[Byrne]

Having some trouble understanding how impressed current works in cathodic protection.  

Say we wanted to protect an iron object.

What the impressed current entails is basically the negative terminal of a battery being connected to the iron object and the positive terminal to, let's say, an inert carbon electrode.  This is what I have in my notes:

In a battery, electrons flow from the negative terminal to the positive terminal.  So if the negative terminal of a bettery is connected to the iron object and the positive terminal connected to the inert carbon electronde, an electric current is forced to flow through an electrolyte such as ground water, from the carbon electrode... But I thought electrons flow from negative terminal to positive terminal... is the carbon electrode not attached to the negative terminal?  Why is it that my note would say the electric current is flowing from the carbon electrode?  How is it that if the iron is attached to the negative electrode, that it becomes the cathode?  Do electrons not flow from the negative terminal of a battery?

I'm confused.

[mike]

Electrons actually flow from negative to positive.

Conventional current flows from positive to negative.

[Byrne]

Electrons actually flow from negative to positive.

Conventional current flows from positive to negative.

Isn't that what I said in my question, though?  Electrons are flowing from the negative terminal to the positive terminal.  The iron is connected to the negative terminal.  How does this make it the cathode?

[mike]

Sign convention swaps between a galvanic cell and an electrolytic cell.

In Galvanic cell (ie battery) the anode is negative while the cathode is postive.

In Electrolytic cell the anode is positive while the cathode is negative.

[Byrne]

Sign convention swaps between a galvanic cell and an electrolytic cell.

In Galvanic cell (ie battery) the anode is negative while the cathode is postive.

In Electrolytic cell the anode is positive while the cathode is negative.

Ahhh...

That's right.  Thanks a lot.