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Pitting corrosion Austenitic staiidess steels owe their corrosion resistance to the formation, from the chrome (Cr) content of the steel, of a passive layer of chromium oxide on the exposed surface. Pitting occurs when the protective oxide film breaks down in small, isolated spots. The rate of attack tends to increase because of the differences in electric potential between the large surrounding passive surface and the active pit. This action is accentuated by the presence of saline solutions. A smooth surface, free of sensitive local minute pits or small depressions, reduces the potential for pitting to commence. The most appropriate quality of stainless for such duties should be selected. 

Klaproth analysed datolith, gypsum, and barytes. He missed the fluorine content of apatite, which was detected by Pelletier, but he detected sodium in cryolite and the fluorine content of teeth and fossil ivory, confirmed by Berzelius. He showed that native iron is free from nickel, which is contained in meteoric iron, and analysed chrome ironstone. He described the manufacture of alum at Tolfa. He confirmed (1801) an observation of Kennedy of Edinburgh (1797) that basalt contains soda, and discovered potash (previously regarded as confined to the vegetable kii dom) in the mineral leucite (1797). He made many analyses of ancient metal objects and glazes. ... 

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