Improvements in the object of the principal patent No. 530,241 filed on March 2, 1984, by: a method for protecting flat-rolled

摘要

An improved process for the protection of flat rolled steel sections in the form of bands, plates or sheets in particularly aggressive environments is disclosed. According to applicant's copending U.S. patent application Ser. No. 585,856, filed Mar. 2, 1984, U.S. Pat. No. 4,520,077, steel plates previously plated with zinc or zinc alloys are, as such, plated with layers of an electrolytic plating consisting of inorganic elements or compounds, preferably chromium metal and chromium oxide. The improvement according to this invention comprises a chemical passivation in a chrome anhydride solution of the zinc base plating layer, prior to carrying out the successive multi-layer electrolytic plating of inorganic elements or compounds.