Ultrasound assisted synthesis of calcium zinc phosphate pigment and its application in nanocontainer for active anticorrosion coatings

• Ultrasound assisted synthesis of calcium zinc phosphate nano pigment demonstrated.
• LbL assembly of calcium zinc phosphate nanocontainers have been achieved.
• Improvement in the anticorrosion properties of coatings due to the nanocontainers.

The present work deals with the loading and responsive release of corrosion inhibitor (benzotriazole) on polyelectrolyte layer in the case of anticorrosive nano pigment calcium zinc phosphate [CaZn2(PO4)2] prepared by layer-by-layer (LbL) method. Synthesis of CaZn2(PO4)2 and the encapsulation of polyaniline (PANI) on nano CaZn2(PO4)2 and LbL assembly of nanocontainers has been achieved using ultrasonic irradiation. Formation of small/uniform particle size of nanopigment and complete encapsulation of polyelectrolyte on the pigment has been observed mainly due to the presence of ultrasonic irradiations during the preparation process. The release of benzotriazole from CaZn2(PO4)2 nanocontainer have been quantitatively evaluated in water at different pH. With an increase in the percent loading of CaZn2(PO4)2 nanocontainer from 0 to 4%, the corrosion rate has been found to be decreased from 2.2 to 0.15 mm/y respectively in 5% HCl. Corrosion potential values are found to be shifted to positive side from −0.62 to −0.485 V with the addition of 4 wt.% of CaZn2(PO4)2 nanocontainers in the alkyd resin. Results of corrosion rate analysis, Tafel and Bode plots of nanocontainer coatings on mild steel panel showed significant improvement in the anticorrosion performance of the nanocontainer/alkyd resin coatings.