Benzotriazole encapsulation in spray-dried carboxymethylcellulose microspheres for active corrosion protection of carbon steel

•Carboxymethylcellulose microspheres containing BTA corrosion inhibitor were prepared by spray drying technique in one step.•The smart release of corrosion inhibitor (BTA) from the microspheres rendered active protection to carbon steel under aggressive conditions.•The corrosion inhibition properties imparted by the biopolymeric microspheres is associated with a high burst inhibitor release capacity.•An environmentally-friendly microcontainer was obtained and can be used in the development of smart anticorrosive coatings. Biopolymeric microspheres containing corrosion inhibitor benzotriazole (BTA) were prepared by a spray-drying technique using carboxymethylcellulose (CMC-Na) as encapsulating material. The resulting microspheres were characterized by FTIR, TGA, SEM and TEM analysis. Microspheres containing BTA have an average diameter of 1.1 μm. FTIR analysis confirmed the presence of the core and encapsulating components. The release studies by UV−Vis spectrophotometry showed that the mechanism of inhibitor release from CMC-Na biopolymeric matrix is based on a hydrogel-swelling-driven mechanism triggered by water presence. Electrochemical impedance spectroscopy (EIS) measurements on bare carbon steel in NaCl solution revealed that the presence of CMC-Na does not affect the corrosion inhibition mechanism associated with BTA. Furthermore, the microcapsules were added to an epoxy coating and its active corrosion protection performance was also investigated by EIS. The results obtained indicate that capsules loaded with BTA do not affect negatively the barrier properties of the coating, and contribute for the enhancement of the corrosion protection of the metallic substrate. Therefore, this work shows the potential application of carboxymethylcellulose microspheres for development of new environmentally-friendly microcontainers for corrosion inhibitors.