Cleaning and descaling of metals. An improved process is described for cleaning, descaling and deoxidation of metals, especially stainless steel. A treating bath acts directly on the scale or oxide itself. Advantages cited are the decrease in time required as compared with the acid‐pickling process, decrease in metal loss to 10 lb./ton, elimination of pickling‐waste disposal problem, reactivity of the bath with C, decreased etching of the metal surfaces, and low cost and simplicity of operation. Thus, in cleaning a Ni‐Cr alloy steel, the complete cycle for satisfactory oxide removal is as follows: 6 to 7 min. in fused NaOH + 5% NaNO3 at 900°F., or 4 to 5 min. at 950°F., water quench, and treatment in 10% HCl at 180° for 1 min. followed by 15 sec. in 15% HNO3 at 180°.—U.S. Pat. 2,678,289, James H. Noble, Rolfe Pottberg and Urlyn C. Tainton.
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