Blackening

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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Non-locals do not get blackened unless they are marrying a local.
On the menu for the night was Blackened ahi tuna for starters; Filet Oscar style with crab cakes and sauce for mains; and a decadent Creme brulee for dessert.
Yoga guru Ramdev was on Saturday attacked by a man who threw black ink on his face at a Press conference he was addressing on his plans to campaign against black money in the coming assembly elections Ramdev's left eye was blackened.
Add jalapeno, blackened tomatoes, tinned tomatoes, chilli powder, cumin, garlic powder, coriander, bay leaves and 1 litre/13/4 pints of the chicken stock.
I use a Sharpie to blacken them and try it on the frame.
The Cadi Ha is the traditional Flintshire May-time dance where men or boys blacken their faces and wear white clothes to bring in the summer.
Billowing clouds of war machines and violent explosions greedily swallow the glittering Mediterranean sun and blacken the brilliant Beirut sky.
Some actors would blacken their faces with soot before staging scenes that celebrated their community.
"Then we blacken him which is when we cover him in black waste oil from our tractors, old milk, wheat ears to make it itchy and cover him in cow slurry."
Why are Jewish groups that attempt to inflict economic damage on Israelis through BDS and blacken Israel's image given a place in the Israel Day Parade?
I suppose you could blacken any kind offish you care to bring home, either from a fishing trip or the market, but you'll always get the best results from firm-fleshed types, rather than softies such as speckled trout or yellowtail, whose fillets are more likely to break up during the process.