What Does Driving Potential Mean?
Driving potential refers to a voltage difference between the anode and the steel structure. Driving potential across the corrosion cell circuits causes corrosion of the metallic structure. When there is no driving potential across the corrosion cell circuits, then no corroding current can flow (i.e., no corrosion occurs). Cathodic corrosion can be managed by controlling the driving potential of a corrosion cell.
Corrosionpedia Explains Driving Potential
Driving potential is the difference in potential between the anode and the cathode (steel structure).
The output current of the anodic material depends on the driving potential and the resistance between the anode and the structure to be protected (cathode). The output of the anode is determined by Ohms Law:
I = V / R
I = Anode output
V = Driving potential of the circuit
R = Resistance of the anode to the electrolyte
From Ohms Law, it is obvious that the magnitude of the corrosion cell current is linearly proportional to the driving potential between the anodic and cathodic areas and is inversely proportional to the resistance of the total path along which it flows. The total path resistance consists of:
- anode / electrolyte interface
- electrolyte itself
- electrolyte / cathode interface
- longitudinal resistance of the metallic paths traversed
In a galvanic anode system, the driving potential between the anode and cathode is quite low. The small potential difference, or driving potential, results in very limited current outputs in high-resistivity electrolytes (e.g., soil). It financially limits using galvanic systems on large or poorly-coated structures.
High potential anodes are an alternative to protect most buried metallic structures in soil. This will produce a higher driving potential than conventional sacrificial anodes and is suitable for buried structures in high-resistivity soil.