Period 6 element heavy metal, lead is a neurotoxin that accumulates both in soft tissues and the bones. Lead poisoning has been documented from ancient Rome, ancient Greece, and ancient China. Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent other metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when newly made, but often seen in air with a pink tinge owing to the surface
Dry lubricant room temperature to form a solid lubricant. Pastes are grease-like lubricants containing a high percentage of solid lubricants used for assembly and lubrication of highly loaded, slow-moving parts. Black pastes generally contain MoS. For high temperatures above 500 °C, pastes are composed on the basis of metal powders to protect metal parts from oxidation necessary to facilitate disassembly of threaded connections and other assemblies. Dry-powder tumbling is an effective application method. The bonding can be improved by prior phosphating of the substrate. Use of free powders has its limitations, since adhesion of the solid particles to the substrate is usually