# Does copper react with HCl when current is present?

Copper does not react with hydrochloric acid, according to many sources. However, I found an experiment posted in a video, which I will try to repeat, that shows a copper pipe dissolving into HCl and plating a nail when the copper pipe and the nail are connected to a 12-volt battery, becoming electrodes. No other chemicals, according to the video, are present. How does the electrical current cause the copper to react with the HCl when otherwise it would not?

• Electric current is stronger than anything in chemistry. It would make pretty much anything react with anything else. – Ivan Neretin May 27 '17 at 12:01
• – Loong Sep 24 '17 at 9:16

A reaction between copper metal and hydrochloric acid would go something like this: $$\ce{Cu + 2HCl -> CuCl2 + H2}$$ ...which we can write as: $$\ce{Cu + 2H+ -> Cu^2+ + H2}$$ If we break this up into half reactions, we get: $$\ce{Cu -> 2e- + Cu} ~~~E°=-0.34~V$$ $$\ce{2H+ + 2e- -> H2} ~~~E°=0.00 ~V$$ If we add the voltages together, we get the cell potential of the combined reaction is $-0.34+0.00=-0.34~V$. Since the cell potential is negative, the reaction is not spontaneous, so the reaction is not going to occur without any artificial interference ($\Delta G°=-nFE°_{cell}$).

However, if you connect a battery (galvanic cell) to this reaction, you can supply the necessary electrons for this reaction to occur (electrolytic cell). Since you are connecting a 12 V battery, there is more than enough voltage to cause this reaction to occur.

When I want to plate small parts with copper, I submerge lots of waste copper and the steel part into muriatic(HCl) acid. The oxides on both materials dissolves quickly and overnight there deposits a layer of copper on the steel suitable for forming a passivation layer. No electricity involved.