2-3 pound batches. But remember the larger your melt, the more dangerous, and the more likely of "burn through" (because it takes longer for the Mg to melt, the longer the Mg sticks out of the liquid Al the more it's exposed to oxygen, the more likely it will cause a flare up, and flare-ups can melt through the side of the crucible).

 

6. The "Melt" (most danger is this part). Get your charcoal and crucible red hot (you can add Al while it heats up). Melt Al first. Once Al is all melted, then you are ready to add Mg.

 

7. (** Keeping the crucible covered once Mg is added is key to preventing flare-ups / melt through the crucible, except for a quick look or to add more Mg**). Add Mg to Al a couple chunks at a time (as many that for and are still touching liquid Al, the more the Mg is in Al, the quicker it will melt and the less likely the Mg will catch fire) and put the lid back on your crucible. The lid keeps much of the oxygen out and cuts down on flare ups. Continue till all of your Mg is added. Do a final stir once it's all melted (your stir stuck will flare up when you pull it out, so don't be surprised, and stick it bucket of sand.

 

8. Finishing. This is where most people vary their process.

 

a. Some pull the covered crucible out of the furnace and allow it to cool overnight or 12 hours, then dump it out in an "ingot". It can be broken up by hammer / sack, etc. at a later time. This results in a brittle Mg/Al that's nice and shiny, with sharp shards and does not mill as quickly (milling is another, MUCH more *dangerous* operation).

 

b. Other people (myself included), pour the Mg/Al melt into a large bucket of water, with a stainless steel bowl at the bottom to prevent melt through. The benefit to this step is it creates popcorn sized pieces of Mg/Al that break down very easily (can be crushed in your hands, but will likely cut you many times since it is still sharp). Because it's so fragile, it can be processed to the appropriate size by a few different methods. (**If you pour liquid Mg/Al into water, it is a very volent reaction with some flare ups, and should NOT be done unless you have some way to shield yourself from boiling water / steam / potential explosion of water and liquid metal. - I have been using a piece of 1/2" plywood with a slot for the long handle of the crucible that allows me to stand behind it completely shielded, except my gloves hands)/. It seems like overkill, but I've not been splashed or hurt that way.)

 

Anyways, that's the way I make it. Let me know if you have questions.

 

**This is not my method, I do not take credit for the method / process*** again, there is a good tutorial floating around on this forum if you search for it.

Edited February 20, 2023 by cmjlab

[Chillardbee]

The metal powders I made back in the day (2009) I made in volume so I would have a life time supply. After 15 years, I'm still drawing from that batch and it's still just as fresh as the day I made it. The way I've kept it fresh was I keep them in canning jars (size not important but I chose 500ml so that when I open a jar, I'll be able to use it up in a reasonable amount of time.

  The trick to keeping it fresh was to heat the oven to 250f then turn it off and set the jars in the oven with the rings of the jars on semi loosely (the way you would when canning veggies) and leave them in the closed oven for 15 minutes. afterwards. I took them out and snugged up the lids and let them cool. you'll hear the lids ping as an impressive negative pressure is formed, so much so that you'll need a bottle cap opener to pry the lids off.

  alternatively, you could use the the jar adapter to a vacuum sealer machine or a vac chamber.

Even my magnesium powder has withstood the test of time under this packaging. I still have several liters of yet to crack open.

[Richtee]

Do some jalapeños while yer at it. Add carrot, celery and onion!

 

[cmjlab]

How big were your mason jars and how long did that take!  If I tried that with a lifetime supply of metals my wife would kill me, and I would have to spend a fortune on canning jars.  To be honest I would have thought, keeping a large enough sack of milled M/Al would keep the inner parts fresh if at least somewhat sealed against the elements.  I can't argue with you about it, and have no reason to doubt you!  So instead I'll be impressed at your dedication!  

[Chillardbee]

4 hours ago, cmjlab said:

How big were your mason jars and how long did that take!  If I tried that with a lifetime supply of metals my wife would kill me, and I would have to spend a fortune on canning jars.  To be honest I would have thought, keeping a large enough sack of milled M/Al would keep the inner parts fresh if at least somewhat sealed against the elements.  I can't argue with you about it, and have no reason to doubt you!  So instead I'll be impressed at your dedication!  

500ml jars. holds about 200 to 250 grams. Now a days a case of 12 jars here in Canada costs about $19 CAD but back then they were $7 or so. I only dabble in the pyro hobby. our big "celebration" comes at Halloween, a lot more fireworks at that time. Canada day would be the next big one like the US july 4th but after years of fighting BC wild fires, there pretty much a perpetual fire ban from May to September... can't say I blame them. A wild fire came to about a mile away from taking out our home in 2021, that fire was caused by lighting but still burnt 66,000 hectors in the flat lake area.