The particle size effect of MALPB-DEA dispersions on their anticorrosion performances as waterborne coatings on galvanized sheet

Maleic anhydride-g-liquid polybutadiene (MALPB) dispersions were prepared by chemical modification with diethanolamine (DEA) during direct polymer emulsification, and their anticorrosion performances on galvanized sheet were found to be strongly dependent on their particle size and distribution with the variation of DEA. The dispersion containing DEA to maleic anhydride at molar ratio of 2:1 exhibited much smaller particle size and narrower size distribution than that containing DEA to maleic anhydride at molar ratio of 1:1, as measured by a laser diffraction particle size analyzer. A more compact organic layer was supposed to be formed by the dispersion composed of smaller size and narrower size distribution particles on the galvanized sheet, which exhibited better anticorrosive properties. This compact layer slowed down the electrolyte penetration onto the metal surface such that the life span of the metal could be prolonged, which was reflected in the increase in corrosion potential as measured by DC polarization, higher impedance during immersion in 3.5 wt% NaCl solution as measured by electrochemical impedance spectroscopy (EIS), and improved durability in harsh environment as observed by images after salt spray tests.