How Hot-Dip Galvanizing Works

Hot-dip galvanizing is essentially a process that coats steel with a protective layer of zinc alloy to protect it from corrosion. Not only is it a relatively simple and cost-effective process, but the resulting benefits will last for decades. Let’s take a look at the galvanizing process from start to finish.

The Process

Preparation

First and foremost, the steel itself must be thoroughly inspected to ensure that drainage and venting requirements are met. It wouldn’t do to have a flawed product at the outset.

Cleaning the Steel Prior to Hot-Dip Galvanizing

Before the galvanizing process can begin, the steel must be cleaned as thoroughly as possible. This isn’t just for appearances. The zinc coating simply can’t bond with a steel surface if foreign materials are present. There are several steps to cleaning:

  1. The steel is submerged into a caustic tank at 180° F to remove any paint residue. It is then rinsed in a freshwater tank at ambient temperature to remove the caustic material.
  2. The steel is pickled by being dipped into a tank of heated sulfuric acid at 140°-145° F to remove any mill scale. Afterward, it is again rinsed in a freshwater tank.
  3. Lastly, the steel is washed in a flux tank containing a mixture of zinc chloride and ammonium chloride at 140°-170° F to provide protection against oxidation before galvanizing.

After these steps have been completed, the steel is ready to receive its new protective coating.

The Hot-Dip Galvanizing Kettle

The freshly cleaned steel is submerged into a kettle of molten zinc at 830°-850° F. The zinc then bonds with the steel in a diffusion reaction, creating a brand-new layer of metallurgically bonded zinc alloy. Before the newly coated steel can be removed from the tank, the surface of the molten zinc must be swept to remove any residue to ensure that the steel is exiting through pure zinc.

Cooling Down

As soon as it’s removed from the galvanizing kettle, the steel is quenched in aqueous sodium dichromate at ambient temperature to help cool it down before the final cleaning process. This also helps the galvanized steel retain its shiny surface for a longer period of time.

Final Cleaning

Once galvanized, the coated surface of the steel is cleaned of any dirt, drip marks or excess zinc to ensure the final product is ready for testing.

Testing Hot-Dip Galvanizing Results

The steel is then moved outside and placed on poles for millage tests. These tests verify that the process was successful and that the zinc coating is the proper thickness. Different applications for the steel can call for different coating thicknesses.

Other Key Considerations for Hot-Dip Galvanizing

Protection Against Rust via Hot-Dip Galvanizing

The main purpose of hot-dip galvanizing steel is to protect it against rust, the natural predator of steel. One of the main benefits of the zinc alloy coating, other than generally being very resistant to abrasion, is that zinc and rust are inherent enemies. Rust simply can’t eat through zinc, so it follows that it can’t eat the steel beneath the zinc. either.

A Long History of Hot-Dip Galvanizing

Galvanizing metal with zinc is a process that we’ve been using for over 150 years. The first known use was in 17th-century Indian armor, and the process was industrialized to protect the iron in British naval ships. Since then, it’s caught on in almost every application of steel and iron throughout the developed world.

Aesthetics

The crystallites of the zinc coating, or the grain, are a visible feature of galvanized steel. This feature is called “spangle” and can be varied and adjusted to taste by altering the number of particles added in heterogeneous nucleation, as well as the cooling rate during the hot-dip galvanizing process. If desired, the spangle can be made to appear uniform, and the grain will be too small to be seen with the naked eye.

Common Uses for Hot-Dip Galvanizing

Hot-dip galvanizing of steel is most often used for construction purposes. The process provides protection for building frameworks, walkways, staircases and more in major cities all around the world. Most of us have almost assuredly come in contact with hot-dip galvanized steel without even realizing it.

Galvanized piping is also used heavily in irrigation and other outdoor water storage and water transportation solutions due to its superior ability to withstand the corrosive forces of the elements and resistance to rust.

The Cost-Effectiveness of Hot-Dip Galvanizing

Hot-dip galvanizing is popular amongst farmers, engineers, architects and more for its protective qualities, but it also provides other more economic benefits.

Because of its longevity and toughness, hot-dip galvanized steel requires less maintenance and can span decades before needing to be repaired or replaced. The resistance to abrasion also makes for smoother surfaces that are more easily cleaned and painted.

Follow us on social media for the latest updates in B2B!

Image

Latest

innovations in healthcare
Innovations in Healthcare: A Discussion with Dr. Craig Joseph at HIMSS 2024
May 24, 2024

Innovations in healthcare were easy to spot at the recent HIMSS 2024 conference. Healthcare Rethink’s Brian Urban caught up with one of those innovators for a live discussion at HIMSS 2024. podcast, Their conversation opens a window and dialogue into the cutting-edge trends reshaping healthcare technology today. This episode features Dr. Craig Joseph, the…

Read More
Preventing burnout
Achieving Professional Growth and Preventing Burnout: The Importance of Time Management and Support Networks in a Fast-Paced World
May 23, 2024

In today’s fast-paced world, balancing professional growth with personal well-being is more crucial than ever. With the rise of remote work, digital transformation, and the constant hustle culture, finding this balance has become a significant challenge for many. A survey conducted by Deloitte suggests that a whopping 77% of professionals experience burnout at work….

Read More
Fan-Centric Business Transformation
Prop Room
May 23, 2024

In this episode of the Fans First series, Jesse Cole, the mastermind behind the Savannah Bananas, shares with us that in the vibrant world of marketing, creativity knows no bounds—a philosophy embodied by a prop room and studio teeming with eclectic costumes and outlandish ideas. This creative hub, seemingly disconnected from conventional themes like bananas,…

Read More
Ace Gardner and Jacob Lewis discuss NIL Deals and Transfer Portals
NIL Deals and Transfer Portals are Also Impacting College Staff and Their Roles
May 23, 2024

College sports is undergoing a significant transformation with the advent of Name, Image, and Likeness (NIL) rights and the increasing prevalence of transfer portals. These changes are reshaping how college staff operate, presenting both opportunities and challenges. With the rise of NIL deals and transfer portals, understanding the behind-the-scenes impact on college coaching staff…

Read More