Microencapsulated corrosion inhibitors for controlled release in simulated concrete pore solutions

Colophony microcapsules synthesized by water in oil in water double emulsion containing NaNO₂ corrosion inhibitors were investigated for controlled release in simulated concrete pore solutions. With high encapsulation efficiency of 83% measured by induced coupled plasma optical emission spectroscopy, the microcapsules were introduced to solutions of deionized water (pH 6.8), carbonate bicarbonate buffer solution (pH 9.1), and simulated concrete pore solution made of saturated calcium hydroxide (pH 12.6) to measure the corrosion inhibitor release. Due to the pKa of colophony, the corrosion inhibitors experienced a faster release in alkaline solutions of pH 9.1 and 12.6. Additionally, the corrosion inhibitive performance was determined by electrochemical impedance spectroscopy and potentiodynamic polarization to protect carbon steel rebars from chloride induced corrosion and carbonation.