[Mike 1948]

FYI,
I have a CNC set up with a homemade water "pan" to catch the majority of the black soot and dross from cutting my artsy type steel stuff. Well, I had to cut several sheets of artsy stuff out of 1/8 aluminum sheet last week. Everthing went fine got the projects cut, shut everything down and walked out the door to the shop.
A week later I get back to the shop and the carbon monoxide detector alarm is going off. No gas apliances are on so I blew it off as glitch in detector, UNTILL I walk over to the area were my plasma machine is. The water pan is bubbling, not a boil but quite a bit of bubbles. I opened the doors and aired out the shop. We took the pan outside and for a test put some dish detergent on the top of the water. We waited till there were quite few bubbles and put a match to them, foooff, minature little Hindenburg explosion. HYDROGEN gas.
I'm no chemical engineer, was this from the combination of steel and aluminum dross in the water? Would a clean pan of just aluminum dross also start this reaction in water? Is there a real danger of a major explosion? Or just a little one !
I don't know if anyone has seen this before but it looks like I have some cleanup to after cutting aluminum.

Mike

[Geof]

There is indeed a real danger of explosion if the room is well sealed so there is no air circulation to dissipate the hydrogen. This may not be likely but the consequences could be a bit serious.

You are getting a reaction between the iron and aluminum in the water, iron oxide (rust) can catalyse the oxidation of aluminum. Actually a possibly bigger risk than a hydrogen explosion is a thermite reaction. This is a high temperature reaction between iron oxide and aluminum which releases large amounts of heat. In the presence of water it can create a steam explosion.

Keeping the pan clean is probably a good idea. Aluminum by itself in water, water at neutral pH that is, is okay. Aluminum in the presence of alkali such as some detergents and many anti-corrosion additives may produce hydrogen gas but not very much unless it is strongly alkaline.


EDIT:

I decided to see what I could find, have a look at this and scroll down to the second page: http://www.alcoa.com/global/en/envir...oadMSDS=172320

[Mike 1948]

There is indeed a real danger of explosion if the room is well sealed so there is no air circulation to dissipate the hydrogen. This may not be likely but the consequences could be a bit serious.

You are getting a reaction between the iron and aluminum in the water, iron oxide (rust) can catalyse the oxidation of aluminum. Actually a possibly bigger risk than a hydrogen explosion is a thermite reaction. This is a high temperature reaction between iron oxide and aluminum which releases large amounts of heat. In the presence of water it can create a steam explosion.

Keeping the pan clean is probably a good idea. Aluminum by itself in water, water at neutral pH that is, is okay. Aluminum in the presence of alkali such as some detergents and many anti-corrosion additives may produce hydrogen gas but not very much unless it is strongly alkaline.


EDIT:

I decided to see what I could find, have a look at this and scroll down to the second page: http://www.alcoa.com/global/en/envir...oadMSDS=172320

Thanks for the info. Looks like I better not be mixing my materials without cleaning the water pan. The Iron oxide rust mixing with the aluinum dross seems to be the culprit. The article does say that while plasma cutting, the small drops of aluminum do not create a fire hazrard themselfs, they can create hydrogen apparently when they hit the water. It says to vigorously circulate the water.
I guess I will have to do some redesign to my water pan or give up the aluminum.

Thanks Again
Mike