PlanetBox is made of polished steel that will show signs of use after years of faithful service. This is normal and safe. Use of ‘brillo’ pads or wire brushes will scratch the surface. As for getting dented, PlanetBox is made of strong, high quality stainless steel, not the thin tin that old-fashioned metal lunch boxes were made of. It is much more durable. That said if you apply an excessive amount of force it may dent.