Chromium… the element that makes Harley Davidson’s Stainless Steel shine

Chromium… the element that makes Harley Davidson’s Stainless Steel shine

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Stainless steel, like plastic, is a material that we take for granted today, yet a century ago it was virtually unknown, and it was generally accepted that all steels must either be surrounded by some other protective material, or left to inevitable corrosion. The advent of rust-free steel is down to a magic ingredient in its chemistry - chromium. This metal, element number 24 of the periodic table, had been known since the late 1790s, when it was first identified by the French chemist, Louis Nicolas Vauquelin. But its early uses were far removed from the silvery sheen of Art Deco architecture. Indeed, Vauquelin named this new metal after the Greek word for colour, chromos - because chromium is associated with an extraordinary array of colours.

The ore from which Vauquelin isolated his first shiny nuggets of pure metal was discovered in Siberia. Called crocoite, it resembled bright orange-red needles.The mineral consisted of lead oxide and lead chromate, and the colour it produced became known to artists as "chrome red". In fact it provided a range of colours. Increase the lead oxide, and the hue became a heavier red. Strip out the lead oxide altogether, and you were left with the brilliant yellow of pure lead chromate. This "chrome yellow" would provide the iconic colour of the Swiss and German postal services, and US school buses. And also yellow lines on roads - as lead compounds are insoluble in water, they would not wash away in the rain.

A third pigment was provided by chromium oxide - "chrome green". Chromium's journey from the artist's palette to the architect's drawing board is itself colourful and contentious, and takes us to Sheffield, the world's first steel town.

In the mid-1920s that the classic stainless steel recipe was settled on - 18% chromium, plus the addition of 8% nickel, yielding a material that was far easier to cut.From there, it was a short leap to the clean lines and polished surfaces of the Harley Davidson motorcycle.

Today, stainless steels are used not only for their good looks, but also to build structures that can withstand some pretty corrosive environments - from orange juice vats to subsea pipelines, and Harley exhausts. "The steel is protected by a surface layer of chromium oxide, one of the hardest materials known," explains chemistry Prof Andrea Sella of University College London. "And so that means the metal is completely encapsulated. That's why the steel resists further corrosion and retains its shine."

Chromium can just as easily be used to plate steel as to mix into it. Take a bit of steel, place it in a bath of acid containing dissolved chromium, and then pass an electric current through it, and the chromium will naturally stick to the surface of the metal as it discharges electricity.

This was how another great icon was born - the engine of the Harley Davidson motorcycle.

In the 1953 film, The Wild One, Marlon Brando rode a Triumph, rather than a Harley, but it too glistened with stainless steel. And Brando wore leather - lots of it - which also would not have been the same without chromium.

We think even Harley Davidson would be impressed with the shine on our Stainleel Steel Worktops!

Source:
BBC