![]() ![]() The metal being protected serves as the cathode, and so does not oxidize (corrode). The more active metals (lower reduction potential) are called sacrificial anodes because as they get used up as they corrode (oxidize) at the anode. 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. See Monroe’s Screws.Once the paint is scratched on a painted iron surface, corrosion occurs and rust begins to form. And because the zinc covers the screw’s entire exterior, the actual metal from which the screw is made won’t be exposed to moisture or oxygen. Whether a screw is galvanized or zinc-plated, it will feature a zinc shell. Therefore, zinc serves as a protective barrier for screws. When compared to steel, for example, zinc corrodes about 30 times more slowly. How exactly does zinc protect screws from corrosion? Well, zinc can still corrode, but it corrodes at a significantly slower rate than other metals and alloys. When a screw is exposed to moisture and oxygen, it may undergo oxidation, thus corroding. Unfortunately, all of these metals and alloys are vulnerable to corrosion. Screws, of course, are typically made of metals and alloys, some of which include steel, aluminum and brass. Corrosion Protectionīoth galvanization and zinc-plating offer a high level of protection against corrosion. The electrical current causes the zinc ions to bond with the screw, resulting in the formation of a protective zinc shell similar to that created with galvanization. Next, an electrical current is applied to the solution. Basically, the screw is placed inside a container filled with water, saline and a zinc anode. ![]() Zinc-plating is a finishing process that relies on electricity to create a protective layer of zinc on the surface of a workpiece, or in this case, a screw. Instead of dipping the screws in molten zinc, though, it involves a completely different method. Like galvanized screws, zinc-plated screws feature a protective outer layer of zinc. As the screw cools, the molten zinc hardens, thereby forming a shell on the screw’s exterior. After soaking in the molten zinc for an adequate amount of time, the screw is removed and allowed to cool. When a screw is galvanized, it’s submerged inside a container filled with molten zinc. Known as hot-tip galvanizing, this finishing process adds a layer of zinc over the surface of a screw. Galvanized screws are characterized by the presence of a protective zinc shell that’s achieved by submerging the screws in molten zinc. While they both feature a protective zinc shell, though, they each involve a different method. Because of the similarities between them, many people assume that galvanized screws and zinc-plated screws are the same. Technically speaking, galvanized screws feature a protective zinc shell as well. Screws are often plated with zinc or galvanized to protect against corrosion. ![]()
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