Monitoring of steel corrosion in concrete in the presence of IFKhAN-78 corrosion inhibitor by electrochemical methods. Potentiometry and polarization measurements

A number of inhibitory compositions of various nature, including migrating inhibitors (MCI), have been proposed to protect concrete steel reinforcement from corrosion.In this work, we investigated the effect of the migrating corrosion inhibitor IFKhAN-78, which differs from more common IFKhAN-80 inhibitor in the ratio of its components.We studied the laboratory concrete samples prepared from a mixture of cement, sand and water (mass fractions 1:2:0.4) and reinforcing steel St3 A500.The experiments were carried out in 3% NaCl base solution.During the 6-month corrosion tests, the behavior of concrete samples without additives in the base solution and with an addition of 3% IFKhAN-78 to the solution, as well as samples with an addition of 3% IFKhAN-78 to the concrete mass (relative to cement) with tempering water, was compared.Regular monitoring of the samples corrosion state during exposure in solution by the value of the open circuit potential and by the corrosion current measured by Tafel curves slopes showed that the concrete samples without additives, as a rule, maintained a passive state until the very end.The samples with the inhibitor added to the concrete mass remained passive only for the first month after immersion in the base solution.Then their corrosion resistance deteriorated.At the same time, additional periodic impregnation of the surface with the inhibitor ensured a reduction in the rate of corrosion of steel for a certain period (up to 50 days).It is assumed that the increased concentration of surfactants in the studied inhibitor contributes to its leaching from the pores of concrete and the counter diffusion of chloride ions from the solution into the metal, causing an acceleration of its corrosion.Thus, the IFKhAN-78 migrating inhibitor cannot be recommended for mixing into a cement mass when preparing concrete, since if the sample is under a layer of chloride-containing solution for a long time after a short period of passivity of the reinforcement, its corrosion rate can increase significantly.