Una breve conversazione sulla protezione catodica
Cathodic Protection: is there still margin for improvements?
Everyone has his own certainties, among those of a good engineer there is the one that states that whatever metal he will use in his project, it will probably suffer from corrosion issues.
A wide range of processes, materials and technologies are available today, aimed at preventing and controlling the onset of corrosion. Among them: the development of new high performance/corrosion resistant metallic alloys, the use of corrosion inhibitors, the application of protective coating (metallic, plastic, bituminous or ceramic) or the application of a cathodic protection system. Quite often, two or more of these techniques are applied at the same time, aimed at increasing the safety margin. As an example, while present day coatings are quite efficient, the coupling with a cathodic protection system guarantees the prevention of localized corrosion attack occurring at the coating defects. Where the environmental conditions are extremely demanding, such as for subsea well heads, structures are maintained against corrosion by a combination of cathodic protection, coatings and corrosion resistant materials.
Corrosion prevention by cathodic protection (CP) requires that metals are exposed to conductive environments and is based on the circulation of a continuous current between an electrode (anode) and the structure to be protected (cathode). For Impressed Current systems (ICCP) an external DC feeder supplies current to the electric circuit transforming the metallic structure – that naturally would be a corroding anode – into a cathode, and consequently shifting the occurrence of anodic reactions on an external, extremely durable, anode. Because of its efficiency, especially when joined with other corrosion prevention strategies, cathodic protection has deeply permeated several industrial markets including pipelines, refineries, above and underground storage tanks, water, wastewater, concrete, infrastructure, offshore and marine.
Although rather simple in theory, the setting of an efficient and durable cathodic protection system is extremely complex, due to the countless variables that must be considered: anode types, geometry and placement, temperature, stagnancy of flow conditions, protection potential, current distribution, eventual electric interferences, monitoring techniques etc.
While, over the years, the factors driving the design of cathodic protection setting and monitoring equipment have not changed much, our understanding of the process of cathodic protection has evolved, allowing us to continuously improve the protection performances. Deep sea water structures are probably among the most complex systems requiring protection because of the harsh environmental conditions and their remoteness; however due to the requested high standard, leaving little room for error, extremely sophisticated models and remote monitoring systems are being deployed to guarantee a reliable corrosion protection. Conversely, if the “highest quality” cathodic protection data exists for deep water applications, it appears there is a gap in the knowledge of shallow water systems: while they are all functional and serve the purpose, the designs used are ultra-conservative, thus losing the opportunity of saving a relevant amount of money.
All the above is related to the engineering aspects of a cathodic protection system; as Chemical Newtech, we have been producing ICCP anodes for ten years: we focus on the development and the production of activated titanium anodes, also known as Mixed Metal Oxides electrodes (MMO). Since the end of the seventies, when graphite anodes started to be replaced by MMO electrodes, the latter still represent the state of the art in terms of ICCP anodes.
Activated titanium electrodes offer high chemical stability, long life, low consumption rate, excellent conductivity and design flexibility. Although probably less crucial then the full engineering of a cathodic protection system, the production of MMO anodes still has room for innovation and optimization.
Chemical Newtech is highly committed in the development of efficient, durable and reliable MMO anodes, aided in its research and development activities by electrochemistry researchers from the University of Milan, with whom we have established a working relationship over the last few years.