What Does Negative Charge Mean?
A negative charge is an electrical property of a particle at the subatomic scale. An object is negatively charged if it has an excess of electrons, and is uncharged or positively charged otherwise. Such electrochemical activity plays a vital role in corrosion and its prevention.
Corrosionpedia Explains Negative Charge
Corrosion can be prevented by endowing the metal to be protected with a negative charge. The maintenance of a continual negative electrical charge over the surface of a metal is known as cathodic protection. The principle of cathodic protection involves connecting an external anode to the metal to be protected and the passing of an electrical DC current so that all areas of the metal surface become cathodic and therefore do not corrode.
If, for example, electrons are passed into the metal and reach the metal/electrolyte interface (a cathodic current) the anodic reaction will be stifled while the cathodic reaction rate heightens. The process is known as cathodic protection and can only be applied if there is a suitable conducting medium such as soil or water through which a current can flow to the metal to be protected.
The main advantage of cathodic protection over other forms of anticorrosion treatment is that it is applied simply by maintaining a DC circuit and its effectiveness may be monitored constantly. Generally, cathodic protection is applied to a coated structure to provide corrosion control to areas where the coating may corrode or undergo damage. It may also be added to existing structures to prolong their life.
Structures that are typically protected by cathodic protection include:
- Ships’ hulls
- Storage tanks
- Jetties and harbor structures
- Steel sheets, tubular and foundation pilings
- Offshore platforms, floating and subsea structures