Cathodic protection is an electrochemical technique used to safeguard metal structures from corrosion. It works by turning the entire surface of the metal to be protected into the cathode of an electrochemical cell, thus preventing the loss of electrons that causes rust.
It is applied to structures immersed in conductive environments (electrolytes) such as soils or water, but it is not effective for structures exposed only to the atmosphere.
There are two ways to apply this protection:
- Galvanic (or “sacrificial”) anodes: The metal to be protected (e.g. steel) is connected to a more “active” or less noble metal, such as zinc, magnesium or aluminium. This second metal oxidizes (“sacrifices”) in place of the main structure.
- Impressed current: An external direct current power supply is used. This pushes electrons toward the metal structure, keeping it in a state of electrochemical safety without necessarily consuming metal anodes
ESA – LIST OF BENEFITS & SERVICES
- Design support for the cathodic protection of new or existing metal structures, underground or submerged.
- Construction of cathodic protection systems from scratch.
- Adaptation and restoration of existing cathodic protection systems.
- Surveys of the electrical status of underground structures and external electrical interference.
- Measurement campaigns for the remediation of underground or submerged structures.
- Surveys for the identification of the corrosion risk index.
- Management and controls in accordance with the directives of the AEEG Authority (ARG – gas resolutions)
- Site surveies (onshore)
- Soil resistivity measurements
- Insulation tests
- ON – OFF Potential Measurement Methods
- Close Interval Potential Survey (CIPS)
- Insulation leak location measures on underground metal pipes:
- Transverse Gradient Method (DCGT)
- Longitudinal gradient method (DCGL)
- Electromagnetic attenuation method
- Pearson Method (AC)On/Off readings
- Stray current analisys
SPECIALIST ACTIVITIES
Cathodically protected structures can often be subject to external electrical interference due to the presence of extraneous sources, such as industrial plants, direct current communication systems, traction systems and cathodic protection systems belonging to third parties. ESA, with the help of specific instrumentation and thanks to its consolidated experience in the sector, is able to monitor and manage the various problems that may arise, identifying the specific areas with anodic potential, in order to restore a correct electrical state of protection.
PLANT MANAGEMENT & MAINTENANCE
Proper management of underground structures is now a regulatory obligation and is based on an accurate analysis of the resistivity of the subsoil, on the control of the good electrical insulation of the network and on the constant monitoring of the operating parameters of the systems. The management and maintenance services offered by ESA meet the needs of the customer, respecting its operational organization, always guaranteeing the required quality standards, efficiency, cost reduction, the elimination of paper supports and, above all, the elimination of risks. The monitoring system, thanks to the use of appropriate technologies, allows an efficient and reliable connection between the activities in the field and the decisions of the control centers, so as to provide not only the alignment of data, but also information on the activity of the operators, internal and/or external.
ELECTRICAL STATUS SURVEY
ESA uses methods that, through instantaneous and/or recorded measurements, allow the monitoring of the electrical state of a network, or part of it, such as to identify electrical interference (stray currents), the electrical characteristics of the subsoil and the state of deterioration of the protective coating. The analysis of these parameters made it possible to determine the anodic and cathodic areas and, therefore, to design an effective cathodic protection system and/or modify the existing one by adapting it to changes in the electric field which by its nature is variable over time.
COMMON PROBLEMS
One of the most serious and frequent problems in the management of underground networks is third-party excavations that can change the electrical state of a structure. Often the safety devices intervene by interrupting the power supply to the control unit, leaving the pipes out of protection. For this reason, the systems and measuring points must be subjected to simple but continuous checks in order to monitor changes in the electrical status. Field checks are essential and must be constant and able to guarantee a long life of the structure and, therefore, investments.