Roofing Sheet / prepainted gi steel coil / ppgi / color coated galvanized steel sheet in coil. Galvanized steel is steel that has gone through a chemical process to keep it from corroding.The steel gets coated in layers of zinc oxide because this protective metal does not get rusty as easily.The coating also gives the steel a more durable ,hard to scratch finish that many people find attractive.For countless outdoor,marine,or industrial applications, galvanized steel is an essential fabrication component.