For a medium containing 30% sodium hydroxide at a temperature of 110°C, what is the best material for the equipment?
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For a medium containing 30% sodium hydroxide at a temperature of 110°C, what is the best material for the equipment?
It is better to line it with Q235B instead of 304
304 stainless steel is commonly used
Carbon steel and low-alloy steel should also work, but post-weld heat treatment is necessary. In accordance with the capacity regulations.
According to clause 6.7.1 of HG20581-1998, carbon steel and low-alloy steel cannot be used; it is recommended to use 304SS.
Based on corrosion data and corrosion manuals, chromium 13 stainless steel and chromium 17 stainless steel can be used, whereas chromium 18 nickel 9 stainless steel cannot. For carbon steel and low-alloy steel welded chemical containers that are not subjected to stress-relief heat treatment after welding or cold working, the operating temperature in a 30% sodium hydroxide solution must not exceed 54°C.
NaOH solutions with a concentration of over 10% can cause alkaline embrittlement in carbon steel, low-alloy steel, and stainless steel. The three necessary conditions for alkaline embrittlement are concentration, tensile stress, and temperature; carbon steel and low-alloy steel cannot be used at 110 degrees Celsius. It is recommended to use a stainless steel lining.
Please take a close look; it states that the upper temperature limit for cold working or when no post-weld heat treatment is applied is 54 degrees, and this limit can be applied after performing post-weld heat treatment. The tolerance specifications state the same thing.
This post was last edited by silicasliu on 2009-10-13 09:53 with EN 13445-2 material
In my opinion, carbon steel and low-alloy steel require heat treatment, as specified by the standards； But it's still better to use a stainless steel lining.
Practice has shown that neither carbon steel nor 304 works; heat exchangers made of carbon steel lasted only about a week, those made of 304 lasted a month, while those made of 316L lasted much longer. I’m not sure about the investment status; during the training, the instructor suggested using nickel or nickel alloys