Coating of Stainless- and Carbon-Steel Foil

Ceramic coatings developed for application to alloy metals and other coatings developed for ingot iron and low carbon steel were successfully applied to specimens cut from .002 inch thick sheets of Inconel, Nichrome, 18-8 stainless-steel types 321 and 347 and to carbon steel, respectively. Scouring the metal surfaces with coating slip, followed by washing and drying, proved to be a satisfactory method for preparing the alloy metals for coating. A ten- minute anneal at 1800 F improved the adherence of the coatings to the metal, particularly in the cases of the Inconel and Nichrome foils which had polished surfaces. Scouring and pickling were both found to be satisfactory methods for the preparation of the carbon steel foil. With extended heating at 1900 F all uncoated alloy specimens showed some oxidation, as evidenced by a reduction in cross sectional area. Similar specimens, protected by refractory ceramic coatings, showed little or no reduction in metal thickness. Complete oxidation of the uncoated carbon steel foil occurred after 17 hours at a temperature of 1400 F while coated specimens withstood a total of 64 hours at temperatures up to 1600 F.