Microstructures and corrosion failure analysis of zinc anode

A corrosion product layer in the thickness of about 1 mm was formed on the failed zinc anode surface, and the non-conducting corrosion product was strongly bonded to the substrate, leading to the failure of anode protection. The corrosion products of zinc anode surface showed the obvious layered structure, which was mostly in flake-like and partly in spherical. The sheet products were mainly Zn₁₂(SO₄)₃Cl₃(OH)₅·5H₂O and Zn₄SO₄(OH)₆·5H₂O, and the spherical products were mainly Zn₅(OH)₈Cl₂·H₂O; the contents of Pb, Cu, and Fe by mass were slightly exceeded standard in the failed zinc block, resulting in the decrease of zinc protection efficiency. If the sacrificial anode was disturbed by stray current, its surface would be deactivated by rapid polarization; when the sacrificial anode was polarized by the constant current of 0.1 mA·cm^-2 for 10 h, the zinc surface would be in polarization passivation state soon, losing the sacrifice protection.