The corrosion of zinc coatings on buildings is related to the properties of the building materials. For instance, cement and lime mortar have high alkalinity, which can be highly corrosive to zinc coatings. Additionally, during the drying process, water vapor condenses on the surface of the zinc coating, trapping oxygen while preventing the contact of carbon dioxide. This leads to particularly intense corrosion. If cement contains magnesium chloride, the chloride can damage the protective film, accelerating the corrosion of the zinc coating. Asphalt applied to rooftops can produce organic acids under sunlight, which, when in contact with the zinc coating through rainwater, exerts a strong corrosive effect.
On galvanized steel pipes used for transporting warm water and steam, there is usually a layer of thermal insulation material. If the moisture in this material is not easily evaporated, it can easily cause corrosion. For example, when slag wool is used as insulation material, it contains not only a certain amount of moisture but also sulfides, making the corrosion rate of the zinc coating even faster.
