Hot – Dip Galvanizing – Process

STEP -1

For grease & oil removal from the surface of steel, It is immersed in acid based degreaser.

STEP-2

To clean the surface of carry over salts for effective acid cleaning.

STEP-3

The rust scale & mill scale are removed from the surface of the steel by passing it through 15 to 20% conc. HCL.

STEP-4

Steel is again rinsed to remove acid & iron salts.

STEP-5

Steel is then passed through heated zinc ammonium chloride solution to prevent oxidation & ensuring that the surface is prime before molten zinc immersion.

STEP-6

Oxide free steel is immersed in molten zinc at a temperature of 450-460 deg Celsius to form zinc–iron inter-metallic alloy. The period of dip depends on the mass to weight ration of steel item immersed.

STEP-7

The steel immersed in molten zinc is slowly withdrawn & quenched to ensure strong adhesion of zinc coating with the steel.

STEP-8

The steel is then chromate treated for providing passivation protection during transit or during storage of galvanised steels in humid conditions.