Details

Autor(en) / Beteiligte

• Deakin, Jane
• Dong, Zehua
• Lynch, Benjamin
• Newman, Roger C

Titel

De-alloying of type 316 stainless steel in hot, concentrated sodium hydroxide solution

Ist Teil von

• Corrosion science, 2004-09, Vol.46 (9), p.2117-2133

Ort / Verlag

Oxford: Elsevier Ltd

Erscheinungsjahr

2004

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The formation of “nickel” layers on austenitic stainless steel in strong caustic solutions was reported in 1979. We now report a detailed study that clarifies the nature of this de-alloying process and establishes firm links with other metal-environment systems that show de-alloying and associated stress corrosion cracking. De-alloying of iron from 316SS in 50% NaOH at 140 °C proceeds only as far as a solid solution with a Ni/Fe atomic ratio of ca. 1.3 (56 at.% Ni if we neglect the other elements present). Chromium is mostly dissolved and/or reprecipitated during this process. X-ray diffraction shows that the residue is a solid solution of intermediate composition, not a mixture of pure Ni and stainless steel. The removal of only half the iron conveniently explains why the de-alloyed layer is a connected porous network. Electrode capacitance measurements and FEG-SEM examination show that the de-alloyed layer has extremely fine nanoporosity.