Protection of reinforcement steel corrosion by phenyl phosphonic acid pre-treatment PART I: Tests in solutions simulating the electrolyte in the pores of fresh concrete

The carbon steel electrodes were first treated by immersion in 0.1 M phenyl phosphonic acid (C6H5P(O)(OH)2, PPA) solution during 24 or 72 h, then they were transferred into the corrosion test solution representing interstice pore electrolyte polluted by seawater: (sat. Ca(OH)2 + 0.5 M NaCl) to evaluate the protective effectiveness of the pre-treatment. The investigation was performed essentially by polarisation curves and electrochemical impedance measurements with rotating disc electrode. Very high protective effect was observed with steel pre-treated during 72 h with stationary electrode. From polarisation and electrochemical impedance spectroscopy experiments, the protective efficiency was found to be in the 90-99% range for 72 h pre-treatment. This protective property remains effective even one month immersion. EDS analysis showed the presence of the phosphorus on the steel surface, probably due to the presence of iron-PPA complex.