Introduction to electro chemical series and corrosion of metals
The potential difference between an anode and a cathode can be measured by a voltage measuring device. The absolute potential of an anode and a cathode cannot be measured directly, but by defining a standard electrode all other potential measurements can be made against this standard electrode. If the standard electrode potential is set to zero the potential difference measured can be considered as an absolute potential.
Standard Hydrogen Electrode
- The half-cell in which the hydrogen reaction takes place is called the Standard Hydrogen Electrode - SHE
Standard Electrode Potential
- The potential difference measured between metal M and the Standard Hydrogen Electrode - SHE
The electro-chemical series (electro-motive series) is a list of metals arranged in order of their standard potentials to the hydrogen electrode:
|Element||Electrode Potential |
IMPORTANT! Metals higher in the electrochemical series displaces metals lower in the series, which means that when connecting two metals the metal with the lowest potential corrodes.
Corrosion Problems Connecting Copper and Iron/Steel
A very common connection in piping systems is copper and iron/steel. In a connection like this the iron/steel corrodes many times faster than the iron/steel alone.