What is the impact of chloride ions on pipe selection?
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Dear experts: Do we need to consider anything special when choosing pipe materials in the presence of chloride ions in the liquid phase? Is corrosion only present when the chloride ion concentration reaches a certain level? What type of pipe should we choose when there is chloride corrosion? Are there any relevant standards for guidance? THANK YOU !
The liquid phase contains chloride ions; if these ions come from positive salts, electrochemical corrosion issues must be taken into consideration. If an acidic solution is formed, acid corrosion must also be addressed. Additionally, titanium can react with dry chlorine to form chlorides, which alters the properties of the metal and can lead to intergranular corrosion. When choosing a material for pipes, various factors need to be considered. The simplest approach is to seek advice from companies in the same industry.
Based on experience, chloride ions at 300 PPM cause corrosion in carbon steel pipes, while at 500 PPM they cause corrosion in stainless steel pipes.
If the temperature is low (below 300°C), non-metallic materials (ceramics, fiberglass reinforced plastic, etc.) are used； If the temperature is high, non-metallic materials (quartz glass or graphite) can be used, as well as alloy steel (nickel-molybdenum-chromium-iron alloy).
Pure Cl ions, in the form of a salt solution, I think should not cause much corrosion to carbon steel, but they do have an effect on stainless steel.
It is recommended to use plastic composite pipes with a steel framework, as they are resistant to pressure and corrosion; in particular, they can withstand chloride ion corrosion, and their overall cost is lower than that of stainless steel.
Application areas of Inconel 600: 1. Thermocouple sheaths in corrosive atmospheres. 2. Production of vinyl chloride monomer: resistance to chlorine, hydrogen chloride, oxidation, and carburization corrosion. 3. Oxidation of uranium to hexafluoride: resistance to hydrogen fluoride corrosion. 4. Production and use in environments involving corrosive alkali metals, especially those with sulfides present. 5. Production of titanium dioxide using chlorine. 6. Production of organic or inorganic chlorides and fluorides: resistance to chlorine and fluoride corrosion. 7. Nuclear reactors. 8. Retorts and components in heat treatment furnaces, particularly in carburizing and nitriding atmospheres. 9. Catalytic regenerators in petrochemical production; alloy 600 is recommended for use at temperatures above 700°C to achieve a longer service life. Hu Zhenfei, www.nmc-cn.com, www.NickelAlloy.com
This post was last edited by hatawoo on 2011-4-6 at 10:14. It still depends on the chloride content and temperature. Generally, austenitic stainless steel is not recommended, as chlorides cause severe corrosion of austenitic materials. For ordinary applications, carbon steel or carbon steel lined with PP can be used; of course, if you have the means, Monel alloy is an excellent choice:lol (Monel has outstanding resistance to chloride-induced stress corrosion cracking)