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In metallurgy, non-ferrous metals are metals or alloys that do not contain iron (allotropes of iron, ferrite, and so on) in appreciable amounts.. Generally more costly than ferrous metals, non-ferrous metals are used because of desirable properties such as low weight (e.g. aluminium), higher conductivity (e.g. copper), [1] non-magnetic properties or resistance to corrosion (e.g. zinc). [2]
Noble metals tend to be resistant to oxidation and other forms of corrosion, and this corrosion resistance is often considered to be a defining characteristic. Some exceptions are described below. Copper is dissolved by nitric acid and aqueous potassium cyanide .
Refractory metals have high melting points, with tungsten and rhenium the highest of all elements, and the other's melting points only exceeded by osmium and iridium, and the sublimation of carbon. These high melting points define most of their applications. All the metals are body-centered cubic except rhenium which is hexagonal close-packed.
Bluing only works on ferrous materials, such as steel or cast iron, for protecting against corrosion because it changes iron into Fe 3 O 4. As aluminium and polymers do not rust, they cannot be blued, and no corrosion protection is provided. However, the chemicals from the bluing process can cause uneven staining on aluminium and polymer parts.
The corrosion resistance of the alloys may degrade significantly when some impurities (e.g. more than 40 ppm of carbon or more than 300 ppm of nitrogen) are present. [13] Corrosion resistance of zirconium alloys is enhanced by intentional development of thicker passivation layer of black lustrous zirconium oxide. Nitride coatings might also be ...
The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. It is not yet clear how exactly the patina formation differs from usual rusting, but it's established that drying of the wetted surface is necessary and that copper is the most important alloying element.
Fusible alloys are typically made from low melting metals. There are 14 low melting metallic elements that are stable for practical handling. These are in 2 distinct groups: The 5 alkali metals have 1 s electron and melt between +181 (Li) and +28 (Cs) Celsius; The 9 poor metals have 10 d electrons and from none (Zn, Cd, Hg) to three (Bi) p electrons, they melt between -38 (Hg) and +419 (Zn ...
These tanks contain, in order, alkaline detergent, water, sodium hydroxide at 140.5 °C (284.9 °F) (the blackening compound), and finally the sealant, which is usually oil. The NaOH (caustic soda) and elevated temperature cause Fe 3 O 4 (black oxide) to form on the surface of the metal instead of Fe 2 O 3 (red oxide; rust). While it is ...