| Updated February 25, 2016Have you ever wondered what the difference is between galvanized metal and tin? Galvanized metal is a form of steel that has a thin coating of zinc oxide. Acting as a barrier between steel and the atmosphere, zinc protects corrosive substances from reacting with metal, which can cause it to weaken over time. Zinc also acts as a “sacrificial anode”—meaning even if the zinc coating is damaged in some way, the remaining zinc will protect the metal. Tin, on the other hand, resists corrosion from water, but can be attacked by acids and alkalis.
Tin can’t be galvanized, but is sometimes alloyed with other metals to prevent corrosion. Tinplate is a process of coating a thin sheet of steel by dipping it in molten metal or by electrolyte deposition, to create a strong, formidable metal that is both noncorrosive and nontoxic. Common uses for tinplate include food and beverage containers, paint cans, magnet boards, and electronic parts.
Galvanized metal has many uses in industrial and architectural metal fabrication, especially for metal products designed for outdoor use or any product that will be exposed to corrosive effects. Galvanized steel is frequently used as a building material because it provides strong support that requires a lower foundation load, and galvanized metal roofing can withstand extreme weather. Common uses for galvanized metal include handrails, flashing and gutters, chain link fencing, nails, support beams, appliances, precision instruments, bike racks, playground equipment, road grates and in the familiar galvanized buckets. Galvanized metal is also frequently used in aircraft, automobile, and ship production.
Galvanization has actually been around for quite a while. Named for Italian scientist Luigi Galvani, and known as Faradism during the 19th century, a form of galvanization may have been used as early as the 4th century during the Iron Pillar construction in Delhi, India. Galvanized iron was also discovered on Indian armor during the 17th century, and “galvanic paint” was invented in France in 1837.
Today the most common methods for galvanizing metal are:
Electrogalvanizing by immersing iron or steel in an electrolyte solution of zinc sulfate. This deposits a coating of pure zinc on the metal’s surface.
Hot-dip galvanizing by immersing steel or iron into molten zinc.
Sherardizing is a method that surrounds the steel with metallic zinc dust in an air-free enclosure. This method is often used on architectural elements.
Metallic spraying applies a fine spray of molten zinc to steel or iron. When this method is used, it can be heated and fused to create an alloy.
Fun fact: The Tin Man in The Wizard of Oz probably contained other metals in addition to tin, as tin doesn’t rust.