About Galvanized iron roofing installation

Galvanized iron is iron coated with zinc, the object being to protect its surface from the rapid oxidation taking place when it is exposed to atmospheric influences. The zinc coating is applied to the plates while they are heated, the plates being previously prepared by cleaning and dipping in various chemical solutions, as sulphuric acid, and the salts of chloride of zinc, or sal ammoniac. The coating should be of uniform thickness and should cover the entire surface.

To test the quality of galvanized iron, make a double seam and mallet it down close; if it shows no fracture the iron is of a good quality. A more severe test is to again flatten out the joint or seam so made, without the material showing fracture. Samples may be tested for thickness of coating by greasing them and holding them over a gas jet with a pair of pliers; the amount of fusible metal flowing off will determine the character of each sample.

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