Introduction to electrochemical series and metal corrosion.
A potential difference Between an anode and a cathode can be measured by a voltage measurement device, but as the absolute potential of an anode or cathode cannot be measured directly - all potential measurements are made against a standard electrode. The default electrode potential is defined as zero and the measured potential difference can be considered absolute.
Standard hydrogen electrode
- The half-cell in which the hydrogen reaction occurs is called Standard Hydrogen Electrode - She
Standard electrode potential
- The potential difference measurement between a metal M and the standard hydrogen electrode - She
The electrochemical series (electro-motor series) is a list of metals arranged in order of its standard potentials for hydrogen electrode:
|
Element
|
Electrodes potential
(volts) |
|---|---|
| Lithium | -3,04 |
| Rubidium | -2,92 |
| Potassium | -2,92 |
| Calcium | -2,87 |
| Barium | -2,80 |
| Sodium | -2,71 |
| Magnesium | -2,37 |
| Beryllium | -1,85 |
| Aluminum | -1,67 |
| Manganese | -1,19 |
| Zinc | -0,76 |
| Chrome | -0,74 |
| Tungsten | -0,58 |
| Ferro | -0,44 |
| Cadmium | -0,40 |
| Cobalt | -0,28 |
| Nickel | -0,24 |
| Lata | -0,14 |
| To drive | -0,13 |
| Hydrogen | +0,00 |
| Antimony | +0,10 |
| Copper | +0,34 |
| Iodine | +0,54 |
| Talk | +0,80 |
| Mercury | +0,85 |
| Bromo | +1,07 |
| Platinum | +1,20 |
| Chlorine | +1,36 |
| Gold | +1,50 |
| Fluorine | +2,87 |
Observation! - Superior metals in the electrochemical series shift lower metals in the series - which means that by connecting two metals with different potentials, the metal with the smallest potential corrói.
Corrosion Problem When connecting copper and iron/steel
A very common connection in piping systems are copper and iron/steel. With this connection the iron/steel corrói often faster than iron/steel alone.
Source: https://www.engineeringtoolbox.com/electrode-potential-d_482.html
