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Hot-Dipped Galvanized vs. Galvanized Steel: What Is the Difference?

Xomety X
By Team Xometry
December 13, 2023
 9 min read
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Although the terms galvanized steel and hot-dipped galvanized steel are sometimes used synonymously, they refer to different steel coating techniques. Hot-dipped galvanization involves submerging the steel in molten zinc, whereas galvanized steel is coated with a protective layer of zinc through electroplating. 

The main difference is in how they are applied; hot-dipped coating offers a stronger, thicker layer that works especially well in abrasive situations. Conversely, less demanding circumstances are appropriate for galvanized steel. Choosing the appropriate material for production or building requires an understanding of these differences.

This article will discuss the difference between hot-dipped galvanized steel and galvanized steel in terms of purpose, process, advantages, and disadvantages.

What Is Hot-Dipped Galvanized Steel?

A specialized procedure known as hot-dipped galvanizing involves immersing clean steel in molten zinc. Layers of zinc-iron alloy are produced by the metallurgical interaction of iron and zinc. Because of this reaction, a strong covering is created, which eventually becomes a part of the steel itself. The complete coating provided by the immersion in molten zinc offers improved resistance to corrosion and a shield against external influences. With this process, robust steel is produced that may be used in a variety of manufacturing and construction applications.

What Is the Purpose of Hot-Dipped Galvanized Steel?

The purpose of hot-dip galvanization is to prevent corrosion in metal. This method creates a protective coating that stops corrosion by submerging steel or another metal in molten zinc. The sacrificial nature of zinc further protects the underlying material from external factors. This process, which is well-known for its effectiveness, provides a strong and long-lasting barrier against corrosion, making it the go-to option in many sectors in which longevity in a metal is essential.

What Are the Advantages of Hot-Dipped Galvanized Steel?

Hot-dipped galvanization boasts various advantages such as:

  1. Total Coating: Uniform coating protects all surfaces, including edges and corners.
  2. Efficiency: Rapid process compared to time-consuming paint application.
  3. Economical and Eco-Friendly: Ensures steel’s longevity, reducing maintenance costs and environmental impact.
  4. Corrosion Protection: Forms a zinc layer—acting as an initial barrier and evolving into a zinc patina over time.
  5. Reusability Ease: Galvanized structures can be melted and repurposed without quality loss.
  6. Recycling: Fits into a circular economy, with zinc and steel being recycled for continuous use.

What Are the Disadvantages of Hot-Dipped Galvanized Steel?

Some disadvantages of hot-dipped galvanized steel include:

  1. Limited Application Locations: Confined to galvanizing plants; on-site application is impractical.
  2. Size Constraints: Component dimensions are restricted by zinc bath size; refer to industry guidelines.
  3. Potential for Warping: Risk of distortion in large, flat sheets or slender beams due to high molten zinc temperature.
  4. Specialized Welding Procedures: Welding galvanized steel may require different procedures, involving coating reconditioning around the weld.
  5. Color Alteration Complexity: Changing the zinc coating color requires additional painting.

What Is Galvanized Steel?

An electrolyte solution is used in place of a zinc bath during the process of coating steel to create galvanized steel. Zinc ions are converted into a metal layer that sticks to the steel. This happens due to the electric current which is applied to the solution-immersed steel during treatment. Though the thinness of the material leaves it susceptible to corrosion over time, this scientific process yields a protective zinc covering. Steel is more resilient to environmental deterioration thanks to this novel galvanizing technique.

What Is the Purpose of Galvanizing?

The purpose of galvanizing is to provide corrosion resistance to steel. A protective barrier is formed by coating steel with a thin layer of zinc through an electrochemical process. Zinc sacrificially corrodes before steel, preventing rust and corrosion. This method significantly extends the life span of steel structures, making them more durable in various environments. Galvanized steel finds extensive use in construction, automotive, and manufacturing industries, in which resilience to the elements is crucial for longevity and performance.

What Are the Advantages of Galvanized?

Galvanizing offers some significant advantages for structural steel protection:

  1. Ease of Inspection: Visual assessment and non-destructive testing.
  2. Less Maintenance/Lowest Long-Term Cost: Minimal upkeep, cost-effective over time.
  3. Accelerated Assembly Time: Ready for immediate use upon arrival.
  4. Extended Life Span: Exceeds 50 years in rural environments, 20–25 years in urban exposure.
  5. Dependability: Conforms to Australian/New Zealand Standard 4680, with consistent coating thickness.
  6. Complete Protection: Covers all parts, including recesses and corners.

What Are the Disadvantages of Galvanized?

Some disadvantages of galvanized steel include:

  1. Higher Cost: Galvanized steel is often more expensive compared to other methods such as the use of sealant or paint due to the increased production cost associated with zinc coating.
  2. Rust Potential: Susceptibility to rust over time, particularly when exposed to certain chemicals or environments, affecting its life span.
  3. Welding Challenges: Zinc plating can complicate welding, requiring professional consultation for projects involving galvanized steel.
  4. Limited Corrosion Protection: Provides limited long-term protection against corrosion compared to alternative methods like stainless steel.
  5. Toxicity Concerns: The zinc used in galvanizing can be toxic if inhaled or ingested, releasing harmful toxins into the environment when it corrodes.
  6. Regular Maintenance: Requires periodic replacement of the zinc layer and cleaning to prevent corrosion and the accumulation of dirt and grime.

How To Choose Between Hot-Dipped and Galvanized?

