I am doing electrolysis of water to collect the hydrogen and I'm running into a problem: on the positive side I'm using graphite from a pencil (I cannot use any other material because it corrodes too fast) and on the negative side I was using copper. Copper was working really fine, the water was clear and no problem. But I don't have copper with a big surface area so I decided using aluminum (from coca cans) and my solution started to get dirty because of the aluminum and the aluminum is slowly disappearing.

Why? Any other eletrode that I used for the negative pole was not corroded (only on the positive pole everything corrodes). Why is aluminum making my water dirty? Do you think if I use iron this problem will not happen?

  • $\begingroup$ Aluminum is pretty active. Once the passivation layer is breached, it would react with water quite readily. $\endgroup$ Oct 23, 2016 at 15:58
  • $\begingroup$ Please don’t use shorthands like $-$ or $+$ for negative and positive poles/cathode and anode, respectively. It took me quite a while to understand that this question is actually valid. Also, please don’t resort to colloquialisms such as cause and try not to forget any apostrophes. Thanks. $\endgroup$
    – Jan
    Oct 23, 2016 at 20:47
  • $\begingroup$ You'll probably need to add more information in order to get any useful answers. What, if anything, did you add to your water? What potential are you using? Could you take a picture of the aluminum cathode and the water after a test where you've observed the aluminum to dissolve? $\endgroup$
    – hBy2Py
    Jan 2, 2017 at 16:13

1 Answer 1


If you are using salt to make the solution more conductive the process will cause the creation of Sodium Hydroxide, which will react with aluminium.


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