Corrosion of metal needle valve

The corrosion of needle valve is generally understood as the damage of metal material of needle valve under the chemical or electrochemical environment Because the phenomenon of "corrosion" appears in the spontaneous interaction between metal and surrounding environment, how to separate metal from surrounding environment or how to use more non-metallic synthetic materials is the focus of anti-corrosion The valve body (including the bonnet) of needle valve occupies most of the weight of the valve, and it is in frequent contact with the medium, so the selection of valve usually starts from the valve body material There are two kinds of corrosion of valve body, chemical corrosion and electrochemical corrosion Its corrosion rate depends on the temperature, pressure, chemical properties of the medium and the corrosion resistance of the valve body material Corrosion rate can be divided into six grades: 1 Complete corrosion resistance: corrosion rate is less than 0.001 mm / year; 2 Extreme corrosion resistance: corrosion rate is 0.001-0.01 mm / year; 3 Corrosion resistance: corrosion rate is 0.01-0.1 mm / year; 4 Corrosion resistance: corrosion rate is 0.1-1.0 mm / year; 5 Poor corrosion resistance: corrosion rate is 1.0-10 mm / year; 6 Non corrosion resistance: corrosion rate is more than 10 mm / year.