Shop safety. Could have been bad. Ferric Chloride and aluminum

R

rwn2000

Joined
Jan 6, 2003
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I had an incident in the shop last night that could have been bad. I should have stopped about an hour sooner after a good 4 day weekend spent mostly in the shop, but I just had to keep going. I had been machining aluminum for a non-knife project and had tossed a bunch of metal shavings from the mill in the big trash can. I was touching up the etching on a knife I had finished earlier and spilt ferric choride on the workbench (full strength Radio Shack etchant). The trash can was close by so I raked the spilt FC into the trash can. Bad idea. I dont know exactly what chemical reaction took place between the aluminum and the ferric chloride but it was DEFINITELY an exothermic reaction. You could here it sizzling for 30 seconds or so. It there had been more combustibles than there were in the trash can, I am sure it would have started a fire. I drug the trash can outside away from anything important and checked it hourly until bedtime and it was fine. I know aluminum isnt a normal knife making material, but we all have other projects besides knives. Just thought I would share so someone else doesnt do the same thing.

Randy
 
You were getting hydrogen gas produced by the (correctly ID'd) exothermic reaction of the hydrochloric acid (the active acid in FeCl) and the metal, in this case the aluminum. If enough heat is generated by the reaction and the LEL (lower explosive limit) of the hydrogen gas mix in air is reached... boom. (Well, more whoosh than boom in this case probably.) The other side left behind is Aluminum Chloride just FYI. In a decent quantity this is very dangerous/explosive, etc.... The fumes are also acidic and very bad for you. The old aluminum foil and drano bomb is basically this chemistry experiment put to delinquent use...
This is just one of the fun chemistry experiments I get to play with all the time thanks to our local tweaker friends (as part of the regional active lab enforcement team, not a customer :))
 
On a side note (I know its addressed here, but never enough IMHO):
Please please please wear proper respiratory gear with this stuff guys. I have lost a decent fraction of my lung capacity to the same off-gassed compounds we see in our shops. Albeit mine was unavoidable at the time, take my word for it that one lung-full is all it takes.
 
This sort of thing is why I've adopted a minimum of 1/2 hour of clean-up / list writing . note making time at the end of a shop session.

It gives me time to notice this sort of thing before I shut the door and walk away.
 
12345678910 said:
This sort of thing is why I've adopted a minimum of 1/2 hour of clean-up / list writing . note making time at the end of a shop session.

It gives me time to notice this sort of thing before I shut the door and walk away.
Click to expand...
that is a very good idea and I may need to start doing the same thing

LucyCustomKnives said:
You were getting hydrogen gas produced by the (correctly ID'd) exothermic reaction of the hydrochloric acid (the active acid in FeCl) and the metal, in this case the aluminum. If enough heat is generated by the reaction and the LEL (lower explosive limit) of the hydrogen gas mix in air is reached... boom. (Well, more whoosh than boom in this case probably.) )
Click to expand...

High School chemistry, 2 semesters college chemistry, one semester thermodynamics and about all I remember after 25 years is the difference between exothermic and endothermic reactions. :)
 
rwn2000 said:
High School chemistry, 2 semesters college chemistry, one semester thermodynamics and about all I remember after 25 years is the difference between exothermic and endothermic reactions. :)
Click to expand...

Of the things to remember, that's a good one!
 
Funny that this thread pops up.

Last weekend I was cleaning up the forge. It has a wooden deck around it. I mix chemicals and do messy things on the back corner. Last fall, I was mixing up a new batch of FC from crystalline FC and water, and used a large plastic pail. It got so hot it melted the pail, and the FC ran all over the boards. I washed them down with water for about an hour, and besides a little color, all looked fine.
I walked across that spot last Friday and noticed a little give in the boards. I pushed down harder with my foot, and two adjacent boards crumbled. I have to replace the deck boards covering about sixteen Sq.Ft. From what I can tell, the FC reacted with the treatment in the wood and left it as porous wood. The winter and spring rains did the rest.
 
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