| The application prospect of colored stainless steel, principle and the method of its surface—coloring are discussed. The relationships between the color, time and potential as well as the method of sealing method of holes are stated in detail. Chemical coloring of stainless steel has been studied in the solution of 250 g · dm-3 chromium trioxide, 490 g · dm-3 sulphuric acid and some additives at around 70℃. Both the changes of potential and color with time and the relationship between electrode potentials and coloring of stainless steel sample have been found out. This would be helpful with the coloring of stainless steel in reproducibility even if some changes were taken place in temperature or solution composition. The influences of pretreatment, additives and temperatures on the coloring have also been studied.The electrolytic polishing of stainless steel is a key of the pretreatment of coloring stainless steel, thus it has been studied in a solution of 500g 85% H3PO4, 130g 98% H2SO4, 130g 18% aqueous solution of polyethylene glycol. The optimum operation temperatures are 7590℃ and the anodic current densities are 8 15A · dm-2.Colored stainless steel may be prepared in brown, blue, yellow, red, or green by square—wave AC electrolytic coloring in the solution of 250 g · dm-3 chromium trioxide, 490 g · dm-3 sulphuric acid and some additives at around 50℃ . Oxide film in the expected tone of such color can be obtained by controlling current density, square—wave cycle period and number of the repetition cycles.The experiment results show that the samples activated in dilute sulphuric acid and polished by electrolysis have a uniform and bright color, different additives and higher temperature could increase the coloring rate. Polyethylene glycol forms effectively a sticky layer on the surface of stainless steel and improves the brightness obviously. By using a solution free from chromates, this new technology reduced both environment pollution and production cost. The results of a mirror-like appearance have been obtained on the surface of stainless steel. Electrolytic coloring canlower the operation temperature of the solution , reduce the coloring time and make the coloring control easier and reproducibility better. The electrolytic polishing of stainless steel is a key of the pretreatment of coloring stainless steel and directly affects the quality of colored stainless steel. Chemical coloring of stainless steel have satisfactory color uniformity. The coloring speed will increase with addition of manganese sulphate. The results show that the addition of ammonium molybdate can improve coloring brightness, The optimum content is respectively 56g/l manganese sulphate and 68g/l ammonium molybdate. The reproduction of color film needs additives which have obvious potential of coloring according to color matching method. The potential control is useful in industrial application.
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