Cold drawn steel pipe is passivated by pickling

　　The appearance of the cold drawn steel pipe will form a dense oxide film, to prevent the concentrated sulfuric acid or nitric acid to further react with the phenomenon called passivation. An active metal or an alloy, wherein the chemical activity is greatly reduced, and a noble metal state phenomenon, called passivation.

　　Metal generated by the role of the medium due to corrosion products, which has a dense structure, the formation of a layer of film (often invisible tightly covered in the outer of the metal, then change the state of the metal on the outer significantly to the positive direction, so that the electrode potential of the metal transitions become passive corrosion such as FeFe + + when the specification potential transition to +0.51 V-0.44V passivation shows precious metals corrosion performance, this film is called passivation film cold drawn steel pipe chromate solution with Miles hung metal appearance generated trivalent or hexavalent chromium layer, called passivation, Yiming chromium used for the disposal of aluminum, magnesium and their alloys can also form on the steel chromium layer, but rarely used alone, often phosphide and supporting the use of, to close the porosity of the phosphate layer, the phosphating layer bare steel passivation, to inhibit the corrosive effect of the remaining phosphating accelerator, to further increase the protective capacity cold drawn steel pipe passivation Usually using potassium dichromate solution (2 to 4 grams / liter, and sometimes 1 to 2 g of phosphoric acid was added) 80-90 degrees Celsius dip Tut 2-3 minutes to remove.