Cathodic protection is an electrical method of preventing corrosion on metallic structures situated in electrolytes. In practical applications, the structures most commonly provided with protection are constructed of iron or steel (including stainless steel) and the electrolytes are most often soil and water. Other metals commonly provided with cathodic protection include, lead sheathed cables, copper and aluminum piping, galvanized steel, and cast iron.
Cathodic protection has also been used successfully in unusual electrolytes such as concrete, calcium chloride and caustic soda. However, the vast majority of cathodic protection systems are used to prevent corrosion on steel structures in soil and water. Cathodic protection has become a standard procedure for many structures such as underground storage tanks, pipelines, water storage tanks, ship hulls and interiors, lock gates and dams, water treatment facilities, well casings, trash racks and screens, bridge decks, and steel pilings.
As far back as the Bronze Age, it was observed that metals were not very stable when subjected to their natural environments such as soil and sea water. About 1780, a physiologist, Luigi Galvani, reported on his experiments with metallic arcs of dissimilar metals. He was studying the muscular structure of the frog. He noticed that when the frogs were suspended on an iron rack by copper hooks, there was a twitching in their leg muscles. One of the foremost physicists of the period, Alessandro Volta, was able to demonstrate that the phenomenon was caused by electricity produced by the dissimilarity of the metals in contact with the biological specimens.
In 1824, Sir Humphry Davy, on contract to the royal Navy, discovered the principle of cathodic protection for the mitigation of natural corrosion processes. He was searching for a method to prevent corrosion of the copper-clad wooden hulls of English ships. He attached billets of zinc to the copper and observed that the zinc would corrode to save the copper. Today, over one and one-half centuries later, corrosion engineers are still using this same method of preventing corrosion damage by applying this same zinc anode cathodic protection to steel ships around the world.
Cathodic protection has also been used successfully in unusual electrolytes such as concrete, calcium chloride and caustic soda. However, the vast majority of cathodic protection systems are used to prevent corrosion on steel structures in soil and water. Cathodic protection has become a standard procedure for many structures such as underground storage tanks, pipelines, water storage tanks, ship hulls and interiors, lock gates and dams, water treatment facilities, well casings, trash racks and screens, bridge decks, and steel pilings.
As far back as the Bronze Age, it was observed that metals were not very stable when subjected to their natural environments such as soil and sea water. About 1780, a physiologist, Luigi Galvani, reported on his experiments with metallic arcs of dissimilar metals. He was studying the muscular structure of the frog. He noticed that when the frogs were suspended on an iron rack by copper hooks, there was a twitching in their leg muscles. One of the foremost physicists of the period, Alessandro Volta, was able to demonstrate that the phenomenon was caused by electricity produced by the dissimilarity of the metals in contact with the biological specimens.
In 1824, Sir Humphry Davy, on contract to the royal Navy, discovered the principle of cathodic protection for the mitigation of natural corrosion processes. He was searching for a method to prevent corrosion of the copper-clad wooden hulls of English ships. He attached billets of zinc to the copper and observed that the zinc would corrode to save the copper. Today, over one and one-half centuries later, corrosion engineers are still using this same method of preventing corrosion damage by applying this same zinc anode cathodic protection to steel ships around the world.
Source:www.bushman.cc/pdf/corrosion_theory.pdf
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