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Protecting steel. Many compounds have been investigated in the past for protecting ferrous metal, in petrochemical installations, from corrosive attack by chemical products and H2S. An experience of this type of corrosion was encountered with Lacq natural gas which contained approximately 15% H2S in addition to CO2, and porous kansite (Fe9S8) crystals were formed on the metal. A degree of protection can be obtained, it is claimed, by the presence of pyrite (FeS2) as well as pyrrhotite (Fe7S8), which can be produced from Kansite by reaction with iron pentacarbonyl in the vapour phase. This treatment is carried out in an inert atmosphere at 260°C. (927,260—Soc. Nationale des Petroles d'Aquitaine, France.)