Listed here for austenitic stainless steel, some brands at the beginning of the development is designed to a special corrosion-resistant purpose, but is not the same as in other corrosive environment cannot choose, some brand, although not formally named as a specialized brand I, but it does to be unique in some, and some medium corrosion resistant properties, and in other media does not necessarily apply.

Carbon dioxide stripping process is widely used to produce urea (a kind of efficient chemical fertilizer) at home and abroad. It is generally synthesized from carbon dioxide and ammonia under high pressure (140~250atm,1atm=101325Pa) and temperature 180~210℃. Under high temperature and high pressure, the intermediate reactant in the process of urea production - ammonium carbamate (ammonium urea solution), etc., has a strong corrosive to stainless steel - destroy stainless steel passivation film and depassivation effect. Under the condition of hypoxia, the corrosion rate of 00Cr17Ni14Mo2 (316L) is as high as 50mm/a, but if oxygen is added to urea, the stainless steel can be passivated, so that the application of 00Cr17Ni14Mo2 stainless steel in urea production plant becomes possible. However, it is found that the corrosion resistance of ordinary 00Cr17Ni14Mo2 is not enough after use. Subsequently, we developed a urea grade stainless steel (316UG) specially used for urea production.

316UG requires that the amount of chromium in steel should be ≥18%. Due to the harmful effect of C, S, P and other elements and residual δ-ferrite, the content of C should be ≤0.02%, the content of P and S should be ≤0.015%, and the content of δ-ferrite should be ≤0.6%. In order to ensure that δ-ferrite ≤0.6%, the amount of nickel in the steel should be in the medium and upper limit, 316UG has been widely used in the synthesis tower of carbon dioxide stripping urea production of four high pressure equipment tower and components.

00Cr25Ni22Mo2N (2RE69) is currently due to 316UG is the best one of the high temperature, high pressure urea corrosion resistance of a high grade stainless steel. Since the corrosion resistance of 316UG is still insufficient after long-term use, the application range of 00CrNi22Mo2N is expanding.

In the urea synthesizer and stripper, the corrosion resistance of 00Cr25Ni22Mo2N is the best. The corrosion resistance of Ni-free Cr-Mn stainless steel 0Cr17Mn14Mo2N (A4) is the worst. (From Introduction to Stainless Steel)
Table 2. Corrosion resistance of urea grade 00Cr17Ni14Mo2 and 00Cr25Ni22Mo2N in domestic urea medium