Large roll galvanized wire phosphating film is dark gray to black gray, the thickness is generally 5-20μm, has better corrosion resistance in the atmosphere. Membrane is a microporous structure, strong adsorption ability to paint, such as used as paint bottom, corrosion resistance can be further advanced. Metal oxidation treatment: Add steel products to NaOH and NaNO2 mixed solution, heating treatment, the surface can form a layer of thickness of about 0.5-1.5μm blue oxide film, in order to reach the purpose of steel corrosion prevention, this process is called blue treatment, referred to as blue.