Corrosion has always been one of the hazards of chemical equipment headaches, with slight carelessness ranging from damage to accidents and even disasters. According to relevant statistics, about 60% of the damage to chemical equipment is caused by corrosion. Therefore, when selecting chemical valves, the first thing to pay attention to is the scientific selection of materials. There is usually a misconception that stainless steel is a "material", and it is a great mistake to hold stainless steel valves regardless of the medium and environmental conditions.

The material of chemical valves should be analyzed based on the different media and specific problems, and cannot be cut across all. Here are some key points for selecting materials for commonly used chemical media:

sulphuric acid

As one of the highly corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. The corrosion of materials varies greatly with different concentrations and temperatures of sulfuric acid. For concentrated sulfuric acid with concentrations above 80% and temperatures below 80 ℃, carbon steel and cast iron have good corrosion resistance, but they are not suitable for high-speed flow of sulfuric acid and are not suitable as materials for pump valves; Ordinary stainless steels such as 304 (0Cr18Ni9) and 316 (0Cr18Ni12Mo2Ti) are also limited in their use for sulfuric acid media. Therefore, pump valves for transporting sulfuric acid are usually made of high silicon cast iron (with high difficulty in casting and processing) and high alloy stainless steel (alloy 20). Fluoroplastics have good sulfuric acid resistance, and using fluorine lined valves is a more economical choice.

hydrochloric acid

The vast majority of metal materials are not resistant to hydrochloric acid corrosion (including various stainless steel materials), and high silicon iron containing molybdenum can only be used for hydrochloric acid below 50 ℃ and 30%. Contrary to metal materials, the vast majority of non-metallic materials have good corrosion resistance to hydrochloric acid, so lined rubber valves and plastic valves (such as polypropylene, fluoroplastics, etc.) are better choices for transporting hydrochloric acid.

nitric acid

Most metals are rapidly corroded and destroyed in nitric acid. Stainless steel is a widely used nitric acid resistant material that has good corrosion resistance to all concentrations of nitric acid at room temperature. It is worth mentioning that stainless steel containing molybdenum (such as 316, 316L) not only has no better corrosion resistance to nitric acid than ordinary stainless steel (such as 304, 321), but sometimes even worse. For high-temperature nitric acid, titanium and titanium alloy materials are usually used.

acetic acid

It is one of the highly corrosive substances in organic acids. Ordinary steel will severely corrode in all concentrations and temperatures of acetic acid. Stainless steel is an excellent acetic acid resistant material, and 316 stainless steel containing molybdenum can also be suitable for high temperatures and dilute acetic acid vapors. For demanding requirements such as high temperature and high concentration acetic acid or containing other corrosive media, high alloy stainless steel valves or fluoroplastic valves can be selected.