![]() ![]() This is also used to protect the metal parts in water heaters. For example, the rusting of underground iron storage tanks and pipes can be prevented or greatly reduced by connecting them to a more active metal such as zinc or magnesium ( ). This is cathodic protection and can be used for metals other than just iron. This suggests that this approach should work with other active metals.Īnother important way to protect metal is to make it the cathode in a galvanic cell. Thus, even if the zinc coating is scratched, the zinc will still oxidize before the iron. Since zinc has a lower reduction potential, it is a more active metal. Zinc is more easily oxidized than iron because zinc has a lower reduction potential. Zinc-plated or galvanized iron uses a different strategy. The chromium tends to collect near the surface, where it forms an oxide layer that protects the iron. ![]() For example, stainless steel is mostly iron with a bit of chromium. ![]() Other strategies include alloying the iron with other metals. As long as the paint remains intact, the iron is protected from corrosion. The layer of paint prevents the water and oxygen necessary for rust formation from coming into contact with the iron. One way to keep iron from corroding is to keep it painted. The speed of the spontaneous reaction is increased in the presence of electrolytes, such as the sodium chloride used on roads to melt ice and snow or in salt water. Once the paint is scratched on a painted iron surface, corrosion occurs and rust begins to form. ![]()
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