Investigation On The Diffusion Behavior And Corrosion Resistance Of Corrosion Inhibitors In Concrete

Corrosion inhibitor is an important measure to protect steel from corrosion in concrete.At present, for the assessment of rebar corrosion and corrosion inhibitor, more attention ispaid on the engineering application. Traditional electrochemical methods are mostlyconfined to the overall electrochemical process of steel, and rarely the uneven corrosion.This thesis studied the initiation and evolution of local corrosion of rebar underconcrete by5×20array wire beam electrode（WBE） in space and time. By the help ofdiffusionelectrolytic cell,3%NaCl solution permeated into the concrete sample in a certaindirection, to speed up the corrosion of WBE in dry and wet cycles. Each electrode of WBEwas weakly polarized to a constant value, and simulated the evolution of corrosion areaalong with Cl-penetration and dissolved oxygen diffusion by the anodic current distributionof WBE. Adding corrosion inhibitor（DMEA or NaNO₂） on one side of concrete sample, weobserved the evolution of anodic current distribution of WBE with inhibitor moleculepenetration, to discuss the different inhibitors’ migration rate on the interface ofelectrode/concrete and the recovery capacity of corroded area.The results show that Fe²⁺ions from a corroding wire electrode diffuse out throughpores in the mortar, then react with OH-ions and O₂in pore solution, forming insolublecorrosion products Corrosion products accumulate mainly in the micro pores along thesteel/mortar interface, the resulting volumetric expansion gives rise to the propagation ofcracks and a further inclusion of aggressive species, which would exacerbate the corrosionof rebar. When corrosion products spread to a vicinal uncorroded（passive） wire electrode, itwould initiate pitting corrosion of the passive wire electrode due to the high Cl-ion levelaround it, since the corrosion products have a strong Cl-ions adsorption and cathodicdepolarization ability；As a migrating corrosion inhibitor, DMEA can penetrate into themicrocrack and capillary channels of concrete quickly during dry and wet cycles and rehabilitate the corroded area; On the contrary, NaNO₂has a low diffusion rate, and itsconcentration is low in the beginning,and can not inhibit the develop of corrosion.