The aim of this work is to study the protection of steel reinforcement against corrosion by pretreatment in phosphate (Na3PO4) solution. The work has been carried out using electrochemical techniques, i.e. corrosion potential Ecorr, polarisation resistance RP and electrochemical impedance spectroscopy (EIS) measurements. The results have been validated by a gravimetric method. It has been stressed that RP measurements, determined by DC techniques, include the charge transfer resistance Rt plus the resistance associated with the redox process Rox, both determined by EIS. Also the results have demonstrated that the treatment of the rebar by immersion in the Na3PO4 (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which is able to resist longer the action of chlorides to initiate corrosion. However, the resistance of the passive layer against chloride depends on the duration of the treatment by immersion of the rebar within the phosphate solution.The aim of this work is to study the protection of steel reinforcement against corrosion by pretreatment in phosphate (Na3PO4) solution. The work has been carried out using electrochemical techniques, i.e. corrosion potential Ecorr, polarisation resistance RP and electrochemical impedance spectroscopy (EIS) measurements. The results have been validated by a gravimetric method. It has been stressed that RP measurements, determined by DC techniques, include the charge transfer resistance Rt plus the resistance associated with the redox process Rox, both determined by EIS. Also the results have demonstrated that the treatment of the rebar by immersion in the Na3PO4 (0·5M) solution favours the formation of a passive layer on the steel rebar surface, which is able to resist longer the action of chlorides to initiate corrosion. However, the resistance of the passive layer against chloride depends on the duration of the treatment by immersion of the rebar within the phosphate solution.