Pickling passivation of stainless steel pipes

Because of its excellent mechanical properties, high wear resistance and high hardness, the stainless steel pipe has been widely used in the processing of stainless steel pipes for military products. The surface treatment of stainless steel pipe is carried out after heat treatment, solid solution and aging, because the heat treatment process will produce thicker oxide skin and the particularity of the material itself, so it is difficult to do the pickling passivation process.

Pickling passivation process

Stainless steel pipe surface treatment process flow is relatively simple. But in actual processing, the difficulty of pickling passivation process is relatively large, generally divided into two aspects: on the one hand, stainless steel pipe can not be removed by ordinary derusting method to remove stainless steel pipe surface oxide skin.

On the other hand, the passivation process of stainless steel pipe material meets the air will not corrode and damage size and surface finish, but in the process it must use pickling passivation strong oxidant to make this stainless steel pipe produces a passivating film on the surface, so as to achieve the purpose of anti corruption. Remove oxide after heat treatment: Ti, Ni, Cr stainless steel, Si, V, Mn, Mo and other elements, these elements will form a thick and dense oxide in the heat treatment process, and can be made of iron, chromium, nickel and oxygen to form a dense oxide film has a spinel structure the (FeCrO4), the chemical nature of the relatively stable. So it is not easy to remove the oxide film.

Stainless steel pipe for low temperature solidification and aging

The stainless steel pipe with low temperature and solid aging is thinner and usually pale purple. It is easier to handle the oxide scale of the stainless steel pipe. Stainless steel pipe by pickling and passivation of stainless steel after pickling, the surface oxide skin will generally clean and no corrosion of stainless steel pipe, stainless steel pipe surface without hanging ash, can be directly used for subsequent passivation processing.

Stainless steel pipe for high temperature solid melting and aging

High temperature solid aging stainless steel pipe has a thick oxide skin, usually black purple, even black. Because the stainless steel pipe surface generates thicker, dense and complex oxide skin, so stainless steel pipe pickling oxidation skin to be more complex. The removal of this kind of oxide skin should be carried out according to the steps of loosening oxide scale, pickling and removing dust.

After loosening the oxide scale, the surface of the stainless steel pipe is often adhered with a layer of ash, and the oxide scale is removed after removing the dust.

The operation process of removing dust is passivation process. The corrosion resistance of stainless steel pipe after pickling is poor in air. If exposed to air, the surface of stainless steel pipe will rust. In order to enhance the corrosion resistance of stainless steel pipe, a compact and corrosion resistant passivation film must be produced on the surface of the stainless steel pipe, so as to achieve the purpose of corrosion resistance. The quality of the passivation film will directly affect the service life and appearance of the stainless steel pipe, and the main factors affecting the quality of the passivation film are the composition of the material and the quality of the passivation solution.

Source: China Stainless Steel Pipe Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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