Difference Between Galvanized and Hot Dip Galvanized

The key difference between galvanized and Hot Dip Galvanized is that most galvanized materials have a smooth and sharp finishing, whereas hot sip galvanized structures have a rough finishing.

Galvanization is a process of preventing metal surfaces from corrosion. After the completion of galvanization, we say that the surface is “galvanized” if it is done via the usual procedure. However, if we use hot dipped method, we call it a “hot dip galvanized surface”.

CONTENTS

1. Overview and Key Difference
2. What is Galvanized 
3. What is Hot Dip Galvanized
4. Side by Side Comparison – Galvanized vs Hot Dip Galvanized in Tabular Form
5. Summary

What is Galvanized?

A galvanized surface is a metal surface that has a zinc layer for the protection from corrosion. We call the process of applying this zinc layer “galvanization”. Moreover, this application is done on steel or iron surfaces.

There are different types of galvanization, including:

• Hot dip galvanization – immersion of the item in molten zinc
• Continuous galvanizing – a form of hot dip galvanization, but this method forms a thinner zinc layer; thus, the corrosion resistance is comparatively less
• Thermal spray – spraying semi-molten zinc on to the item
• Electroplating – using the item and zinc metal as electrodes in an electrochemical cell
• Mechanical plating – electroless method to deposit the coating using mechanical energy and heat

What is Hot Dip Galvanized?

Hot dip galvanization is the process of coating a zinc layer on a metal in order to protect that metal from corrosion. We can denote it as HDG. This process has three major steps, as follows:

1. Surface preparation
2. Galvanizing
3. Inspection

In the surface preparation step, we have to hang the steel item using wires or place in an appropriate rack. Thereafter, the steel goes through three cleaning steps: degreasing, pickling and fluxing. The degreasing step removes the dirt on the steel surface. Pickling step removes mill scale and iron oxide. Later in fluxing step, it removes any other oxides present on the steel surface and forms a protective layer which can avoid any further oxide formations.

During the galvanizing process, we need to dip the steel in a molten bath of zinc, which has at least 98% zinc. Here, the iron in the steel surface tends to form a series of zinc-iron intermetallic layers and an outer layer of pure zinc. In the step of inspection, we need to inspect the coating. Moreover, we need to determine the quality of the surface zinc layer.

What is the Difference Between Galvanized and Hot Dip Galvanized?

Hot dip galvanizing is a type of galvanizing. The key difference between galvanized and hot dip galvanized is that galvanized materials have a smooth and sharp finishing, whereas hot sip galvanized structures have a rough finishing. Furthermore, the process of galvanizing includes the formation of a layer of zinc for the protection of the metal from corrosion while hot dip galvanization includes the formation of a pure zinc layer on the surface of the metal via surface preparation, galvanizing and inspection.

Summary – Galvanized vs Hot Dip Galvanized

In brief, hot dip galvanizing is a type of galvanizing. The key difference between galvanized and hot dip galvanized is that galvanized materials have a smooth and sharp finishing, whereas hot sip galvanized structures have a rough finishing.

Reference:

1. “What Is Hot-Dip Galvanizing?” American Galvanizers Association, Available here.
2. “Types of Galvanizing and Other Zinc Coatings.” Galvanizers Association of Australia, Available here.

Image Courtesy:

1. “Image from page 195 of “The modern electroplater; a complete book considering fully the elementary principles of electro deposition of metals, their practical application and industrial use” (1920)” By Internet Archive Book Images (No known copyright restrictions) via Flickr
2. “Feuerverzinkerei 3” Oleh Sarang – Karya sendiri (Domain Publik) via Commons Wikimedia