Hot Rolled material comes with the “SCALE” still on the base metal. Scale is composed of oxides that form on the hot metal during rolling and cooling. Pickled and Oiled material has the scale removed by an acid process and then oiled to protect from rust. Cold rolled material has had the scale removed by a chemical process and further “ROLLED” to get a consistent finish. The cold rolled material comes in a number of finishes from dull, or commercial grade to bright, or plating quality.