In order to prevent the thickness of container parts from thinning due to corrosion and mechanical wear, the corrosion allowance of cylinders, heads, nozzles, manholes and internal parts in contact with working medium should be considered. For corroded or worn parts, the corrosion allowance should be determined according to the expected container life and the corrosion rate of medium to metal materials.
The corrosion allowance can generally be determined according to the uniform corrosion rate of steel in the medium and the design life of the container. Generally, due to different service conditions, different materials and different structural characteristics, there are detailed design reference values, which can be found in relevant design manuals. Without special corrosion, for carbon steel and low alloy steel, the corrosion allowance shall not be less than1mm; For stainless steel, when the corrosion of medium is minimal, the corrosion allowance is zero.
However, corrosion allowance is only meaningful to prevent uniform corrosion damage; For non-uniform corrosion such as stress corrosion, hydrogen embrittlement and crevice corrosion, poor corrosion effect can be prevented by increasing corrosion allowance. At this time, the emphasis should be placed on selecting corrosion-resistant materials or carrying out appropriate anti-corrosion treatment.