The Journey of Steel in A Hot-Dip Galvanizing Plant
We wanted to prepare a detailed article for you about the Journey of Steel in the Hot Dip Galvanizing Plant, which is a matter of great curiosity.
Table of Contents
Definition and Purpose of a Galvanizing Plant
Agalvanizing plant is a specialized industrial facility where metals, primarily steel and iron, are coated
with zinc through a process known as galvanization. This zinc coating serves as a protective barrier,
shielding the underlying metal from corrosion and greatly extending its service life under exposure to
various types of environments.
Importance in Industrial and Commercial Applications
Galvanizing plants play a pivotal role in numerous sectors, including but not limited to, construction,
automotive, energy, and infrastructure. The corrosion-resistant properties of galvanized steel make it
a preferred material for structural components, utility poles, automotive frames, and countless other
applications where durability is essential.
Below we explain the steps a steel article follows in the process of hot-dip galvanizing.
Pre-Treatment (Cleaning and Surface Preparation)
Before metal components can be galvanized, they must undergo rigorous cleaning. The pre-treatment
section typically includes degreasing tanks, acid baths for pickling, rinse stations, and flux baths. The
nature of this sequence of pre-treatment is explained below:
- Degreasing: This is the first stop of the steel to be galvanized in the pre-treatment process. In
the degreasing tanks, the steel article is purged of oily contaminants that remain from the
manufacturing processes. Degreasing is essential for a good pre-treatment, as oil and grease
on the article affects the performance of both acid pickling and galvanizing. - Pickling: After degreasing, steel articles are immersed in a bath of hydrochloric acid (HCl).
This operation is to eliminate the iron oxide layers and milling scales on the surface of the
article, providing an open surface of steel with which the molten zinc can now react. - Rinsing: Subsequently, the articles are immersed in clean water, which ensures that leftover
acid or any other contaminants from the previous steps do not go any further. This is when a
clean slate is started on the steel surface. - Fluxing: As the final step of pre-treatment, the steel article is dipped in a solution that
consists of water, zinc chloride and ammonium chloride. Zinc chloride protects the uncoated
steel from rust formation until it is galvanized, while ammonium chloride wets and activates
the steel surface rendering it more open than ever to a healthy and efficient reaction with
molten zinc.
Drying
Once pre-treatment is done, wet steel is transferred to the drier. Drying the steel is important, as it
will prevent big splashes of zinc during the galvanizing stage; water reacts viciously with molten zinc.
Galvanizing Furnace and Zinc Bath
At the core of the galvanizing plant is the furnace and zinc bath. The furnace heats zinc to its molten
state, maintaining its temperature about 450°C. Metal components are then immersed in this molten
bath, allowing the zinc to bond metallurgically with the base metal.
Post-Treatment
After galvanization, freshly galvanized articles are cooled, either by hanging in air or quenching, and
undergo post-treatment processes such as passivation to enhance corrosion resistance further.
Quality control inspections ensure that the coating thickness and adherence meet industry standards.
This is how the hot-dip galvanizing process is performed on steel, in a nutshell. If you would like to
learn more about the services ANI Metal provides to hot-dip galvanizers worldwide, contact us for further.