SnailsAttack
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Metal displacement of aluminum by a copper salt
Simple question: how do copper salts displace aluminum metal? Like, if I soak aluminum scrap in copper acetate it starts bubbling and the solution
turns clear within 5 minutes. How is it penetrating the aluminum oxide passivation layer? Most other oxides seem highly resistant to metal
displacement reactions; notably those of titanium, iron, and manganese.
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Rainwater
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Simple answer
For stp conditions in aqueous solution, you want to review the reactivity series.
https://en.m.wikipedia.org/wiki/Reactivity_series
This layer is not perfect. If you were using anodized aluminum, it would be very resistant to this attack, taking much longer to react.
Al + 2H2O = H2 + Al(OH)2
As soon as the aluminum surface reacts with water, al ions are formed. This is a white powder that is not very soluble. Iron is very reactive to. Just
look for some rust. titanium is as well, the oxide layer formed is very resistant to attack.
In solution, you have aluminum, water, and copper salt.
Assuming your at room temp, and 1 atm of pressure, you can use the stp table linked above.
Al+ H+ OH- Cu+ SO4-
Let's ignore the water for simplicity, which leaves Al+ Cu+ SO4-
Because copper is lower down on the table, it will accept an electron from aluminum
Now you have Cu Al+ SO4-
You would be much better off reading this out of a textbook than from me. The reaction mechanisms are much more complex in reality. Research gibbs
free energy for a more accurate method of perdicting the products of a reaction.
"You can't do that" - challenge accepted
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SnailsAttack
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Quote: Originally posted by Rainwater  | Simple answer
For stp conditions in aqueous solution, you want to review the reactivity series.
https://en.m.wikipedia.org/wiki/Reactivity_series
This layer is not perfect. If you were using anodized aluminum, it would be very resistant to this attack, taking much longer to react.
Al + 2H2O = H2 + Al(OH)2
As soon as the aluminum surface reacts with water, al ions are formed. This is a white powder that is not very soluble. Iron is very reactive to. Just
look for some rust. titanium is as well, the oxide layer formed is very resistant to attack.
In solution, you have aluminum, water, and copper salt.
Assuming your at room temp, and 1 atm of pressure, you can use the stp table linked above.
Al+ H+ OH- Cu+ SO4-
Let's ignore the water for simplicity, which leaves Al+ Cu+ SO4-
Because copper is lower down on the table, it will accept an electron from aluminum
Now you have Cu Al+ SO4-
You would be much better off reading this out of a textbook than from me. The reaction mechanisms are much more complex in reality. Research gibbs
free energy for a more accurate method of perdicting the products of a reaction. |
Oh, I'm familiar with the MRS I just wasn't sure how the copper acetate was getting past the oxide layer (or otherwise if it was reacting with the
aluminum oxide itself).
So you're saying it's because it can get through the thinner gaps in the layer?
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reactofurnace
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| Quote: Originally posted by Rainwater | Simple answer
For stp conditions in aqueous solution, you want to review the reactivity series.
https://en.m.wikipedia.org/wiki/Reactivity_series
This layer is not perfect. If you were using anodized aluminum, it would be very resistant to this attack, taking much longer to react.
Al + 2H2O = H2 + Al(OH)2
As soon as the aluminum surface reacts with water, al ions are formed. This is a white powder that is not very soluble. Iron is very reactive to. Just
look for some rust. titanium is as well, the oxide layer formed is very resistant to attack.
In solution, you have aluminum, water, and copper salt.
Assuming your at room temp, and 1 atm of pressure, you can use the stp table linked above.
Al+ H+ OH- Cu+ SO4-
Let's ignore the water for simplicity, which leaves Al+ Cu+ SO4-
Because copper is lower down on the table, it will accept an electron from aluminum
Now you have Cu Al+ SO4-
You would be much better off reading this out of a textbook than from me. The reaction mechanisms are much more complex in reality. Research gibbs
free energy for a more accurate method of perdicting the products of a reaction. |
Well said
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Rainwater
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Yes/no basicly.
The reaction of vinager on aluminum metal is faster than on aluminum oxide.
Both reactions create the same water soluble salt.
"You can't do that" - challenge accepted
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Fulmen
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The oxide layer is always slightly porous and single ions are pretty small. The rest is, as the french say, c’est la vie.
We're not banging rocks together here. We know how to put a man back together.
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