Glvanisation or galvanization is the process of applying a protective zinc coating to iron or steel, to prevent corrosion and rusting. It is also called galvanizing.
Since the zinc acts as a sacrificial coating, it protects the steel or iron underneath and can therefore extend the lifespan of metal parts. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc.
But galvanization is a complex process that can be carried out in several ways. Different forms of galvanizing exist, including:
- Hot-dip galvanizing
- Electro Galvanizing
- Mechanical Coating
- Zinc Spraying (Metalizing)
- Zinc Dust painting.
How does galvanisation prevent rusting?
Galvanizing protects from rust in a number of ways:
- It forms a barrier that prevents corrosive substances from reaching the underlying steel or iron.
- The zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc.
- The zinc protects its base metal by corroding before iron.
- The zinc surface reacts with the atmosphere to form a compact, adherent patina that is insoluble in rainwater.
Which holes is required for galvanized steel and what is its purpose?
Vent holes are required for galvanization of steel members. The primary reason for vent and drain holes is to allow air to be evacuated from within and around the fabrication, allowing it to be completely immersed in the cleaning solutions and molten zinc and for the excess zinc and solutions to drain out and away from the part.
The secondary reason is that if fabrications to be galvanized are not properly vented, cleaning solutions or rinse waters trapped in overlapping or contacting surfaces flash to steam. The resulting pressure increase (up to 3600 psi [25MPa]) can rupture the fabrication. Additionally, trapped moisture that flashes to steam can result in localized uncoated surfaces.
Conclusion
Galvanized metal is more common than you might think. Structures like building frameworks, lintels, metal benches, balconies, ladders, and fire escapes can all be made from galvanized metal to ensure a longer lifespan and adequate protection from corrosion and damage.