The particular needs of the application will determine whether to use galvanized or hot-dipped steel. Steel is submerged in molten zinc during the hot-dip galvanization process, which produces a thicker coating ideal for heavy-duty applications. Galvanizing, on the other hand, produces a thinner coating that is perfect for general applications by using an electrolyte solution. Think about things like the project budget, the environment, and the requirement for increased corrosion resistance. For less-demanding applications, galvanizing offers a cost-effective solution that balances protection, while hot-dipped is best suited for harsh conditions.

How Do Hot Dipping and Galvanization Differ in Their Processes?

Hot-dipped galvanizing and galvanizing differ in their processes. Hot-dipped galvanizing involves immersing steel in molten zinc, to form a thick, robust coating through a metallurgical bond. This process requires heating the zinc to a liquid state, ensuring complete coverage when dipping the steel piece. Galvanizing, on the other hand, utilizes an electrolyte solution in which steel is immersed, and an electric current converts zinc ions into a thin protective coating. The key distinction lies in the application method: hot dipping involves molten zinc, while galvanizing relies on an electrolyte solution and electrochemical reactions.

What Is Hot-Dip Galvanizing and Galvanizing Used For?

Many industries use galvanizing and hot-dip galvanizing to prevent corrosion. The thicker coating that results from immersing steel in molten zinc is what makes hot-dip galvanizing ideal for heavy-duty uses including: buildings, bridges, and marine structures. Galvanizing is appropriate for a variety of applications, including: outdoor constructions and domestic objects. It uses an electrolyte solution to create a thinner coating. The application technique and consequent coating thickness are the primary differences: galvanizing offers a cost-effective and protective balance in less severe situations, while hot-dipped galvanizing offers strong protection in tough environments.

What Are the Properties of Hot-Dipped Galvanized and Galvanized Steel?

Table 1 below highlights the properties of hot-dipped galvanized steel and galvanized steel:

Table 1. Properties of Hot-Dipped Galvanized Steel and Galvanized Steel
PropertyHot-Dipped GalvanizedGalvanized
Property
Coating Thickness
Hot-Dipped Galvanized
Thick coating for heavy-duty use
Galvanized
Thinner coating for general use
Property
Application Method
Hot-Dipped Galvanized
Immersion in molten zinc
Galvanized
Electrolyte solution and electric current
Property
Corrosion Resistance
Hot-Dipped Galvanized
High resistance in demanding environments
Galvanized
Adequate protection for less harsh conditions
Property
Suitability
Hot-Dipped Galvanized
Heavy-duty applications, e.g., construction, marine
Galvanized
General uses, e.g., household items, outdoor structures
Property
Cost
Hot-Dipped Galvanized
Potentially higher due to thicker coating
Galvanized
Generally more cost-effective

Is Hot-Dipped Galvanized Steel More Rust-Resistant Than Galvanized Steel?

Yes, hot-dipped galvanized steel is generally more rust-resistant than galvanized steel. The thickened coating produced by the hot-dipping method offers better protection, particularly in abrasive situations such as many industrial or marine uses. This thicker coating provides longer endurance by functioning as a strong barrier against corrosion. Both techniques provide corrosion protection, however, hot-dip galvanizing is more effective in preventing rust over time due to its higher thickness as opposed to electro-galvanizing's thinner coating.

What Is the Life Expectancy of Galvanized Steel?

The life expectancy of galvanized steel exceeds 50 years in rural environments and ranges from 20 to 25 years in urban exposure. In comparison, hot-dipped galvanized structural steel boasts a longer life span, with an expectation of 80+ years in rural settings and 60+ years in suburban areas. The superior longevity of hot-dipped galvanized steel can be attributed to its thicker coating, providing enhanced corrosion resistance and durability in more challenging environmental conditions.

What Are the Materials Suitable for Hot-Dipped Galvanizing?

Iron, carbon steel, and alloy steel are among the materials that can be hot-dip galvanized. Heavy-duty applications—including: structural steel, bridges, and industrial components—are great candidates for this procedure's effectiveness. Mild steel and iron are both suitable for galvanizing, which uses an electrolyte solution and electric current. Both techniques prevent corrosion, but hot-dip galvanizing is recommended for stronger applications because of its thicker coating, which guarantees greater resilience and longevity in harsh settings.

Does Hot-Dip Galvanizing Weaken Steel?

Yes, the process of hot-dip galvanizing can weaken structures made of high-strength steel. This is ascribed to the heat that is added during the galvanization process, which may change the microstructure and cause a degree of weakening. Although hot-dip galvanizing is a good corrosion protection method, its effects on high-strength steel should be carefully considered in engineering applications. When selecting hot-dip galvanizing for certain steel constructions, it is important to weigh the advantages of increased durability against the possibility of strength reduction.

To learn more, see our article on What is Steel?

Is Hot-Dipped Galvanized Steel Good for Outdoor Use?

Yes, hot-dipped galvanized steel is a great material to use outside. The procedure involves submerging steel in molten zinc. This creates a strong corrosion-resistant layer. In comparison to hot-dipped galvanized steel, regular galvanized steel may not be as resilient to corrosion over an extended period of outdoor exposure. By applying a thicker and more durable zinc coating, the hot-dipping procedure improves the steel's resistance to adverse weather and conditions. Hot-dipped galvanized steel is often chosen for prolonged outdoor use due to its exceptional resistance to corrosion and endurance.

Summary

This article presented hot-dipped galvanized and galvanized steel, explained each of them, and discussed their key differences. To learn more about hot-dipped galvanized and galvanized steel, contact a Xometry representative.

Xometry provides a wide range of manufacturing capabilities and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.

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Xomety X
Team Xometry
This article was written by various Xometry contributors. Xometry is a leading resource on manufacturing with CNC machining, sheet metal fabrication, 3D printing, injection molding, urethane casting, and more.