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Galvanized iron is iron coated with zinc to resist corrosion. It is used for roofing, building materials, wire mesh, pipes, and decorative outdoor products. The process of galvanizing iron has several methods. Galvanized iron is not completely resistant to corrosion but remains strong.
Galvanized iron is iron ore that has been refined, shaped, and coated with zinc plating. Zinc provides the galvanizing, as zinc resists the corrosion typical of ungalvanized cast iron. Galvanized iron is produced and used for a wide variety of purposes, but its primary use is for sheet metal roofing and other building materials, such as posts for metal framing, metal shingles, and fencing. Other uses include wire mesh, pipes, roof ornaments and other decorative outdoor architectural products, gutters, flashings, metal buckets and connectors, such as screws and nails. The material resists rust and is therefore a very common material for outdoor projects.
The term galvanized comes from Luigi Galvani, an 18th-century Italian physician and physicist who experimented with bioelectricity and electrochemistry. His experiments and his research, centered on chemical and electrical reactions, did not lead directly to galvanized iron, but gave impetus to research on chemical reactions between metals. Zinc-coated iron, it was later discovered, resists the oxidation that turns bare iron into a red powder within a few years. Galvanized iron revolutionized metalworking and spawned the modern galvanized iron industry.
Iron is galvanized by several processes. The most common is electrogalvanization, the process of immersing the stamped iron product in an electrolyte solution of zinc sulfate. Hot-dip galvanizing, another common process, is iron dipped in molten zinc or zinc alloys. In sherardization, the iron is placed in an airtight vault and heavily dusted with powdered zinc particles. The fourth process, less effective than the others, is to paint or spray molten zinc or zinc pigments onto the metal.
The types of galvanizing of iron differ in various uses. For example, sheet metal roofing that is exposed to the most aggressive outdoor elements throughout the year is usually hot-dipped or galvanised. The bottom cover is painted with zinc. Gutters and pipes can be painted or sprayed.
Galvanized iron is not completely resistant to corrosion. Products that are exposed to concrete, acid rain, tannic acids from some trees, and excessive moisture will rust over time. Abrasions or the rubbing and twisting of the iron can crack the zinc coating, allowing moisture to seep into the cracks and rusting the iron underneath. Despite its vulnerabilities, galvanized iron products are extremely strong and remain the only corrosion resistant metal products available.
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