ELECTROCHEMICAL METHODS FOR THE MONITORING PROTECTION OF STEEL IN CONCRETE AND HOW 100 YEARS OF CATHODIC PROTECTION EXPERIENCE CAN BE UTILISED FOR THE PROLONGED LIFETIME AND SAFETY

摘要

Since more than 100 years Cathodic Protection has been used for the protection of metals in electrolytes and the last 50 years the technique, available products and understanding has been further developed. The last 10 years we have added the electronics and computer developments and reached a very user friendly and standardised level. Very few systems and products have this history and track records, and for steel in concrete we have approx. 30 years of international experience, but still the use of this technology is not considered normal, anyway not in Europe, and the requirements for testing, research projects and experts are common. The non-destructive testing (NDT) methods are often discussed and continuously a lot of money is invested searching for the ultimate technique and system that can find everything with high reliability. Parallel with Cathodic Protection the potential measurement techniques, products and system have been developed. The last 10 years systems for potential & resistance mapping (EPRM) of the reinforcing steel in concrete has been used more and more for monitoring and planning. This can be performed by means of a mobile data logger and electrodes for scanning of the concrete surface or by means of casted-in electrodes to enable the continuous monitoring of the structure. This technique could be used in a more wide extent for the repair pre-investigation and planning but require practical training and experiences by the users. However the interest and cost benefit by using this method is mostly related to the use or intended use of Cathodic Protection which is very strange. The paper explain how those techniques can be used with references to large projects. The most interesting systems and products today, the advantages and limitations. The ease of use of several of the products, anyone can design and plan the systems as well as installing. System monitoring do not need to be complicated, for the structure surfaces above the splash zone the potential must be changed very little to a more negative value, and in the water the ordinary Cathodic Protection criteria for steel is valid. The anodes can be used as reference electrodes using a simple interrupting rectifier for the continuous automatic control of the current output for smaller systems. Further standardisation and testing methods is requested by the users for products and systems. This is fairly simple by using the methods already established for similar ordinary types of products and systems used for concrete repair as by CEN standards.