Please, experts, help analyze the corrosion condition of the following equipment!
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Our company has an alkali washing tank that is not operating within the specified pressure range. The medium consists mainly of crude dichloroethane, with an alkali content of around 1-3%. The operating temperature is between 40-60 degrees Celsius, and the operating pressure is 0.3 kg/cm2g. The tank has only been in use for 7 months, yet the feed pipe suffers from severe corrosion; there are corrosion-induced leaks at the welds of the inlet cylinder, and the inner wall is covered with many corrosion pits. The material used for the tank is 16MnR. I would like to ask everyone why the corrosion is so severe. Thank you!
This device does not fall within the category of pressure vessels
In a wet hydrogen sulfide environment, medium-strength 16MnR spherical tank steel primarily develops hydrogen-induced cracks and hydrogen bubbling in the base metal, resulting in numerous delamination defects within the material
The original poster can take a look at this to see if it’s helpful to you! http://www.cspt.org.cn/manage/wenzhang/2006211.pdf
There is no H2S in the material; only a small amount of alkaline NaOH, with a concentration of 1-3%
The corrosion of equipment caused by alkalis is generally known as alkali embrittlement. It is related to the concentration of alkalis in the medium as well as the temperature, and it falls under the category of stress corrosion. Stress-relief heat treatment should be carried out during the manufacturing of the equipment, and materials with low tensile strength (such as 20R and Q235-B) should be used.