Protective primers with reduced zinc powder content caused by the addition of core-shell micro talc/polyaniline pigment

Abstract

This study aims to verify the possibility of replacing a portion of zinc (up to 30 wt.%) with a newly designed micro talc/polyaniline (PANI) core-shell pigment that can be used in the protective primer compositions for metals. Measurements of the electrode potential of painted steel and the electrical capacity of the steel/coating/electrolyte system showed that synthesized pigment bears two functions. Firstly, its presence in the epoxy-amine coatings provides a cathodic protection mechanism for steel with the lower zinc content. Secondly, it allows long-term preservation of the sacrificial metal activity and passive state of the substrate due to the autocatalytic redox cycle based on the reversible conversion of PANI from its emeraldine to leucoemeraldine form. The corresponding mechanism that allows the retaining of sacrificial metal activity and the passive state of the substrate is proposed.