Hydrogen peroxide pickling of stainless steel

A process for removing scale from a ferrous alloy containing chromium, comprising:

• providing a ferrous alloy strip containing chromium covered by scale,
• pretreating the strip to crack the scale,
• immersing the pretreated strip into at least one pickling tank containing an inorganic acid from the group consisting of hydrochloric and sulfuric acid to remove the cracked scale thereby forming a pickled strip, and
• applying an aqueous solution free of dissolved iron containing at least about 20 g/l hydrogen peroxide and at least about 5 g/l of the inorganic acid to the pickled strip wherein any residual scale on the pickled strip becomes activated by the peroxide and simultaneously removed by the inorganic acid contained in the aqueous solution thereby forming a clean strip.

A process for removing scale from a ferrous alloy containing chromium, comprising:

• providing a stainless steel strip covered by scale,
• pretreating the strip to crack the scale,
• immersing the pretreated strip into at least one pickling tank containing at least 50 g/l of inorganic acid at a temperature of at least 77.degree. C. to remove the cracked scale thereby forming a pickled strip,
• applying an aqueous solution free of dissolved iron containing at least about 20 g/l of hydrogen peroxide and at least about 20 g/l of the inorganic acid to activate any residual scale on the strip, immersing the activated strip into another pickling tank containing at least 50 g/l of the inorganic acid at a temperature of at least 77.degree. C. to remove any activated residual scale, and applying the aqueous solution containing at least about 20 g/l of the hydrogen peroxide and at least about 20 g/l inorganic acid to the pickled strip wherein any residual scale on the pickled strip becomes activated by the hydrogen peroxide and simultaneously removed by the inorganic acid contained in the aqueous solution thereby forming a clean strip.