Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged in a bath of molten zinc
Named via French from the name of Italian scientist Luigi Galvani, the earliest use of the term was, in early 19th-century scientific research and medical practice, stimulation of a muscle by the application of an electric current. The term “galvanized” continues to be used metaphorically of any stimulus which results in activity by a person or group of people
Galvanizing protects the underlying iron or steel in the following main ways:
The zinc coating, when intact, prevents corrosive substances from reaching the underlying steel or iron.
The zinc protects iron by corroding first. For better results, application of chromates over zinc is also seen as an industrial trend
In the event the underlying metal becomes exposed, protection can continue as long as there is zinc close enough to be electrically coupled. After all of the zinc in the immediate area is consumed, localized corrosion of the base metal can occur
Although galvanizing will inhibit attack of the underlying steel, rusting will be inevitable after some decades of exposure to weather, especially if exposed to acidic conditions. For example, corrugated iron sheet roofing will start to degrade within a few years despite the protective action of the zinc coating. Marine and salty environments also lower the lifetime of galvanized iron because the high electrical conductivity of sea water increases the rate of corrosion, primarily through converting the solid zinc to soluble zinc chloride which simply washes away. Galvanized car frames exemplify this; they corrode much faster in cold environments due to road salt, though they will last longer than unprotected steel and even some low grade stainless steel