If you are looking for a reliable and effective way to coat your steel products, you might want to consider hot dip galvanizing. This is a widely used technique that involves immersing the steel in molten zinc, creating a durable and corrosion-resistant layer. Hot dip galvanizing is not only a great solution for preventing rust but also for enhancing the mechanical performance of your steel. In fact, hot dip galvanizing can significantly improve the scratch resistance and wear resistance of your steel products, making them more suitable for harsh environments. In this blog post, we will explain how hot dip galvanizing works, what are its benefits, and how you can choose the best hot dip galvanizing service for your needs.
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The history of this process goes back to when a French chemist named Melouin discovered that zinc could shield steel from the harmful effects of the environment. However, it was not until the early 19th century that hot dip galvanizing became widely used in industry.
The principle behind hot dip galvanizing is based on the concept of 'galvanic cells', which is why the process is also called galvanizing. When the zinc layer is applied to the steel surface, it creates an electrochemical reaction that prevents rust from forming. Even if the zinc layer is damaged, the steel underneath will still be protected, cathode, and protect itself from corrosion. There are different ways to apply the zinc layer to the steel, but the most common one is hot dip galvanizing, which involves dipping the steel into molten zinc. This method has many advantages, such as uniform coating, and long-lasting protection. However, there are also some disadvantages, such as distortion, and limitations created by the bath sizes.
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Hot Dip Galvanizing Methods
Hot dip galvanizing can be processed via two fundamental methods which are dry galvanizing and wet galvanizing. The difference between the methods comes from the differentiation of fluxing steps for each process. Nonetheless, the initiation and progress of both methods in very similar to each other.
At the beginning of the galvanization process, steel surfaces are cleaned using mechanical methods such as grinding or blasting. Since some marking or painting traces remain on the surface of the steel, removal of these contaminants must be done.
Then, the steel is de-greased in an alkaline solution to remove any oil or grease that might have been applied during transportation or storage to protect against the adverse effects of high salinity environments. Next, the steel is rinsed in hot water and dipped in diluted hydrochloric acid (or sulphuric acid) to remove any mill scales, rust, and oxides. This step is called pickling.
Examples of profiles and structures that are difficult to access for mechanical cleaning. In hot-dip galvanizing, all surfaces receive equally good coating
After the pickling step, steel profiles are immersed in the molten zinc bath. During the dipping process, utilization of the fluxing agent is necessary for most of the operations. The fluxing addition aims to dissolve oxide scales on both steel surfaces and molten zinc. The dissolution of oxide compounds is vital to yield a superior contact between iron and zinc. Here, the addition of the fluxing agent selects the type of hot dip galvanizing. In brief, the fluxing agent can be introduced by implementing either dry galvanizing or wet galvanizing methods.
As a method of hot dip galvanizing, Dry galvanizing is a method of hot dip galvanizing that involves degreasing, pickling, and rinsing steel parts. Once these steps are completed, the steel parts are immersed in a fluxing solution containing zinc-ammonium chloride. After passing through the fluxing bath, the surfaces are dried. The steel surfaces are then dipped into a molten zinc bath where hot dip galvanizing is maintained. When the components are completely immersed in the zinc bath, fluxing residues or oxide compounds are skimmed from the surface of the zinc bath. These residues originate from the fluxing operation, where a thin layer of fluxing salts forms on the surface of the immersed steel sections. After removing the steel pieces from the molten zinc bath, they are cleansed and cooled underwater.
The dry method of hot-dip galvanizing is based on this schematic. However, steel sections can be rinsed between de-greasing and pickling
The wet galvanizing process is another method of hot dip galvanizing. In this process, the molten zinc bath is separated into two sections using a beam. The first section of the bath contains the fluxing agent, which is deposited into the bath (ammonium chloride is widely used as the flux agent). After the pickling step of the hot dip galvanizing process, steel components are immersed in the first section of the bath, where molten zinc contains a flux agent. Thereafter, steel components are taken from the first section of the bath and dipped into the second section. The second section of the bath preserves only pure molten zinc. Flux residues and oxide compounds are skimmed from the surface of the bath in this section. As in the dry galvanizing method, steel sections are cooled in water media.
