SULFEX PROCESS:DEPASSIVATION OF STAINLESS STEEL

摘要

The time required to break the passivation of films on 30V stainless steel produced by 1 hr treatment in refluxing 15.8 M HN0^-0.025 M Cr(Ⅲ) decreased as the sulfuric acid concentration increased and increased greatly when nitric acid was added to the sulfuric acid. The films resisted refluxing 6 M H2SO4 for 7 min, 6 M H2SO4-0.00l M HNO3 for 2 hr, and 6,M H2SO4-0.0l M HNO3, for several days. In refluxing 12 M H2SO4 the films dissolved in about 10 sec with up to- 0.001 M HNO3 in the solution, but 0.5 hr was required with 0.01 M HNO3. The addition of .0.1 M HCOOH to refluxing sulfuric acid solution effectively destroyed as much as 0.01 M HNO3. Films on stainless steel specimens in contact with platinum resisted refluxing 6 M H2SO4 for several hours. Films on bundles of 30^ stainless steel tubes brazed together with Nicrobraze-50 dissolved instantly in refluxing 6 M H2SO4.