Galvanització

Galvanització (galvanization) is the process of applying a protective zinc coating to steel or iron to prevent corrosion. The most common method is hot-dip galvanizing, in which parts are cleaned and immersed in molten zinc at around 450°C, forming zinc-iron alloy layers bonded to the substrate and a zinc outer layer. Electrogalvanizing deposits zinc by electroplating, producing thinner coatings suitable for complex shapes, while sherardizing and mechanical plating use zinc powders.

The corrosion protection arises from sacrificial protection and barrier protection. Zinc is more electrochemically active than iron, so it preferentially corrodes, protecting the base metal even if the coating is damaged; the layer also acts as a physical barrier.

Thickness is specified as coating weight in g/m2 or, in some cases, micrometers. Hot-dip galvanizing typically yields thicker coatings than electrogalvanizing. Standards include ISO 1461 for hot-dip galvanized coatings on iron and steel structures.

Applications include structural steel in buildings and bridges, road and water infrastructure, pipelines, electrical towers, fencing, and automotive parts.

Advantages include long service life, good resistance to weathering, low maintenance, and high recyclability of zinc. Limitations involve reduced performance in highly aggressive environments, potential damage from abrasion or welding, and the need for re-galvanizing or repair if the coating is compromised. Surface preparation is important, with degreasing and rust removal prior to coating. Environmental considerations focus on managing zinc-containing wastes and effluents generated during production.