Effect of zinc particle morphology on the corrosion protection performance of zinc-rich epoxy coatings

The effect of zinc particle morphology and crystallographic orientation on the performance of zinc-rich epoxy coatings (ZRCs) was investigated in this study. Two coatings, one containing commercial spherical zinc (ZRC-CB) and the other one containing treated zinc (T-ZRC-CB) synthesized through a controlled melt-recrystallization process, were formulated with identical zinc and carbon black contents to assess the role of zinc morphology in corrosion protection. XRD results showed that the treated zinc exhibited a higher exposure of active crystallographic planes. As a result, OCP measurements showed that the T-ZRC-CB coating exhibited faster zinc activation and maintained cathodic protection for nearly 70 days, substantially longer than the 10 days cathodic protection provided by ZRC-CB coating. Rust creep evaluation after 30 days of salt spray exposure further demonstrated improved performance, with the T-ZRC-CB coating showing a reduced rust creep of 1.3 mm compared with 2.6 mm for the ZRC-CB coating. EIS measurements also confirmed the enhanced activity of the treated zinc and the better barrier performance of the T-ZRC-CB coating at the end of the experiment. • Zinc with a different morphology produced by a controlled high temperature process • Treated zinc particles contain more exposed active planes. • Epoxy coating with treated zinc showed enhanced corrosion protection performance.