Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: November 25, 2016

What Does Anode Mean?

An anode is a highly polarized electrode where electric current travels into an electrical device. Typically, the current's direction is always opposite to the flow of electrons.

To illustrate, electrons travel from the positive charge, or anode, into an electrical circuit. A mnemonic that is widely used to define an anode is ACID, which stands for "anode: current into device."


Corrosionpedia Explains Anode

A common misconception about the polarity of an anode is that it always carries a positive charge. This is due to the fact that anions, or negatively charged particles, move into the positively charged electrodes. The truth is that the polarity of an anode depends on the type of device or its mode of operation. In most cases, an anode has a positive charge in any device which takes in power, and carries negative charge when it is used in a device that gives off power.

The following are examples of anodes:

  • In a galvanic cell or discharging battery, the anode corresponds to the negative terminal since it is where the current travels into the battery.
  • In an electrolytic cell or recharging battery, the anode is positive since it is receiving current from other sources.
  • In cathode ray tubes, the anode is positive since it is where electrons travel out of the tube, whereas positive current enters.

There are several types of anodes:

  • Galvanic cell anode – This type of anode is a negatively charged electrode where electrons travel out through the circuit's outer portion.
  • Electrolytic anode – In the field of electrochemistry, the anode is the site of oxidation and contains the positive charge in contact with the electrolytic cell.
  • Diode anode – In semiconductor diodes, the P-doped portion corresponds to the anode and brings holes into the joint area. The holes where the anode supplies connect with electrons from the N-doped area, leading to a depleted region.
  • Vacuum tube – In vacuum devices like a cathode ray tubes, the anode is always positively charged and it gathers the electrons released by cathode via electric attraction.

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