In this case, the only available valve is the new ceramic ball valve. Hydrochloric acid medium: Most metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel PTFE coated adhesive tapes materials), and high-silicon ferro-molybdenum can only be used in hydrochloric acid below 50°C and 30%. The corrosion of sulfuric acid with different concentrations and temperatures is quite different.
Sulfuric acid medium: As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Nitric acid medium: most metals are quickly corroded and destroyed in nitric acid.For valves under corrosive medium conditions, anti-corrosion is the most critical part of chemical equipment. Therefore, the scientific nature of the material selection should be paid attention to when selecting the chemical equipment. Here are some key points of material selection for some commonly used chemical media: 1. Contrary to metal materials, most non-metal materials have good corrosion resistance to hydrochloric acid, so rubber pumps and plastic pumps (such as polypropylene, fluoroplastics, etc. If the metal materials of chemical valves cannot be selected correctly, a little carelessness can damage the equipment, or cause accidents or even disasters.
For concentrated sulfuric acid with a concentration above 80% and temperature less than 80℃, carbon steel and cast iron have good corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid.) are the best choice for transporting hydrochloric acid.. For high temperature nitric acid, titanium and titanium alloy materials are usually used. According to relevant statistics, about 60% of the damage of chemical equipment is caused by corrosion. It is worth mentioning that stainless steel containing molybdenum The corrosion resistance of nitric acid (such as 316, 316L) is not better than that of ordinary stainless steel (such as 304, 321), and sometimes even worse.
Stainless steel is the most widely used nitric acid resistant material. It has good corrosion resistance to all concentrations of nitric acid at room temperature. It is not suitable for use as a material for pump valves; ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) have limited use for sulfuric acid media. However, when the temperature is higher than 100°C or the pressure is higher than 16 kg, all the functions of the plastic are destroyed. Therefore, pump valves for transporting sulfuric acid are usually made of high-silicon cast iron (difficult to cast and process) and high-alloy stainless steel (alloy 20). Fluoroplastics have good resistance to sulfuric acid, and fluorine-lined pump valves (F46) are a more economical choice. There is usually a misunderstanding that stainless steel is a 'universal material', regardless of the medium and environmental conditions, it is not correct and dangerous
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