Study On Removement Of The Oxide Layers And Polishing From The Surface Of 304 Stainless Steel By Mixed Acid With No-Chromium

304 stainless steel is commonly used in the industry and life, to structural materials,because of its better corrosion resistance, easy processing, but in the long-term machining process, the surface is easily oxidized and forming a layer of loose, uneven film, which make it easier for stainless steel corrosion, shorten service life.This paper selects 304 stainless steel as the research object, using microscopic methods?SEM, EDS? analysis before and after the experiment on the surface of the oxide film, found that the main components are the oxide of iron, chromium and nickel,study on the conditions of removing the oxide layers by chromium free mixed acid method, the formulation of the oxidant, acid ingredients, additives, complex, temperature and time were the combination of orthogonal test and selected, the optimal process conditions are obtained. The main components: H₃PO₄80ml/l, HCl120ml/l, Na NO370g/l;the complex: NH₄Cl10g/l, oxalic acid 5g / L; additives for 30ml/l, mainly for brightening agent, corrosion inhibitor and solubilizer; operating temperature of 85?, time for 8min.Found in the experiment that the initial rough degree also affect the removal of rate and polishing effect, and 3D microscopy was used to studied the influence of roughness, It is found that the initial roughness increases, the removal of oxide film on the faster, better polishing effect, in addition, the effect is better by the combination of mechanical and chemical methods such as grinding, ultrasonic etc.. The formula of the prescription and traditional chromic acid and hydrogen peroxide formula were compared and found polishing effect is basically the same by gravimetric analysis, analysis of surface roughness and reflectivity analysis, but the removal rate of the oxide film is about 1000 times higher.Electrochemical testing auxiliary chemical method to study the main ingredient in the formula, oxidation agent to change the structure of the oxide film on the surface of the stainless steel, the loose, peeling, other acid, such as hydrochloric acid is mainlyerosion, the rupture, and then peeled off, phosphoric acid and other adding agent can speed up the removal rate and form a new passivation film, polishing, improve the degree of leveling. In order to get better removal rate and polishing effect, it also explores the oxidizing agent, other additives, process cost and the service life of the polishing liquid.Improvement of 304 stainless steel polishing process cost is lower than traditional chromic acid and hydrogen peroxide solution, formula polishing area is about 1.875 x10^-2 m² / L.