MATERIALS SELECTION FOR HBR SERVICE

This study was undertaken to determine the compatibility of hydrogen b romide (HBr) with common materials of construction used for specialty gas delivery systems. Reactions between reactive gases and materials o f construction can result in the formation of particles and volatile m etal complexes as well as the creation of corrosion products that can retain water. We found that when moisture is below 1 ppm, (designated as anhydrous), bromine From HBr is not incorporated beyond the native oxide of electropolished 316L stainless steel (EP316L) and no macrosco pic degradation of the metal occurs. Also, if adequate purging and eva cuation procedures are followed to remove the HBr, this material can b e exposed to moist air without diminishing the initial surface quality . However, if adequate precautions are not followed to eliminate water in the presence of HBr, iron-and bromine-rich crystalline deposits fo rm on the surface. Purge and evacuation procedures are inadequate for removal of the reactive species on this surface and corrosion proceeds upon subsequent exposure to air. EP316L exposed to HBr containing 170 0 ppm, H2O appears visually unaltered, but close inspection by SEM rev eals the onset of corrosion. Of the materials examined in this study, Nickel-200 and Hastelloy C-22 are more resistant to HBr corrosive envi ronments. In contrast, deleterious reactions occur between anhydrous H Br and elemental iron and the iron-rich surface of oxygen-passivated 3 16L.