Mass transfer analysis considering gas phase diffusion and experimental verification for surface painting a waterborne MCI in concrete

The mass transfer numerical model including the long-term gas phase diffusion of a waterborne migrating corrosion inhibitor (MCI, named PCI-2016) in concrete was investigated in this study. The PCI-2016 was prepared by using multi-compound and chelate-induced techniques. The concentrations of nitrogen in different thickness of cover concrete after surface-painted different amounts of PCI-2016 were calculated by this mass transfer model. The calculated data were basically consistent with the nitrogen contents tested by Kjeldahl method at interface between steel bar and mortar matrix. To verify the anticorrosion performance of painting PCI-2016 steel bars bedded in mortar specimens containing different content of NaCl painted with relevant amounts of PCI-2016 were also investigated by the linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). The results revealed that the I _corr of steel bar in the specimen containing 1.25% NaCl (wt. to cement) after painting with 5 g PCI-2016 for 3 days and 28 days decreased from 0.67 μA·cm ^–2 (before painting) to 0.25 μA·cm ^–2 and 0.06 μA·cm ^–2 , respectively. The numerical analysis and test results supported that the gas phase transfer model is suitable to calculate the weight of PCI-2016 at the interface zone between steel bar and concrete, and the painted the certain amounts of PCI-2016 on the surface of mortar could show an identified repairing effect on the corrosive steel bar.