Improved pre-treatment of porous stainless steel substrate for preparation of Pd-based composite membrane

• Published in: Canadian journal of chemical engineering 2013-10, Vol.91 (10), p.1695-1701
• Main Authors: Xu, Nong, Ryi, Shinkun, Li, Anwu, Grace, John R., Lim, Jim, Boyd, Tony
• Format: Article
• Language: English
• Subjects: alumina layer; Aluminum oxide; Coating; Hydrogen permeation; Membranes; Palladium; palladium (Pd) membrane; porous stainless steel; pre-treatment; Repair; Roasting; Stainless steels; surface profile
• ISSN: 0008-4034; 1939-019X
• DOI: 10.1002/cjce.21793

The integrity and robustness of Pd‐based composite membranes depend heavily on the quality of the metallic substrate. This paper presents an improved method for pre‐treating the substrate. Detailed pre‐treatment steps of these porous stainless steel substrates included washing, polishing, etching, coating the first alumina layer, calcining the first alumina layer, coating the second alumina layer, calcining the second alumina layer and repair. The repair cycle was the most helpful step, greatly improving the membrane reproducibility and stability. Repeat coating with dilute suspensions of alumina particles of 0.3 µm mean diameter can repair defects on the top alumina layer. The hydrogen permeation flux was 268 × 10−4 N m3/(m2 h Pa) after one repair cycle, decreasing by 14% after an additional repair cycle. The hydrogen permeation flux of the pre‐treated porous stainless steel substrate was thus maintained at a level comparable with previous work. Surface topography revealed that the average roughness was reduced from 1.15 to 0.47 µm, and the surface Maximum Peak to Valley decreased from 17.5 to 6.0 µm/mm2 as a result of the pre‐treatment.