Blackening


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Blackening

 

a type of oxide coating for iron and steel products, used for corrosion protection and for decorative purposes. The most common method of blackening is to immerse the products in a concentrated alkaline solution containing sodium nitrate or sodium nitrite as an oxidizer. As the concentration of the alkali is increased (other conditions being equal), the thickness of the oxide film also increases. A thin coating (20 to 40 angstroms) does not alter the external appearance of the surface nor does it provide practical protection for the metal against corrosion. Thick coatings (2.5 micrometers), which are black or grayish black, have poor mechanical strength. The best thickness is 0.6 to 0.8 micrometer. Blackening is a special case of blueing.

References in periodicals archive ?
However, the blackening has been largely ignored, save for recent articles by McEntire (2007), and Young (2016a, 2016b).
And what Machine Head is about on "The Blackening" is unfiltered rage.
Command considered adding its own in-house black-oxide finishing system in the past, but a growing preference for shiny shank toolholders and other factors caused a drop in blackening needs until a few years ago.
(7) Infections that can cause blackening of the esophageal mucosa include Canadida (8) and herpes (9) infections.
"It's really, really, bad luck not to have a blackening before you get married", says Lindsey
PX-5-L single-component blackening agent for stainless steels -- including martensitic, ferritic, austenitic and Duplex -- also works with cast and malleable irons.
Yesterday, flames 60 feet high raced towards Sydney, blackening bushland and coming close to suburbs within a mile of the city's central area.
For example, during the 1970s, a typical announcement in the New York Amsterdam News read: "Sunday Blackening: Variety of artists and speakers every Sunday.
HPM Corp, Mt Gilead, OH, a manufacturer of injection molding presses, recently installed a blackening system to replace paint for finishing large hydraulic manifolds and other machined components used in its presses.
That's why blackening the exterior of a rare steak with a flash searing leaves meat relatively free of HCAs, as does precooking it at relatively low temperatures in the microwave and then browning the surface quickly in a broiler.
There is no reason to doubt that the blackening of the notation in these instances conveyed precisely the meaning that blackened notation had always conveyed.