State of the art on the calculation of anodic resistance for cathodic protection of steel in concrete

¹ Résilience & Maintenance du Béton, 69250 Fleurieu sur Saône, France
² SECCO Corrosion Consulting, 78140 Vélizy-Villacoublay, France

Abstract

For the design of cathodic protection (Impressed Current Cathodic Protection (ICCP) or Sacrificial Anode Cathodic Protection (SACP)) of steel in concrete using drilled-in discrete anodes, the rectifier output voltage and current are selected (for ICCP) based on a multi-criteria analysis (steel surface, concrete performances, results of material and corrosion diagnostics, oxygen availability, exposure to pollutants, expected service life, etc.). However, the rules for calculating anodic resistance (which makes a major contribution to overall circuit resistance) are not universally accepted in the profession, since the calculation rules used for cathodic protection of buried or immersed metal structures, which could be used by analogy, assume that the electrolyte is infinite, which cannot be the case in concrete. As a result, some designers are now skipping this fundamental step. Cumulative polarization measurements over the commissioning period have been carried out for several years on different projects, with different anode systems, and the results demonstrate consistency in the shape of the curves obtained and confirm the difficulty of assessing the contribution of the various parameters to be considered to enable the drafting of a robust and realistic limit state design hypothesis note. The final section concludes with the value of pilot testing in securing the design hypothesis.