How to choose a corrosion resistant valve?The media conveyed in various pipelines in the chemical industry are usually corrosive to a certain extent, such as sulfuric acid, hydrochloric acid, nitric acid and other corrosive media. All corrosion protection is the most basic requirement of chemical equipment. Of course, chemical valves are no exception, and the material selection of the valve must be anti-corrosion. If the chemical valve is selected incorrectly, it will damage the equipment in the slightest, and cause major accidents in severe cases, causing harm to machinery, equipment and even people. However, for different corrosive media, the selection of valves is also different. This article discusses the main points of valve material selection for some commonly used chemical media:Anti-corrosion valve selection.
How to choose a corrosion resistant valve?
Hydrochloric acid: Most metal materials, including various stainless steel materials, are not resistant to hydrochloric acid corrosion, and high-silicon-containing ferrosilicon can only be used for hydrochloric acid below 50°C and 30%. Contrary to metal materials, most non-metallic materials have good corrosion resistance to hydrochloric acid, so rubber-lined valves (such as fluoroplastics, etc.) are the best choice for transporting hydrochloric acid. However, if the temperature of the medium exceeds 150°C, or the pressure is greater than 16 kg, any plastic (including chlorine plastic or even polytetraoxyethylene) will be difficult to handle. For hydrochloric acid exceeding this condition, there is no such thing on the market. There are ideal valves.How to choose a corrosion resistant valve?
Sulfuric acid: As one of the strong corrosive media, sulfuric acid is an important industrial raw material with a wide range of uses. Sulfuric acid with different concentrations and temperatures has a large difference in the corrosion of materials. For concentrated sulfuric acid with a concentration of more than 80% and a temperature of less than 80°C, carbon steel and cast iron have better corrosion resistance, but it is not suitable for high-speed flowing sulfuric acid. , Not suitable for valve materials, ordinary stainless steel such as 304, 316 also has limited use for sulfuric acid medium. Therefore, pump valves for transporting sulfuric acid are usually made of high-silicon cast iron (difficult to cast and process), high-alloy stainless steel (No. 20 alloy valve), and fluoroplastics have good sulfuric acid resistance. s Choice. If the pressure is too high and the temperature rises, the use point of the plastic valve will be impacted, so you can only choose a ceramic ball valve that is much more expensive than it.Valve selection for strong acids and bases
Anti-corrosion valve selection
Nitric acid: Most of the general metals are rapidly corroded and destroyed in nitric acid. Stainless steel is the most widely used nitric acid-resistant material. It has good corrosion resistance to all concentrations of real acids at room temperature. It should be noted that copper-containing stainless steel (such as 316, 316L) has no better corrosion resistance to acid than ordinary stainless steel (such as 304, 321), sometimes even worse than
Valve selection for strong acids and bases
Acetic acid: Acetic acid is one of the most corrosive substances in organic acids. Ordinary steel will be severely corroded in acetic acid of all concentrations and temperatures. Stainless steel is an excellent material for acetic acid resistance. Aluminum-containing 316 stainless steel is also suitable for high temperature and dilute Acetic acid vapour. High-alloy stainless steel or fluoroplastic pumps can be selected for high-temperature, high-concentration acetic acid or other corrosive media.
Salt water/sea water: The corrosion rate of ordinary steel in chloroform, sea water, and salt water is not too high. Generally, coatings must be used to protect various types of stainless steel. The uniform corrosion rate is also very low, but localized corrosion may be caused by atmospheric ions, usually It is better to use aluminum bronze or 316 stainless steel.
How to choose a corrosion resistant valve? If you need anti-corrosion valves, you can take a look at our lined valve series, or contact us for selection