Black plate is a tin mill product which is free of metallic coating. Electrolytic Tin Plate is black plate with an electrodeposited coating of tin. Electrolytic Chrome Coated Steel is black plate that has an electrodeposited coating of chrome and chrome oxides which is, in turn, coated with a lubricating oil.
Oil is applied primarily for lubricity to reduce friction scratches in handling or shearing.
The application of the oil is so light that, in general, one teaspoon of oil can cover the area of a football field. Chemical treatment is a solution containing chrome. It is applied to deposit a chrome-chrome oxide film on the surface of the substrate to increase the corrosion resistance of the product. The total chrome on the surface is measured as weight per area e.g. 300 micrograms per sq.ft. of surface. Customers can order chemical treatment levels within certain ranges from 150 micrograms per sq.