Electrolytically pickling carbon or low alloy steels - cathodically and anodically in aq soln of iron sulphate

摘要

An electrolytic pickling process for C- or low-alloy steels comprises using the steel for 15 sec. to 15 mins., alternatively as a cathode and anode of an electrolytic cell contg. an aq. soln. of pH 6-8 contg. 0.5-2.5 moles Fe sulphate, the temp. being 30-100 degrees C and the current density for the cell being 5-60 A/dm2. The descaled steel is more resistant to atmospheric oxidation, and the surface remains shiny for long periods. The bath is self-regenerating. Fe in the form of Fe2O3 can be recovered from the slimes composed mainly of Fe hydroxides. All disadvantages relating to the storage and use of acids are avoided. There are no polluting gases evolved. The lift of the plant is extended. Magnetic steels are passivated during anodic pickling and the current is reduced drastically at the end of the process thus avoiding overpickling. The process is useful in the prodn. of flat-plate steel.