Steel roof coatings mostly suffer from corrosion, due to weathering of the exsiting coating. To eliminate this you need a good protective coating product that will give long term protection and low cost maintenance.
Steel roof coating systems can sometimes require a coating system of primer, mid-coat and a finish coat depending on the present condition of the roof. If it is new steel uncoated then you will most probably require a coating system , if it is old coating you may be able to re-coat over, ensuring good surface preparation and compatibility.