Galvanized Steel Sheet Corrosion

               Depending on the applications, steel sheet will need to have an extra layer of protection to help defend corrosion that naturally occurs over time. In order for manufactures and distributors of steel products to ensure the material they are using in their projects will last, the steel is often galvanized. Galvanization is done via a hot dipping method, coating the product in a layer of Zinc.  While the protective coating is designed to further safe-guard the steel sheet’s future, corrosion is a process that is hard to fully avoid. galvanized steel sheet is still susceptible to corroding – whether that be because of natural, chemical or electrochemical conditions.

                The degree and speed of a steel product’s corrosion depends on a few factors – though in the majority of cases will gradually occur overtime.  The type of steel, the thickness of protective Zinc on the steel sheet, and the product’s environment all play major roles in steel sheet corrosion.

Natural Corrosion

              Galvanized steel sheet that has is exposed to the atmosphere and rainwater is likely to corrode overtime. The product develops a natural carbonate on it that becomes brittle and will eventually crack and split. The split exposes a new layer of zinc that will corrode, and it can even corrode enough to expose the base layer of steel to the atmosphere and its elements. 

Chemical Corrosion

               Steel sheet that has been galvanized has the ability to resist corrosion from a number of chemicals it comes into contact with including concrete, lead, tin and aluminum. However there are some chemicals that will reduce the products’ protection to corrosion: plaster and cement with chlorides and sulfates, acidic rainwater runoff, zinc plate condensation, moss, lichen, and pooled water on the exterior of the zinc coating.

Electrochemical Corrosion

              Certain electrolytes that come into contact with the zinc layer on galvanized steel sheet can cause an electrolytic reaction.  Some electrolytes that could have an effect include rain, fog, condensation and dew. In order to avoid the reaction, prevent contact between the galvanized steel sheet and electrolytes as much as possible. Another solution is applying paint to the galvanized product to thwart corrosion of the coating of zinc.