Pickling and passivation of 304 stainless steel tubes
Stainless steel tube because of its good mechanical properties, high hardness and high wear resistance and other advantages are widely used in military products parts processing. The surface treatment of this material is carried out after the solid solution aging of heat treatment. Due to the relatively thick oxide skin and the inherent particularity of the material in the process of heat treatment, it is very difficult to carry out the pickling and passivation processing, so it is necessary to have good products.
The surface treatment process of stainless steel tube is simple. However, in the actual processing process, pickling and passivation processing is quite difficult, mainly in the following two aspects:
(1) stainless steel tube material can not be used to remove the surface oxide skin of parts by the conventional stainless steel derusting method. This paper introduces the application of stainless steel pickling to remove the oxide skin.
(2) the passivation process of the material will not corrode the material in the air, and damage the size and surface finish of the parts, but in the process of processing must be used such a strong oxidant as pickling passivation to produce a passivation film on the surface of the parts, in order to achieve anti-corrosion. Removal of the oxide coating after heat treatment: there are mainly Ti, Cr, Ni, Si, V, Mn, Mo and other elements in stainless steel. These elements form thick and dense oxide coating in the process of heat treatment, and can be composed of iron, chromium, nickel and oxygen to form a spinel structure of the dense oxide film (FeCrO4), the chemical properties are also very stable. Therefore, it is difficult to remove the oxide film.