Zinc coating

corrosion protectionwaterproof

Zinc is a unique and very useful nonferrous metal. The largest market for metallic zinc is its usage in high performance, corrosion control coating systems. Zinc is resistant to most atmospheric conditions, yet it remains sufficiently reactive to cathodically protect ferrous metals such as iron and steel. Among the nonferrous metals, zinc is the least expensive and most readily available. While there are other metals that can also be used to protect iron or steel such as magnesium, aluminum and cadmium, none have proven to be as useful, economical or as effective as zinc. In most corrosive atmospheres, when zinc substrates are top coated, they exhibit a much longer service life than the same zinc coating(s) applied over bare iron or steel. ASTM and the Zinc Institute studies demonstrate this. Due to the porosity of the metallizing application and its reactivity to strong acids and caustics, zinc coated iron or steel scheduled for buried service is most effective when sealed or used as a base for a topcoat. In the electrochemical series, zinc is a less noble metal than iron; it has a more negative electrode potential. If zinc is in conductive contact with iron, and an electrolyte such as water is present, the zinc ions go into solution. Again, in electrochemical terms, the exposed surface of the iron forms a cathode, and the zinc-coated surface of the pipe forms an anode. Zinc ions migrate to the damaged point and form a layer of “scarring,” which stops the corrosion.