MgAl smells like ammonia

[asdercks]

Hi guys, a few months ago I bought some MgAl from Hunter and everything was fine until today when I opened the container and I notice an ammonia like smell, is this normal or should I be really worried?

[Mumbles]

It's not uncommon with MgAl. Normally I hear about this with homemade MgAl. It's thought to happen due to metal nitrides that get formed due to the hot metals reacting with nitrogen during it's manufacture. When nitrides react with water they produce ammonia and metal oxides. Generally I've never heard of it causing too many issues, but I agree it would be sort of off putting. It's probably just the slow build up of ammonia over several months. It probably wasn't too noticeable at first since the bag had recently been open when it was packed.

[asdercks]

Thanks for the reply mumbles, I really thought I was in a big trouble I will place a dessicant bag inside the container, may be that helps to remove some moisture and thus reduce the smell of ammonia

[WSM]

Hi guys, a few months ago I bought some MgAl from Hunter and everything was fine until today when I opened the container and I notice an ammonia like smell, is this normal or should I be really worried?

 

The first time I attempted to make MgAl, it had a strong odor of ammonia, and I reallized I had a problem. In fact, when I quenched it in water, it fizzed like soda pop and a very strong ammonia smell developed.

 

When I researched it, I realized it was the aluminum nitride (if memory serves) that created ammonia in the presence of ANY moisture, even atmospheric moisture.

 

I believe those who quench their molten MgAl (slowly and carefully) in water and fully dry it (perhaps in an oven), alleviate the problem by reacting and washing away any nitrides before they can be an issue.

 

WSM

Edited August 20, 2014 by WSM

[ddewees]

I had/have this issue too, and only recently noticed it when opening a sealed 5 gallon bucket. It had been sitting for awhile...

[rogeryermaw]

i noticed this same odor after about 3-4 days milling aluminum foil with a touch of charcoal. i found the smell very peculiar even with the known chemistry behind it as my mill jar was completely sealed. i guess a very little bit goes a long way.

[californiapyro]

For what it's worth, it smelled like ammonia from the first time I opened the packages. I store mine in a 5 gallon bucket with some dessicant packs, and the odor went away.

 

-Hunter

[ddewees]

That's what I suspected... but it has suited my purposes fine so far.

[dagabu]

That's what I suspected... but it has suited my purposes fine so far.

 

Its moisture left over from the processing I am guessing. Like Cali, I had a small lot that smelled as well and a container of silica gel did the trick to get rid of the smell.

[MWJ]

Does the quality go down if it's wet then dries out with the sil. gel.

[WSM]

Magnalium is peculiar stuff. It's not a true alloy, but an intermetallic mixture. This was seen when testing magnalium for magnesium with Magnesson reagent. The test involves dissolving the metal sample in concentrated hydrochloric acid, then neutralizing it with sodium hydroxide, which forms a flocculent precipitate of metal hydroxides. This is when the Magnesson reagent is added, dropwise, to the alkaline solution. Magnesium is indicated by bright blue coloring, where aluminum is a pinkish purple. Proper magnification is needed to spot the bright blue magnesium hydroxide flakes amongst the massive amounts of aluminum hydroxide observed.

 

It must be remembered that magnesium breaks down in an acid environment, whereas aluminum breaks down in an alkaline environment. Magnalium is a weak cross between them and ideally should be kept in a pH neutral mixture (not always easy to do). When the magnalium generates ammonia, the ammonia (being alkaline) tends to affect the aluminum part of the magnalium negatively.

 

Washing the magnalium with water and thoroughly drying it should help. I don't think a silica gel pack would hurt, as it traps any water vapor there which would tend to react with any aluminum nitride present to generate ammonia gas (NH₃), if I understand things correctly.

 

The best solution to the problem, if you make your own magnalium, is to have a slow but constant feed of an inert gas during the manufacturing process, over the metal melt to purge any atmospheric gasses (O₂ and N₂, primarily). Argon is probably the best choice since it appears to be the most abundant inert gas in our atmosphere, and should cost the least.

 

WSM

Edited October 7, 2014 by WSM

[pex]

I made a batch magnalium shimuzu glitter yesterday. And they smell a bit like rotten eggs. The magnalium smelt a bit like amonia to. They didnt heat up. Is this a big problem? I didnt noticed the amonia smell after the stars start to smell like rotten eggs.

[Mumbles]

Which Shimizu glitter did you use? There are only a few listed in FAST, and they're actually from Winokur and all aluminum based. I don't have Pyrotechnica XIV handy right now to look at what he discussed there.

 

Experiencing a rotten egg odor or ammonia from MgAl compositions is never good. I've gotten it a little bit while trying to force dry them in a drying chamber. This almost always killed the star effect. A little bit of an odor under normal conditions isn't usually too much to worry about, and sometimes normal, but I usually do my best to try to prevent it. It's annoying at best, and a sign of impending issues at worst. For MgAl, that would generally mean using dichromate water or dichromate in the composition. A strong odor is usually a bad sign.

[pex]

http://www.pyrodb.org/composition.php5/407

 

This composition.

 

Than i start cleaning my magnalium to