hypatia said:
What a fantastic bridge matt! Its just beautiful.
I think it was around the turn of the century when someone added chromium to steel and made the first stainless steel.
roughly around the turn-----the date several sites give is 1912
Astronuc has a link to a history of stainless, but this is also informative:
http://www.stainless-steel-world.net/basicfacts/history.asp
and especially this:
http://www.stainless-steel-world.net/basicfacts/history_first.asp
Wiki gives some 19th century forerunners of the 1912-1913 discovery
http://en.wikipedia.org/wiki/Stainless_steel
---quote Wiki---
The corrosion resistance of iron-chromium alloys was first recognized in 1821 by the French metallurgist Pierre Berthier, who noted their resistance against attack by some acids and suggested their use in cutlery. However, the metallurgists of the 19th century were
unable to produce the combination of low carbon and high chromium found in most modern stainless steels, and the high-chromium alloys they could produce were too brittle to be of practical interest.
This situation changed in the late 1890s, when Hans Goldschmidt of Germany developed an aluminothermic (thermite) process for producing carbon-free chromium. In the years 1904-1911, several researchers, particularly Leon Guillet of France, prepared alloys that would today be considered stainless steel. In 1911, Philip Monnartz of Germany reported on the relationship between the chromium content and corrosion resistance of these alloys.
Harry Brearley of the Brown-Firth research laboratory in Sheffield, England is most commonly credited as the "inventor" of stainless steel. In 1913, while seeking an erosion-resistant alloy for gun barrels, he discovered and subsequently industrialized a martensitic stainless steel alloy. However, similar industrial developments were taking place contemporaneously at the Krupp Iron Works in Germany, where Eduard Maurer and Benno Strauss were developing an austenitic alloy (21% chromium, 7% nickel), and in the United States, where Christian Dantsizen and Frederick Becket were industrializing ferritic stainless.
---end quote---
so it seems something subtle was going on, already in 1821 people KNEW to mix chromium in with iron and had the idea of stainless steel, but all the chromium available had TOO MUCH CARBON IN IT.
they were apparently using carbon to reduce the chromium oxide and win the metal from the oxide, which left a residue of carbon.
the breakthrough was roundabout. first learn to win aluminum from ITS oxide by electrolysis, then make powder aluminum and mix THAT with chromium oxide
then apply heat in the absence of air, and the aluminum GOBBLES THE OXYGEN taking it away from the chromium and so you get the pure metal (without residue of carbon) (there would be aluminum oxide but it would slag off, i guess)
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I could be wrong about the history, I am just interpreting what I think Wiki is saying. If somebody knows different, please say. If this is right then the curious roundaboutness is that you couldn't get stainless steel until you first figured out how to produce aluminum from its oxide by electricity.