Electrochemical and DFT Study of NaNO2/NaNO3 Corrosion Inhibitor Blends for Rebar in Simulated Concrete Pore Solution

Coatings

Karl Breimaier¹  Ulises Martin¹  Jacob Ress¹  David M. Bastidas¹ 

[1] National Center for Education and Research on Corrosion and Materials Performance, NCERCAMP-UA, Department Chemical, Biomolecular, and Corrosion Engineering, The University of Akron, Akron, OH 44325-3906, USA;

关键词: reinforcement corrosion protection;    electrochemical kinetics;    potentiodynamic polarization;    EIS;    density functional theory;    activation energy;   

DOI  :  10.3390/coatings12060861

来源: DOAJ

【 摘 要 】

The use of nitrite- and nitrate-based inhibitors provides corrosion protection by the development of passive oxide film on the metal surface in reinforced concrete applications. However, the impact of the nitrite and nitrate ratio in the mixture has not been widely studied. In this study, the corrosion protection provided by NaNO₂:NaNO₃ inhibitor blends with ratios of 0.5:1, 1:1, and 1:0.5 were studied to maximize corrosion inhibition efficiency. The nitrite species imparted higher corrosion protection, as shown by cyclic potentiodynamic polarization, with an i_corr of 1.16 × 10^–7 A/cm² for the 1:0.5 mixture, lower than for both the 1:1 and 0.5:1 mixtures. Electrochemical impedance spectroscopy was also performed, with the 1:0.5 mixture consistently displaying high resistance values, showing an R_ct of 1.31 × 10⁵ Ω cm². The effect of temperature was also assessed; the E_a’s of the corrosion reaction were calculated to be 12.1, 9.2, and 4.9 kJ/mol for the 0.5:1, 1:1, and 1:0.5 (NO₂⁻:NO₃⁻) mixtures, respectively. Density functional theory was applied to analyze the molecular properties and to determine the relationship between the quantum properties and corrosion inhibition. The ΔE of NO₂⁻ was found to be −5.74 eV, lower than that of NO₃⁻ (−5.45 eV), corroborating the experimental results. Lastly, commercially available inhibitor mixtures were investigated and nitrite/nitrate concentrations determined to evaluate their corrosion protection performance; amongst the two inhibitor blends tested, Sika was found to outperform Yara due to its greater NO₂⁻ concentration.

【 授权许可】

Unknown