Electrolytic corrosion of metals
Drinking water, natural gas and domestic wastewater flow through metal structures and are stored in underground tanks, all of which are subject to corrosion.
Any facility with metal components is subject to this phenomenon, which occurs when materials, such as iron and carbon steel, come into contact with an electrolyte, such as soil.
Corrosion is not a phenomenon that can be completely eradicated, but specific measures can be taken as early as the design and construction stage to significantly reduce its effects and ensure the proper functioning, durability and safety of the systems.
Passive and active cathodic protection
The most effective solution in this field is cathodic protection, an electrolytic corrosion prevention technique that is applied to metal components that are in contact with electrically conductive environments.
Essentially, this involves running a direct current between an electrode – the anode – and the surface of the component to be protected – the cathode. The current lowers the electric potential of the metal surface such that it significantly slows down corrosion.
Depending on the technology used, it is possible to implement passive cathodic protection with coatings and inhibitors, or active cathodic protection using sacrificial anodes or impressed current to counteract faults and gaps in the coating caused during installation or by deterioration.
After they are commissioned, these systems must be monitored to assess their effectiveness and to carry out any maintenance, if required. To this end, cathodic protection measuring points are identified on the distribution, transport and storage networks during the design stage. By acquiring the tube-to-ground potentials of the pipeline to be protected, manual checks can be scheduled on the measuring points. These can be replaced or supplemented by the installation of electronic devices capable of continuously acquiring the potentials and sending them to a data collection centre that automatically analyses the parameters and, where required, fulfils the network remote control obligations by means of alarm signals that allow the anomaly to be identified and quickly resolved.
Cathodic protection applied to metal pipes
Regulatory and operational aspects
The quality of the cathodic protection service is determined differently depending on the country or according to internal company specifications.
However, any underground metal structure must comply with international standards that require the use of the electric potential between the metal structure and the ground as a criterion for defining its protection, i.e. the engineering acceptability of the corrosion rate.
As a result, cathodic protection is implemented in almost all underground structures, especially those in which potentially dangerous or expensive fluids, such as oil and natural gas, are piped.
According to current international regulations, the measurement methods are identified according to the acquisition technique: EON in the case of measurements for switched-on systems, used to generally assess the electrical parameters of the cathodic protection, EOFF in the case of the technique for switched-off systems, which can also be obtained with the new, latest-generation acquisition units featuring an integrated cyclic switch in combination with electrodes with anodes that simulate the electro-chemical characteristics and behaviour of the bare pipe.
In Italy, the sector is regulated by APCE, the Association for Protection from Electrolytic Corrosion recognised by ARERA, the independent administrative authority that regulates energy, grids and the environment, as the competent technical body for the definition of guidelines in the field of cathodic protection for metal pipelines used for distribution, transport and flow lines connecting natural gas storage plants. The quality of service is assessed using the KT algorithm, which assigns a score to each electrical system: annual compliance is only achieved if it is greater than or equal to 60 points out of a maximum of 100.
Pietro Fiorentini’s experience in cathodic protection
The Company started developing and creating cathodic protection monitoring systems in 2016 with the acquisition of the Tecnosystem Group, a renowned Italian company in data acquisition services for the sector. Pietro Fiorentini’s product portfolio therefore expanded to easily installable field acquisition units that automatically record and send the main electrical parameters to data collection centres without any kind of manual control.
In 2019, the Company provided new cathodic protection monitoring software to its French customer GRTgaz: Service2Business. The platform fulfils all the characteristics of remote monitoring while also improving the centre and service procedures offered. Since 2020, S2B has also been available to customers in the Italian market and is able to interface with NEXT and Drone Kompact, Pietro Fiorentini’s devices for the monitoring and remote control of cathodic protection systems.
During the same year, Pietro Fiorentini built a cathodic protection test field at its factory in Rosate (Milan), certified in accordance with UNI EN ISO 15257. The facility meets the training needs of internal and external staff and is used to develop applications and new products. It is also made available to polytechnics, universities and research institutions that request to use it in order to carry out tests, studies and measurements of various kinds.
In order to provide its customers with continuous regulatory updates, Pietro Fiorentini attends both the national UNI and international EN and ISO technical working tables and the APCE’s Technical and Training Committees. In order to comply with the latest specifications and the new technical standards within the sector, the Company is now working to develop latest-generation dataloggers for remote monitoring with communication modules that can support the new 4G/LTE technology and an on-board cyclic switch for EOFF measurements.