The Discovery of Chrome
In 1762, J. G. Legmann described an orange-yellow mineral discovered in Siberia’s Ural Mountains, which he called crocoite because it resembled the colour of egg yoke (krokos in Greek). Thirty-five years later, French chemist Nicolas-Louis Vauquelin identified a new metallic element in this mineral. He called it “chromium”, after the Greek khrōma, meaning colour, because of its colourful compounds. Indeed, the yellow deposit obtained by crushing the mineral was already being used as a paint pigment. After further research, Vauquelin found that trace elements of chrome give rubies their characteristic red colour and emeralds, serpentine and chrome mica their distinctive green.
A multiplicity of Uses
Chrome’s versatility soon became even more evident. While paint remained the main application for many years, in the 19th century potassium dichromate was found to be an excellent mordant in textile dyeing. A mordant (from the Latin mordere, to bite) helps dyes attach and adhere to fabric. A few years later, chromic sulphate was introduced in a process for tanning leather. A related application – chrome’s use as a timber preservative – dates from the early 20th century.
The 1850s saw the discovery of chromium plating – an electrodeposition that gives metal certain properties, including abrasion and wear resistance, corrosion protection, lubricity and aesthetic qualities.
Quite late in the 19th century, chrome began to be used in refractory bricks (an application which saw substantial growth in the 1930s). Its use in foundry sands, for moulding, did not come until the 20th century.
Chrome finds its true vocation
The first patent for the use of chrome in steel was granted in 1865. However, the large-scale use of chrome in metals had to await the development of the electric arc furnace in the early 1900s, which made it possible to smelt chromite into ferrochrome. At this stage, chrome was used to produce chrome metal – an alloy composed almost entirely of chrome.
Then stainless steel was discovered and the rest, as they say, is history. At the start of the 20th century, world production of chromite was less than 100,000 tonnes. In 2000 it was 16 million tonnes. In 2010 it had risen to 25 million tonnes.
“CHROME YELLOW” BUSES
In 1939, in North America, a yellow paint colour was adopted as the nationwide colour for school buses.
Against this colour, the buses’ black lettering would be easy to see in the semi-darkness of early morning. For years, the pigment used was chrome yellow, so the colour was originally called National School Bus Chrome.