Pickling and Passivation of Stainless Steel Pipes-Shangzhan stainless steel

Stainless steel is widely used in parts processing of military products because of its good mechanical properties, high hardness and high wear resistance.The surface treatment of this material is carried out after solution and aging of heat treatment. Because of the thick oxide scale and the inherent particularity of the material caused by heat treatment, it is very difficult to carry out acid pickling and passivation. It is necessary to have a good product 1 acid pickling and passivation process. The process of surface treatment and processing of stainless steel is simple.However, in the actual processing process, acid pickling passivation processing is quite difficult, mainly concentrated in the following two aspects: (1) stainless steel materials can not be removed according to the conventional stainless steel rust removal method, the stainless steel acid pickling oxide scale removal applicable to this material is introduced.(2) The passivation process material of this material will not corrode and destroy the size and surface finish of the parts when it meets the air. However, in the process of processing, it is necessary to use strong oxidant such as pickling and passivation to generate a passivation film on the surface of the parts in order to achieve corrosion resistance.Removal of oxide scales after heat treatment: Ti, Cr, Ni, Si, V, Mn, Mo and other elements are the main elements in stainless steel. These elements form thicker and denser oxide scales during heat treatment, and can form a dense oxide film (FeCrO4) with spinel structure from iron, chromium, nickel and oxygen. Its chemical properties are also stable.Therefore, it is not easy to remove the oxide film.2.1.1 The oxide scales of the parts aged at low temperature are thin and usually light purple. It is relatively easy to treat the oxide scales of the parts aged at low temperature.After the parts are pickled and passivated according to stainless steel pickling, the oxide scale on the surface has been basically removed, and the parts are not corroded, and the surface of the parts is free of ash, so the subsequent passivation processing can be carried out directly.2.1.2 For the parts aged by high temperature solid melting, the oxide scale of the parts aged by high temperature solid melting is thicker, usually black purple or even black.Because of the thicker, denser and more complex oxide scales formed on the surface of parts, the removal of oxide scales by acid pickling of such parts is relatively complex.Removal of this kind of oxide skin should be carried out according to the steps of loosening oxide skin, pickling and removing hanging ash.(1) loosening oxide skin: (2) pickling operation: after loosening oxide skin, the surface of parts often adheres to a layer of hanging ash, after removing hanging ash, the oxide skin is passivated.(3) The operation procedures of removing hanging ash are as follows: the parts pickled by passivation process have poor corrosion resistance in air, and if exposed to air, the surface of the parts will rust.In order to enhance the corrosion resistance of parts, a dense passivation film with good corrosion resistance must be formed on the surface of parts to achieve the purpose of corrosion resistance.The quality of passivation film will directly affect the service life of parts and product appearance. The main factors affecting the quality of passivation film are the composition of materials and the quality of passivation solution.