| Thanks for responding to my question, I have a few more if you'd be so kind as to answer them. First, the titanium anode didn't corrode at all, it was the steel cathode. But by being the cathode, wouldn't it have cathodic protection from corrosion? Also, we just studied electrochemistry in my chemistry class. From this knowledge, I am assuming that the positive calcium and magnesium ions in the water are being reduced by electrons supplied by the electric current, but what makes them electroplate on the steel structure and not the walls of the tub as well? And where do the carbonate ions come from? I didn't know that they were present in sea water. Each subject received the same voltage, but a different amount of current (6v:300mAmp, 400mAmp, 700mAmp), would the total kilowatt hours be the same for all of them? And why would the current make a difference?
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Answer 1:
First, the titanium anode didn't corrode at all, it was the steel cathode. But by being the cathode, wouldn't it have cathodic protection from corrosion? Remember that for cathodic protection to occur, technically you should have a more negative electrochemical potential for the anode than for the cathode. I don't have the numbers with me, but it probably is the case that for your system, the titanium has a higher potential than for the iron in the steel mesh.
Also, we just studied electrochemistry in my chemistry class. From this knowledge, I am assuming that the positive calcium and magnesium ions in the water are being reduced by electrons supplied by the electric current, but what makes them electroplate on the steel structure and not the walls of the tub as well? Recall that the electrochemical reactions in your system are taking place due to a difference of electric potential (that is, a voltage) between two electrodes. The difference in voltage is maximized on the electrode's surface, and hence, that's where you will be able to see the solids grow. If your system were a steel bucket full of sea water and the titanium anode were located in the middle, you could use the bucket itself as your cathode, and you would see the solids growing on it.
And where do the carbonate ions come from? I didn't know that they were present in sea water. The oxygen molecule is a very reactive chemical species. It reacts with a lot of molecules, such as hydrogen (forming dehydrogenate oxide, a.k.a. water), iron (forming iron oxide, a.k.a. rust) and carbon (forming carbon dioxide, a.k.a. CO2), among many others.CO2 in particular, is present in a small concentration in the atmosphere, and is the major contributor (but not the only one) to global warming. CO2 is mildly soluble in water (hence the fizz in your soda) and in sea water as well. When CO2 dissolves in water, it can interact and react with water in a number of ways, including ionization under an electrical load.
In case you want to learn more, in the March issue of the "Scientific American" magazine, there's an article on the acidification of the seas, which touches on the issue of carbon dioxide in the atmosphere and its reactions when dissolved in sea water.
Each subject received the same voltage, but a different amount of current (6v:300mAmp, 400mAmp, 700mAmp), would the total kilowatt hours be the same for all of them? And why would the current make a difference? The total amount of energy that you provide to the system is the product of the current times the potential. Hence if you change either of those two variables, you are changing the amount of energy supplied to the system. In your case, you kept the potential (i.e. the voltage) fixed, and varied the Amps (i.e. the current), hence in each case you supplied a different amount of energy, and therefore you can expect that you grew different amounts of solids for each run. That's why the current makes a difference. So does the voltage. Just to illustrate the point: Why are there AAA, AA and C size batteries, if all of them are 1.5 volts?
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