Aluminium dross

Dross is a mass of solid impurities floating on a molten metal or dispersed in the metal, such as in wrought iron. It forms on the surface of low-melting-point metals such as tin, lead, zinc or aluminium or alloys by oxidation of the metal. For higher melting point metals and alloys such as steel and silver, oxidized impurities melt and float making them easy to pour off.

With wrought iron, hammering and later rolling remove some dross.[1] With tin and lead the dross can be removed by adding sodium hydroxide pellets, which dissolve the oxides and form a slag. If floating, dross can also be skimmed off.

Dross, as a solid, is distinguished from slag, which is a liquid. Dross product is not entirely waste material; for example, aluminium dross can be recycled and is also used in secondary steelmaking for slag deoxidation.[2]

Etymology and usage

The term dross derives from the Old English word dros, meaning the scum produced when smelting metals (extracting them from their ores). By the 15th century it had come to refer to rubbish in general.[3] Dregs,[3] and the geological term druse are also thought to be etymologically related.[4] Popular non-metalworking uses of the word are derogatory:

See also


  1. ^ Landes, David S. (1969). The Unbound Prometheus: Technological Change and Industrial Development in Western Europe from 1750 to the Present. Cambridge, New York: Press Syndicate of the University of Cambridge. p. 91. ISBN 0-521-09418-6.
  2. ^ Kogel, Jessica Elzea; Society for Mining, Metallurgy, and Exploration (2006), Industrial minerals & rocks: commodities, markets, and uses (7th ed.), SME, p. 1406, ISBN 978-0-87335-233-8.((citation)): CS1 maint: multiple names: authors list (link)
  3. ^ a b "Dross".
  4. ^ Chambers's Etymological Dictionary of the English Language. W & R Chambers. 1875. p. 142. ISBN 9781402168093.
  5. ^ "dross"