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We explain what black oxide coating means and what the blackening process is used for. Learn about the thickness, conductivity and weldability. This process is also known as gun bluing, oxiding, blackening, black passivating and the list goes on...
Purpose - It is used to add mild corrosion resistance and for appearance and to minimize light reflection.
What is it? - Black Oxide or Blackening is actually a conversion coating without any significant dimensional changes to the part! That is the real beauty of this brilliant process. No other coating process produces properties and characteristics like this for less cost.
The Black Oxide finish is a result of the surface being converted (does not add to it) into Magnetite (Fe3O4). It is formed by a chemical reaction produced when the part's iron ferrous alloy surface is immersed in an alkaline aqueous salt solution bath.
It should be noted that it is possible to oxidize non-ferrous metals under suitable conditions to form black oxides.
The black oxide bath temperature in a "hot" oxide process is approximately operated at about 285'F, a "warm" oxide process operates at about 195'F and "cold" oxide process operates at room temperature. Each process has it's own unique advantages and application / appearance will dictate the process path.
What alloys will work with Black Oxide? - Black oxide finishing is for ferrous materials, stainless steel, copper, copper based alloys, zinc, powdered metals and silver solder.