“In 1836, Sorel in France took out the first of numerous patents for a process of coating steel by dipping it in molten zinc after first cleaning it. He provided the process with its name ‘galvanizing’."
The history of galvanizing starts over 300 years ago, when an alchemist-come-chemist dreamt up a reason to immerse clean iron into molten zinc and to his amazement, a shimmering silver coating developed onto the iron. This was to become the first step in the genesis of the galvanizing process.
Luigi GALVANE
Alessandro VOLTA
The story of zinc is closely interlinked with that of the history of galvanizing; ornaments made from alloys that contain 80% zinc have been found dating as far back as 2,500 years. Brass, an alloy of copper and zinc, has been traced to at least the 10th century BC, with Judean brass found in this period containing 23% zinc.
The famous Indian medical text, Charaka Samhita, written around 500 BC, mentions a metal which when oxidised produced pushpanjan, also known as ‘philosopher’s wool’, thought to be zinc oxide. The text details its use as an ointment for eyes and a treatment for open wounds. Zinc oxide is used to this day, for skin conditions, in calamine creams and antiseptic ointments. From India, zinc manufacture moved to China in the 17th century and 1743 saw the first European zinc smelter being established in Bristol.
Galvanizing HistoryIn 1780, an Italian, Luigi Galvani, discovered the electrical phenomenon of the twitching of a frog’s leg muscles when contacted by two dissimilar metals, namely copper and iron. Galvani incorrectly concluded that the source of the electricity was in the frog’s leg. The term ‘galvanization’ began to appear in the lexicon, connected partly to the work carried out by Michael Faraday.
Experiments with dissimilar metals were further pursued by Alessandro Volta, who came to believe that the flow of electrical current was caused by the contact of the dissimilar metals themselves. In 1800, Volta was able to prove this by constructing a stack of alternating zinc and silver plates with a piece of cloth soaked in a salt solution between the individual plates. This device, known as Voltaic pile, was the world’s first battery.
In 1824, Sir Humphrey Davy showed that when two dissimilar metals were connected electrically and immersed in water, the corrosion of one was accelerated while the other received a degree of protection.
Michael FARADAY
From this work he suggested that the copper bottoms of wooden naval ships (the earliest example of practical cathodic protection) could be protected by attaching iron or zinc plates to them. When wooden hulls were superseded by iron and steel, zinc anodes were still used.
In 1829 Henry Palmer of the London Dock Company was granted a patent for ‘indented or corrugated metallic sheets’, his discovery would have a dramatic impact on industrial design and galvanizing.
‘Galvanization’ was a term used during the 19th century to describe the administration of electric shocks.
In 1836, Sorel in France took out the first of numerous patents for a process of coating steel by dipping it in molten zinc after first cleaning it. He provided the process with its name ‘galvanizing’. It is interesting to note that Sorel was aware of the electrochemical nature of corrosion and the sacrificial role of the zinc coating on the iron. Originally, the word galvanizing did not refer to the process of coating but to the fundamental property offered by this coating.
In addition to Sorel’s patent of 1836, A British patent for a similar process was granted in 1837 to William Crawford.
Galvanized steel is all around us and plays a vital role in our everyday lives. It is used in construction, transport, agriculture, power transmission and everywhere that good corrosion protection and long life are essential. It, for instance, helps light our roads (lighting columns) and provide power for our homes, hospitals and offices (high voltage pylons) There are many other important industries that make use of galvanizing.
