Abstract: A pickling process designed for pickling a metal strip such as a stainless steel strip reduces the amount of HF and/or HNO3. The strip is immersed in at least one first pickling tub that contains a mixture of an acid such as H2SO4, an excess of at least one oxidizing agent, and includes electrodes that may apply a current to the strip that runs through the mixture.

Abstract: The present invention relates to a modular analyzer system for the analysis of at least two or more chemical components contained in pickle liquor solution. The analyzer modules include a strong acid analysis module, a weak acid analysis module, an oxidizer analysis module, and a metal ion analysis module. These four modules may be used in any combination, including the use of more than one of the same type of analysis module.

Abstract: A process for removing scale from stainless steel using an aqueous solution containing hydrogen peroxide and an inorganic acid, i.e., hydrochloric or sulfuric acid. A hot rolled or annealed stainless steel strip (10) covered with scale is immersed into hot inorganic acid contained within pickling tanks (12) and (14). Thereafter, the strip may have residual amounts of tightly adherent scale (11). This scale is activated by a solution containing the inorganic acid and hydrogen peroxide applied to the strip such as by a spray header (16) extending completely transversely across and positioned above the strip and another spray header (18) extending completely transversely across and positioned below the strip. It may be desirable to pass the activated strip through the hot inorganic acid again and reactivate the strip at very high line speeds to insure complete removal of scale from the strip. Any hydrogen peroxide spray dripping from the strip is collected on a catch pan (30) and flowed into a tank (28).

Abstract: A process for removing scale from stainless steel using an aqueous solution containing hydrogen peroxide. A hot rolled or annealed stainless steel strip (10) covered with scale is immersed into hot sulfuric acid contained within tanks (12) and (14). Thereafter, the strip may have residual amounts of tightly adherent scale (11). This scale is activated by the aqueous solution containing hydrogen peroxide applied to the strip such as by a spray header (16) extending completely transversely across and positioned above the strip and another spray header (18) extending completely transversely across and positioned below the strip. Any peroxide spray dripping from the, strip is collected on a catch pan (30) and flowed into a tank (28). Preferably, the peroxide solution is a dilute concentration of the acid in tanks (12) and (14). The hydrochloric acid removes smut from the strip formed by the sulfuric acid to improve the cleanliness of the pickled strip.

Abstract: Acid concentrations are determined by the method and apparatus, particularly HCl acid for picking ferrous material. Specific gravity measurements are made on acid samples, diluted acid samples and water. Conductivity measurements are conducted on the diluted acid samples. The water dilution minimizes the influence of the metal salt in the sample to improve the conductivity measurements. The system calculates the acid concentration by a series of approximations using the conductivity data and the acid concentration - conductivity relationships to provide an accurate acid concentration which is easily automated by computer.

Abstract: Caustic dezincing galvanized steel scrap. A dezincing plant includes a plurality of tanks interconnected in series with steel scrap sequentially being moved through each of the tanks. The tanks contain a caustic leaching solution including an oxidant with the leaching solution being circulated through each of the tanks in a direction opposite to the movement of the scrap. Fresh scrap initially is exposed to a partially depleted leaching solution with the oxidant concentration of the leaching solution increasing as the scrap moves through the series of tanks. Leaching solution depleted of its oxidant is transferred to an electrolytic cell where zinc is removed and plated as metallic zinc powder onto a cathode. The leaching solution is recycled by removing zinc. The chemistry of the leaching solution is controlled so that sufficient free caustic is present to prevent passivating zinc coating on the scrap.