Corrosion has always been one of the most challenging issues in chemical pump equipment. A small mistake can lead to severe damage, accidents, and even disasters. According to statistics, around 60% of the damage to chemical pumps is caused by corrosion. Therefore, when selecting a chemical pump, it is crucial to ensure that the material selection is scientifically sound.
A common misconception is that stainless steel is a "universal material" that can be used for any medium and environmental condition. This assumption is extremely dangerous. Here are some key considerations for selecting materials for different chemical media:
1. **Sulfuric Acid**: As a highly corrosive substance, sulfuric acid behaves differently depending on its concentration and temperature. For concentrated sulfuric acid (above 80%) at temperatures below 80°C, carbon steel or cast iron may offer good resistance. However, they are not suitable for high-speed flow or pump valves. Ordinary stainless steels like 304 and 316 have limited use in such environments. High-silicon cast iron or high-alloy stainless steels (like 20 alloy) are often preferred. Fluoroplastics, such as F46-lined pumps, are also cost-effective options. Our company offers fluoroplastic centrifugal pumps, FP FS series corrosion-resistant pumps, and CQB-F type magnetic drive pumps.
2. **Hydrochloric Acid**: Most metals, including various stainless steels, are not resistant to hydrochloric acid. Molybdenum high-silicon iron can be used only in low concentrations (up to 30%) and temperatures below 50°C. Non-metallic materials like rubber and plastics (e.g., polypropylene, fluoroplastics) are more suitable for transporting hydrochloric acid.
3. **Nitric Acid**: Most metals are corroded by nitric acid. Stainless steel is the most widely used material for nitric acid resistance. At normal temperatures, it performs well across all concentrations. However, molybdenum-containing stainless steels (like 316, 316L) may not always outperform ordinary stainless steels. For high-temperature applications, titanium or titanium alloys are typically used.
4. **Acetic Acid**: One of the most corrosive organic acids, acetic acid can severely corrode ordinary steel. Stainless steel, especially 316 with molybdenum, is an excellent choice. It can also handle high-temperature dilute acetic acid vapor. For high-temperature and high-concentration conditions, high-alloy stainless steel or fluoroplastic pumps are recommended.
5. **Alkali (Sodium Hydroxide)**: Steel is commonly used for sodium hydroxide solutions below 30°C and 30% concentration. Some factories still use ordinary steel at lower temperatures, though corrosion increases. Stainless steel doesn’t offer significant advantages over cast iron in terms of alkali resistance. If trace amounts of iron are acceptable, stainless steel is not recommended. For high-temperature lye, titanium or high-alloy stainless steel is preferred.
6. **Ammonia (Ammonium Hydroxide)**: Most metals and non-metals show slight corrosion in liquid ammonia or ammonium hydroxide. Copper and copper alloys should be avoided. Most materials are suitable for transporting ammonia.
7. **Salt Water (Seawater)**: Ordinary steel shows moderate corrosion in saltwater and sodium chloride solutions. Painting is often used for protection. Stainless steels generally have low uniform corrosion rates but may suffer from localized corrosion due to chloride ions. Our pumps are commonly made from 316 stainless steel.
This article is sourced from http://NewsDetail250T1.html, China Hardware Business Network. http://news.chinawj.com.cn. Editor: (China Hardware Business Network Information Center) http://news.chinawj.com.cn.Hotop mainly provide high quality tabletop solutions with full range of commercial flatware, glassware, chinaware, ideal for restaurant, hotel all day dining buffet,etc.
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