Caution: Problems to be Avoided

The presence of excessive negative elements accelerates corrosion of aluminum and lead structures because of the alkalinity of the environment brought about by the cathode. The alkaline conditions are also harmful to the coating systems and can cause loosening of the bonding of the coating. Hydrogen development at the cathode surface of the high strength steels can cause it to brittle and loose its strength. This can cause tremendous disaster on high strength steels.

Spark hazards caused by electric currents in hazardous areas must also be taken into serious consideration. Sacrificial anodes are self regulating and do not create conflict with the structure, but they must be periodically inspected to ensure supply of continued protection. This is where the important role of close interval surveys comes in.

Close interval surveys done at the cathodic periodic systems are very important to ensure that hazards are avoided in the protected structure. The presence of copper sulfate means corrosion in the structure and they are detected by the use of RTU Remote in the terminal unit.

A “stray current corrosion” phenomenon can happen when corrosion is increased on the auxiliary structure where the electric current is discharge to the electrolyte. An example is when a ship is anchored near a protected yacht, or a metal coated pipeline crossing another pipeline which is cathodic protected.

Important factors for the proper design of cathodic

Close interval surveys are done on immersed metallic structure like pipelines to determine the cathodic protection services required. This is done by measuring electrolyte dc on the metal surface. Close interval surveys are done on test station, test facilities and permanent half cells and data can be regularly viewed or collected.

Initial considerations for cathodic protection design are the modifications needed to the structure in order to incorporate the system and they are best made at the blueprint stages of the structure. For immersed structures, it is wise to visit the proposed site in order to obtain more information on the source of power supply, the presence of dc current and other interaction.

Close interval surveys are usually done before the design. The survey is done with a study to justify the financial viability of the proposed cathodic protection system while physical and chemical data are collected. However if the structure is already standing or existing, survey is done by measuring structure to soil elements to give important information to identify anodic and cathodic areas.

Important factors for the proper design of cathodic protection systems are;

· Calculation of current demand

· Anodes resistance to earth ground

· Location and quantity of the anode systems

· Power supply source

· Test stations and monitoring facilities

For onshore structures and pipelines, negotiation with the government, landowners and other interested third parties for groundbeds, cable routes, current supplies and transformer-rectifier locations is very important during the initial stages of the cathodic protection design systems.