Performance and Application of Double-layered Microcapsule Corrosion Inhibitors

Abstract

Double-layered microcapsule corrosion inhibitors were developed by sodium monofluorophosphate as the core material, polymethyl methacrylate as the inner wall material, and polyvinyl alcohol as the outer wall material combining the solvent evaporation method and spray drying method. The protection by the outer capsule wall was used to prolong the service life of the corrosion inhibitor. The dispersion, encapsulation, thermal stability of microcapsules, and the degradation rate of capsule wall in concrete pore solution were analyzed by ultra-deep field microscopy, scanning electron microscopy, thermal analyzer, and sodium ion release rate analysis. The microcapsules were incorporated into mortar samples containing steel reinforcement, and the effects of double-layered microcapsule corrosion inhibitors on the performance of the cement matrix and the actual corrosion-inhibiting effect were analyzed. The experimental results show that the double-layered microcapsules have a moderate particle size and uniform distribution, and the capsules were completely wrapped. The microcapsules as a whole have good thermal stability below 230 °C. The monolayer membrane structure microcapsules completely broke within 1 day in the simulated concrete pore solution, and the double-layer membrane structure prolonged the service life of the microcapsules to 80 days in the simulated concrete pore solution before the core material was completely released. The mortar samples containing steel reinforcement incorporated with the double-layered microcapsule corrosion inhibitors still maintained a higher corrosion potential than the monolayer microcapsule corrosion inhibitors control group at 60 days. The incorporation of double-layered microcapsules into the cement matrix has no significant adverse effect on the setting time and early strength.

Keywords

corrosion inhibitors / microcapsule / double-layer structure / potentiodynamic polarization curve

References

[1] Wang RJ, Hu ZY, Li Y, et al. Review on the Deterioration and Approaches to Enhance the Durability of Concrete in the Freeze-thaw Environment[J]. Construction and Building Materials, 2022, 321: 20-25.

[2] Sergey U, Dmitry G, Grigoriy C. Study of Changes in Concrete Durability During the Operation of Buildings[J]. Curved and Layered Structures, 2022, 9: 69-72.

[3] Mao QJ, Feng XJ, Peng L, et al. Characteristics of Self-Healing Microcapsules for Cementitious Composites[J]. Journal of Wuhan University of Technology-Mater. Sci. Ed., 2018, 33: 1108-1112.

[4] Wang X, Ni W, Jin RZ, et al. Formation of Friedel’s Salt using Steel Slag and Potash Mine Brine Water[J]. Construction and Building Materials, 2019, 220: 119-127.

[5] Yohai L, Vazquez M, Valcarce MB, et al. Phosphate Ions as Corrosion Inhibitors for Reinforcement Steel in Chloride-rich Environments[J]. Electrochimica Acta, 2013, 102: 22-29.

[6] Bastidas DM, Criado M, Fajardo S, et al. Corrosion Inhibition Mechanism of Phosphates for Early-age Reinforced Mortar in the Presence of Chlorides[J]. Cement and Concrete Composites, 2015, 61: 365-371.

[7] Shi JJ, Sun W, et al. Effects of Phosphate on the Chloride-induced Corrosion Behavior of Reinforcing Steel in Mortars[J]. Cement and Concrete Composites, 2014, 45: 166-175.

[8] Zeng XG, Gong M, Luo H, et al. Research and Development of Environmentally Friendly Corrosion Inhibitors[J]. Corrosion and Protection, 2007, 28: 147-150.

[9] He YX, Zhu GM, Wu ZP, et al. Preparation of Microcapsule with Chlorine Ion Triggered by Solvent Evaporation Technique[J]. Journal of Functional Materials, 2015, 46: 2144-2147. +2152

[10] Dong BQ, Ding WJ, Qin SF, et al. Chemical Self-healing System with Novel Microcapsules for Corrosion Inhibition of Rebar in Concrete[J]. Cement and Concrete Composites, 2018, 85: 211-216.

[11] Gu J, Li JJ, Sun YP, et al. Progresses in the Modification and Application of Poly(vinyl alcohol) Membrane[J]. Chemical Industry and Engineering Progress, 2013, 32: 1074-1080.

[12] Wang RZ. Study on Preparation and Application of Microencapsulated Corrosion Inhibitor for Reinforcing Steel, 2022 Tianjin: Tianjin Chengjian University. Bar[D]