Using a zinc coating to protect the underlying steel substrate from corrosion, or to minimize its exposure to corrosion, has proven to be highly effective in general atmospheric conditions. The principles of its corrosion protection mainly involve the following aspects:
(1) A thin and dense layer of zinc oxide forms on the surface of the zinc coating. This zinc oxide layer is difficult to dissolve in water, thus providing a certain degree of protection to the underlying zinc layer. However, when its thickness reaches around 300 nanometers, it becomes prone to detachment. If zinc oxide reacts with other components in the atmosphere to form insoluble zinc salts, the corrosion protection effect becomes even more ideal.
(2) The zinc coating serves as a dense thin film covering the steel surface, preventing the steel substrate from coming into contact with any corrosive solutions and thus protecting it from corrosion.
(3) In the event that small areas of the steel substrate are found to be uncoated or partially exposed due to corrosion, the zinc coating can form an iron-zinc galvanic microcell under the electrolytic conditions created by the surface water film. This allows the adjacent zinc layer to repair the uncoated and exposed areas, continuing to provide protective effects.
