How To Test The Material Of Barbed Wire?
How to test the material of Barbed Wire?
1. The necessity of pickling passivation of wire mesh:
Austenitic Barbed Wire has good corrosion resistance, high temperature oxidation resistance, good low temperature performance and excellent mechanical and added r energy. So widely used in chemical, oil, power, nuclear engineering, aerospace, marine, pharmaceutical, light industry, textile and other departments. Its main purpose is to rust and rust. The corrosion resistance of the wire mesh depends mainly on the surface passivation film, if the membrane is incomplete or defective, Barbed Wire will still be corroded. Engineering is usually carried out pickling passivation treatment, so that the corrosion resistance of Barbed Wire to play even greater. In the process of forming, assembling, welding, weld inspection (such as flaw detection, pressure test) and construction marking in the process of wire mesh equipment and components, it brings surface oil, rust, non-metallic dirt, low melting metal pollutants, Slag and spatter, etc. These materials affect the surface quality of wire mesh equipment and components, destroy the oxide film on its surface, reduce the overall corrosion resistance of steel and local corrosion resistance (including pitting, crevice corrosion), and even lead to Stress corrosion cracking.
Barbed Wire surface cleaning, pickling and passivation, in addition to maximize the increase in corrosion resistance, but also to prevent product contamination and get a beautiful role. In GBl50 a 1998 "steel pressure vessel" provides that "anti-corrosion requirements of the wire mesh and composite steel plate made of the surface of the container should be pickled passivation." This requirement is for the use of pressure vessels in petrochemical industry, because these devices are used in direct contact with the corrosive medium, from the guarantee of corrosion resistance and corrosion resistance, the proposed pickling passivation is necessary. For other industrial sectors, if not for corrosion purposes, only based on clean and beautiful requirements, and the use of Barbed Wire is no need for pickling passivation. But the wire mesh equipment, welding also need to pickling passivation. On the nuclear engineering, some chemical equipment and other demanding use, in addition to pickling passivation, but also the use of high-purity medium for the final fine cleaning or mechanical, chemical and electrolytic polishing and other finishing.
2. Iron wire pickling passivation principle
The corrosion resistance of the wire mesh is mainly due to the surface covered with a very thin (about 1nm) dense passivation film, which film 1n corrosive media isolation, is the basic barrier of wire mesh protection. Barbed Wire passivation with dynamic characteristics, should not be seen as corrosion completely stopped, but the formation of the diffusion barrier, so that the anode reaction rate greatly reduced. Often in the presence of a reducing agent such as chloride ion, it tends to break the membrane and retain or repair the membrane in the presence of an oxidizing agent such as air.
Barbed Wire placed in the air will form an oxide film, but the protection of this film is not perfect. Usually must be thoroughly cleaned, including alkaline washing and pickling, and then passivation of oxidants in order to ensure the integrity and stability of the passivation film. One of the purposes of pickling is to create favorable conditions for passivation treatment to ensure the formation of high quality passivation film. Because the surface of the Barbed Wire by an average of 10μm thick layer of surface corrosion is corrosive, acid chemical activity makes the defect site of the dissolution rate higher than other parts of the surface, Barbed Wire so pickling can make the whole surface tends to even balance, some of the original Easy to cause corrosion hazards were cleared. But more importantly, through the pickling passivation, so that iron and iron oxide than chromium and chromium oxide given priority to dissolve, remove the chromium layer, resulting in chromium in the Barbed Wire mesh surface enrichment, this chromium-rich passivation film Of the potential up to + 1.0 V (SCE), close to the potential of precious metals, improve the stability of corrosion resistance. Different passivation treatments also affect the composition and structure of the film and thus affect the rust, such as by electrochemical modification, allowing the passivation film to have a multilayer structure, forming CrO3 or Cr2O3 in the barrier layer, or forming a glassy Of the oxide film, so that Barbed Wire can play the greatest corrosion resistance.