SCALE REMOVAL METHOD Russian patent published in 2010 - IPC C23G1/08 C23F1/28 

FIELD: metallurgy.

SUBSTANCE: invention related to removal of scale from carbon steel and can be used for flushing processes of heat engineering equipment - steam boilers and communication systems. Method for removing scale from carbon steels involves etching of scale with the solution containing 0.002-0.005 mol/l of EDTA or OEDF complexon, 0.01 - 0.1 mol/l of protonated complex Fe(II) with EDTA or OEDF, 1-2 g/l of sulphuric acid and water, and having pH 2.2 when using EDTA or pH 1.5 when using OEDF, at 60-110 °C and rapid mixing of solution with mixer rotation frequency of 1000 rpm; at that, etching of scale is performed only the solution is blown down with nitrogen or 0.01 g/l of hydrazine or hydroxylamine is added to it.

EFFECT: method provides complete removal of scale from surface of steel equipment at maintaining physic and chemical properties of metal and at increasing removal speed of oxide-salt deposits from surface; at that, waste regenerated solution can be used for many times.

3 dwg, 1 tbl, 4 ex