Editing Group 6 element (section)

===Historical development and uses===
During the 1800s, chromium was primarily used as a component of paints and in [[Tanning (leather)|tanning]] salts. At first, crocoite from [[Russia]] was the main source, but in 1827, a larger chromite deposit was discovered near [[Baltimore]], [[United States]]. This made the United States the largest producer of chromium products until 1848 when large deposits of chromite where found near [[Bursa]], [[Turkey]].<ref name="NRC">{{cite book|title = Chromium|author = National Research Council (U.S.). Committee on Biologic Effects of Atmospheric Pollutants|publisher = National Academy of Sciences|year = 1974 |isbn = 978-0-309-02217-0 |url = https://books.google.com/books?id=ZZsrAAAAYAAJ|page = 155}}</ref> Chromium was used for electroplating as early as 1848, but this use only became widespread with the development of an improved process in 1924.<ref name="Crplating">{{cite book|title = Nickel and Chromium Plating| publisher = Woodhead Publishing|year = 1993| isbn = 978-1-85573-081-6| pages = 9–12|chapter = History of Chromium Plating|author1=Dennis, J. K. |author2=Such, T. E. }}</ref>

For about a century after its isolation, molybdenum had no industrial use, owing to its relative scarcity, difficulty extracting the pure metal, and the immaturity of the metallurgical subfield.<ref name="Hoyt1921">{{cite book | last1 = Hoyt | first1 = Samuel Leslie | title = Metallography, Volume 2 | publisher = McGraw-Hill | year = 1921 }}</ref><ref name="Krupp1888">{{cite book | last1 = Krupp | first1 = Alfred | last2 = Wildberger | first2 = Andreas | title = The metallic alloys: A practical guide for the manufacture of all kinds of alloys, amalgams, and solders, used by metal-workers ... with an appendix on the coloring of alloys | publisher = H.C. Baird & Co. | year = 1888 | page = 60 }}</ref><ref name='Gupta1992'>{{cite book | last1 = Gupta | first1 = C.K. | title = Extractive Metallurgy of Molybdenum | publisher = CRC Press | year = 1992 | isbn = 978-0-8493-4758-0}}</ref> Early molybdenum steel alloys showed great promise in their increased hardness, but efforts were hampered by inconsistent results and a tendency toward brittleness and recrystallization. In 1906, [[William D. Coolidge]] filed a patent for rendering molybdenum [[Ductility|ductile]], leading to its use as a heating element for high-temperature furnaces and as a support for tungsten-filament light bulbs; oxide formation and degradation require that moly be physically sealed or held in an inert gas. In 1913, [[Frank E. Elmore]] developed a [[froth flotation|flotation process]] to recover [[molybdenite]] from ores; flotation remains the primary isolation process. During the [[World War I|first World War]], demand for molybdenum spiked; it was used both in [[Vehicle armor|armor plating]] and as a substitute for tungsten in [[high-speed steel]]s. Some British tanks were protected by 75&nbsp;mm (3&nbsp;in) [[mangalloy|manganese steel]] plating, but this proved to be ineffective. The manganese steel plates were replaced with 25&nbsp;mm (1&nbsp;in) molybdenum-steel plating allowing for higher speed, greater maneuverability, and better protection.<ref name="nbb" /> After the war, demand plummeted until metallurgical advances allowed extensive development of peacetime applications. In [[World War II]], molybdenum again saw strategic importance as a substitute for tungsten in steel alloys.<ref name="Millholland1941">{{cite news | first = Ray | last = Millholland | title = Battle of the Billions: American industry mobilizes machines, materials, and men for a job as big as digging 40 Panama Canals in one year | date = August 1941 | work = Popular Science | page = 61 }}</ref>

In [[World War II]], tungsten played a significant role in background political dealings. [[Portugal]], as the main European source of the element, was put under pressure from both sides, because of its deposits of [[wolframite]] ore at [[Panasqueira]]. Tungsten's resistance to high temperatures and its strengthening of alloys made it an important raw material for the arms industry.<ref name="portugal">{{cite journal|last=Stevens|first=Donald G.|year=1999|title=World War II Economic Warfare: The United States, Britain, and Portuguese Wolfram|journal=The Historian|volume=61|issue=3|pages=539–556|doi=10.1111/j.1540-6563.1999.tb01036.x}}</ref>