Natural Occurrence, Minerals and Ores

Because nuclides of iron are especially stable with the highest binding energy per nucleon (e.g., -8.79 MeV/nucleon for Fe), its cosmic abundance is particularly high, and it is thought to be the main constituent of the Earth s inner core as an iron-nickel alloy (see Section 13.2), named for its chemical composition NiPe by the Austrian geophysicist Suess. The relative Earth s crust abundance is about 5.63 wt.% Fe hence it is the fourth most abundant element after oxygen, silicon, and aluminum and the second most abundant metal after aluminum. 

Nital is the most common etchant for steels. Do not store nital with more than 3 wt.% nitric acid in ethanol due to decomposition. Use by immersion or swabbing applying a low pressure. 

Picral is better than nital for revealing annealed microstructures. Does not reveal ferrite grain boundaries. Etch by immersion or swabbing. 

Vilella s reagent is good for higher alloyed steels, tool steels, and martensitic stainless steels. Etch by immersion or swabbing. 

Etch for duplex stainless steels. Immerse specimens 15-45 min to reveal the grain and phase boundaries in duplex stainless steels. 

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Natural occurrence, minerals, and ores. Boron is extracted from borate minercds such as borax or tincal, kernite, colemanite, and ulexite occurring in evaporitic brine deposits located in desert areas worldwide such as in the USA in Boron, CA and Turkey. 

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