This paper gives an overview of long term performance up to 30 years in the field of cathodic protection of steel reinforcement in concrete in The Netherlands, focusing on impressed current systems based on activated titanium anodes. Case studies are presented including applications to large numbers of precast elements corroding due to mixed-in chloride with drilled in titanium anodes, parking garages with titanium strips in cementitious overlays and industrial floors with titanium mesh in overlay. Based on observed failures and replacements, analysis of working life of various types of systems and components and end-of-life considerations are given. CP has become a fully accepted method of securing safety and serviceability of buildings and infrastructure that are prone to corrosion. Observations show that with activated titanium based systems, very long service lives can be obtained. The activated titanium itself keeps working well beyond the observed period of 30 years. Some other components have relatively higher failure rates. The repairs that were required in the cases discussed are dominated by failing anode-copper connections and to a minor extent power sources and potential sensors.

This paper will report on long term behaviour of potential sensors used in cathodic protection of steel reinforcement in concrete. Cathodic protection (CP) systems, both impressed current CP (ICCP) and galvanic CP (GCP), need regular testing to establish the quality of protection. In addition, ICCP may require adjustment of output voltage or current. Various types of potential sensors have been used in relatively large numbers, comprised of true reference electrodes (RE) based on silver/silver chloride or Mn/MnO2 and decay probes (DP) based on a.o. activated titanium. Failures may occur due to loss of contact, drying out or cable defects. Test methods for potential sensors are discussed. Monitoring of about one hundred CP systems with several thousands of potential sensors over more than ten years allows to analyse their performance and failures. It appears that limited numbers of potential sensors fail over time, but in some cases an insufficient number of working potential sensors are left to properly monitor a CP system or zone. It is recommended to install more potential sensors than strictly needed in order to allow for failures and to maintain testability and save the high cost of installing new potential sensors later.