Selection of corrosion margin for pressure vessels

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For a medium that is not specified in any pressure vessel standards, how should the corrosion allowance be determined? What is the relationship between it and the annual corrosion rate? It is stated on the internet that grade 1 corrosion corresponds to no corrosion at all, with a corrosion rate of <0.05 mm/year, and the corrosion allowance in this case is 0 mm； Grade 2 corrosion corresponds to mild corrosion, with a corrosion rate of 0.05–0.13 mm/year and a corrosion margin of ≥1 mm ； Grade 3 corrosion indicates the presence of corrosion; the corrosion rate is 0.13–0.25 mm/year, and the corrosion margin is ≥2 mm ； A corrosion level of grade 4 corresponds to severe corrosion, with a corrosion rate of >0.25 mm/year and a corrosion margin of ≥3 mm. Where can I find this information (technical documents or sources)? I would appreciate guidance from experts