Spin Galvanizing

Hot dip galvanizing process consists of three distinct phases:

• Pre-treatment.

• Galvanizing.

• Inspection.

Pre-treatment:

• Pre-treatment for galvanizing consists of four separate stages:

• Inspection: Items are inspected to ensure they are safe and suitable to galvanize. This involves checking whether they are adequately vented. Surfaces are checked for signs of contamination with paint, grease, etc. as these will not be removed in the process and would cause the process to fail.

• Degreasing: Steel is immersed in a degreasing solution which removes light oil contamination.

• Pickling: Acid strips the steel surface back to clean base steel.

• Fluxing: A flux solution is applied to the steel to assist with the galvanizing reaction.

Galvanizing:

Material is split into smaller basket jigs, before being immersed in molten zinc at a temperature of around 450°C until the temperature of the work is the same as the zinc. During this process the molten zinc reacts with the surface of the steel to form a series of zinc/ iron alloys. These alloy layers protect steel from corrosion in excess of 30–40 years.

Work is rapidly removed from the zinc, before the zinc on its surface solidifies; the basket is placed in a centrifuge and spun for several seconds. This removes excess zinc from the surface and prevents the items sticking together and ensures a smooth finish. Work is then transferred to a quench tank where it is cooled to allow handling.

Inspection:

The galvanized steel is first visually inspected for its appearance and conformity to standard. Batches may then be non-destructively tested for coating thickness and uniformity.