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Metal valve in the atmosphere or solution and other complex working conditions, not only the uniform corrosion of the metal surface occurs all the time, but also the pitting corrosion, crevice corrosion, intergranular corrosion, delamination corrosion, stress corrosion, fatigue corrosion, selective corrosion, wear corrosion, cavitation corrosion, friction corrosion, hydrogen corrosion and other local corrosion in the local position of the metal.

Anticorrosion measures of metal valve

1. Metal surface treatment

Valve connecting bolts are usually treated with zinc plating, chromium plating and oxidation (bluing) to improve the ability of atmospheric and medium corrosion resistance. In addition to the above methods, other fasteners are also treated with phosphating and other surface treatments according to the situation.

Nitriding, boronizing, chromium plating, nickel plating and other surface treatment processes are widely used to improve the corrosion resistance, corrosion resistance and abrasion resistance of the valve stem. Different surface treatment should be suitable for different material and working environment of valve stem. Hard chromium plating and gas nitriding process can be used for valve stem in contact with asbestos packing in atmosphere and water vapor medium (ion nitriding process is not suitable for stainless steel); high phosphorus nickel plating has better protection performance for valve in hydrogen sulfide atmosphere; 38CrMoAlA can also resist corrosion by ion and gas nitriding, but hard chromium plating is not suitable; small diameter valve body and hand wheel are often chrome plated to improve their corrosion resistance and decorate the valve.

2. Thermal spraying

Thermal spraying is a kind of process block for coating preparation, which has become one of the new technologies for material surface protection. It uses high energy density heat sources (gas combustion flame, arc, plasma arc, electric heating, gas explosion, etc.) to heat and melt metal or non-metal materials, spray them on the pretreated basic surface in the form of atomization to form spraying layer, or heat the basic surface at the same time, Most metals and their alloys, metal oxide ceramics, cermet composites and hard metal compounds can form coatings on metal or nonmetal substrates by one or more thermal spraying methods.

Thermal spraying can improve the surface corrosion resistance, wear resistance, high temperature resistance and prolong the service life.

3. Spray paint

Coating is one of the most widely used anti-corrosion means, and it is also an indispensable anti-corrosion material and identification mark in valve products. Coating is also a non-metallic material, which is usually made of synthetic resin, rubber slurry, vegetable oil, solvent, etc., covering the metal surface, The coating is mainly used in water, salt water, sea water, atmosphere and other environment with less strong corrosion. The valve cavity is usually painted with anti-corrosion paint to prevent water, air and other media from corroding the valve. Different colors are mixed in the paint to indicate the materials used by Farne. The valve is usually painted once every six months to a year.