Electrochemical methods for on-site determinations of corrosion rates of rebars

A review on the available electrochemical methods is presented for the on-site determination of rebar corrosion rate. In real size structures the methods available at present may be classified in three groups: A) Confinement of the applied electrical signal, B) Measurement of the lateral spreading of the electrical signal and C) Minimization of this lateral spreading. From these three alternatives, the first one has been implemented in a device that is now currently used for on-site measurements. This device is based in a ''controlled'' guard ring. In real size structures, the normal values of corrosion rates recorded are of the same order of magnitude of those previously measured in laboratory experiments. The levels are classified in: negligeable, low, moderate and high. The gaps in the knowledge which still need to be investigated are also, commented: 1) unconfined measurements, 2) effect of counterelectrode size, 3) the true meaning of the corrosion rate measured, 4) constant B value, 5) current distribution around rebar perimeter 6) relation between mean corrosion rate and maximum pit depth and 7) identification of local corrosion. Finally, the role of embedded sensors on the monitoring of rebar corrosion risk, is mentioned.