Aluminum versus Mercury 1

[yokefellow]

Is the presence of oxygen required for mercury to dissolve aluminum?

 

[Rich2001]

Two differing processes with the mixture of aluminum and mercury.

The first process - oxygen is required This is a common classroom demonstration and the explanation is always that one is seeing oxidation of the aluminum facilitated by mercury's disruption of its oxide layer.

The second process - oxygen is not required
Liquid Metal Embrittlement. Hg wets the the grain boundaries, causing the grains to unzip.

Earlier this year in Moomba at a Natural gas processing facility a fire and explosion occurred due this phenomenon.

http://www.ferret.com.au/articles/97/0c01e497.asp

When Hg from entrained in the natural gas found it was into an aluminum coldbox (heat exchanger) causing a catastrophic event to occur.

Other LME pairs
Base Metal - Liquid Metal Environment

Aluminum - Gallium
Aluminum - Mercury
Brass - Mercury
C-276 (Hastalloy) - Silver Solders
Copper - Mercury
Copper Beryllium - Mercury
Cupronickel - Lead
8-9% Cr Martensitic Steel - Lithium
Steel - Lithium
Steel - Tin
ASTM A723 Steel - Indium
ASTM A723 Steel - Gallium
Austentic Stainless Steel - Zinc

 

[Flesh]

yokefellow, I am curious:
What experiment/application is to be done with these two metals "outside" of the classroom?

 

[yokefellow]

I'm in search for a fairly strong material that can dissolve quickly. It’s a holding pin that needs to dissolve within a certain time frame. The proposed environment is about 10k subsurface.

 

[SMF1964]

For liquid metal embrittlement, the crack growth rate is fairly substantial - I suggest looking through the ASM metals handbook on Failure Analysis & Prevention. There is a section on liquid metal embrittlement, of aluminum/mercury in particular. But as Rich2001 indicates, you are not dealing with dissolution but with intergranular crack propagation.