In acidic conditions, thiosulfate causes rapid corrosion of metals; steel and stainless steel are particularly sensitive to pitting corrosion induced by thiosulfate. Addition of molybdenum to stainless steel is needed to improve its resistance to pitting (AISI 316L hMo). In alkaline aqueous conditions and medium temperature (60 °C), carbon steel and stainless steel (AISI 304L, 316L) are not attacked, even at high concentration of base (30%w KOH), thiosulfate (10%w) and in presence of fluoride ion (5%w KF).
The natural occurrence of the thiosulfate group is practically restricted to a very rare mineral sidpietersite, Pb4(S2O3)O2(OH)2,[3] as the presence of this anion in the mineral bazhenovite was recently disputed.[4]
Thiosulfate extensively forms complexes with transition metals hence a common use is dissolving silver halides in film photography developing.[5] Thiosulfate is also used to extract or leach gold (sodium thiosulfate) and silver from their ores as a less toxic alternative to cyanide.[6]
Nomenclature[edit]