Timakhala ngati zitsulo zazitali 20 ku Astm \ / a ASME \ / / DeD. Aloy 20, omwe amatchedwanso "wopala matabwa 20" ndi "20CB-3", ndi chromium-romium-molybdenum kapangidwe ka zitsulo zopangidwa ndi ma sulfuric acines a sulfuric a sulfuric acid. Kutsutsana kwawo kuvunda kumangothandizanso kugwiritsa ntchito zinthu zina zambiri mu mankhwala, chakudya, mafakitale a mankhwala opangidwa ndi plastrics. Chimodzi mwazifukwa zazikulu 20 zoyeserera 20 zili zofala kwambiri ndikuti amakana pheng ndi chloride ion kuturuka, ndipo zokhuza zawo zamkuwa zimaziteteza ku sulfuric acid.