Self-repairing oxides to protect zinc: Review, discussion and prospects

Zinc is protected in the short term by chromate conversion coatings. The Cr (VI) based surface layer has the unique ability to self-repair which is attributable to the aqueous properties of its constituent ions. The thermodynamic feasibility of achieving chromium-like protection for the short term using other candidates is reviewed. Long-term protection of zinc is naturally affected by its own corrosion products (patina), which form a multilayered structure. The role of this patina in protecting the underlying metal is also reviewed, and processes within the patina, including the interaction between its various layers, are elaborated and discussed.