When examining the two methods separately, both wet galvanizing and dry galvanizing provide substantial quality and corrosion protection. Since the aim of hot dip galvanizing is to protect steel surfaces from corrosion, both methods can be utilized for most processes. However, industrial applications prefer dry galvanizing as the hot dip galvanizing method. The reason for selecting the dry galvanizing method can be explained when time and money are taken into account. Most vendors prefer dry galvanization because of its simplicity.
The wet method of hot-dip galvanizing is based on this theory. However, steel sections can be rinsed between de-greasing and pickling
Iron and Zinc Reactions
The hot dip galvanizing process is used to cover a thin zinc layer on the steel substrate, which results in the formation of intermetallic compounds between iron and zinc metals. Since the temperature of the process is slightly high, the diffusion of zinc atoms through the surface of the steel substrate increases. An increase in the distribution of particles leads to the formation of new compounds between the iron-zinc boundary. The standard temperature of hot dip galvanizing is 460 °C, where pure zinc melts. However, for small parts, this bath temperature increases up to 550-575 °C.
The interaction between iron and zinc generates different iron-zinc layers, with the iron and zinc composition changing from layer to layer. A general investigation of the iron-zinc layer reveals that the iron content decreases outwards from the surface. The outermost layer resulting from hot dip galvanizing contains only pure zinc. The reason for this pure zinc composition of the outermost zinc layer can be explained by the fundamentals of hot dip galvanizing. When steel pieces are taken out from the molten zinc bath, a thin pure zinc layer adheres to the generated iron-zinc intermetallics. The schematic below represents the iron-zinc compounds generated during hot dip galvanizing processes. Note that as thickness and type of layers change, steel surface mechanical properties also change, which may affect the fatigue properties of steel parts. Hence, one may consider this phenomenon if designing steel parts for cyclic motions.
Iron-zinc compounds resulted in hot dip galvanizing
Strength of Hot Dip Galvanized Sections
If you are wondering how hot dip galvanizing affects the strength of steel sections, you are not alone. Many researchers have investigated this question by measuring different properties of steel before and after galvanizing. Key indicators of strength, such as yield strength, tensile strength, and fracture strength, which indicate how much force the steel can withstand without breaking or deforming have been observed in both galvanized and non-galvanized steel samples. The results show that hot dip galvanizing does not change the yield strength or tensile strength of mild carbon steel sections. However, it does slightly reduce the fracture toughness, which is the ability of a material to resist crack propagation.
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Corrosion of Zinc Layers Under Liquid Medium
Hot dip galvanizing is utilized for enhancing the corrosion resistance of steel parts. Hence, the corrosion performance of coated parts is the preliminary subject of the hot dip galvanizing process. When a zinc-coated steel component is immersed in a liquid environment, the steel part is covered with protective corrosion products (mostly impervious oxide scales). Hence, the resultant corrosion products slow down the corrosion rate. However, some alkaline or acidic liquids may remove the resultant layer, which causes an acceleration in the corrosion rate.
Arc Welding of Galvanized Parts
The weldability of hot-dip galvanized products is similar to that of plain carbon steels. In fact, there is no significant difference between zinc-coated and plain carbon steels in terms of weldability. However, welding parameters of plain carbon steel cannot be directly used for coated steel parts due to the presence of the zinc layer. Essential parameters that need to be considered when welding coated steel parts include the thickness, composition, and structure of the zinc layer. Therefore, it is important to take into account the properties of the zinc layer to ensure optimal welding performance.
Whether you need help with your existing galvanized products or you are looking for new ones, we can assist you with our expertise and experience. At YENA Engineering B.V., we offer a range of services and products that use this technique, such as structural steel parts, pressure vessels and hot induction bends. If you are interested in learning more or working with us, visit our website or contact us now.
Hot-dipped galvanized steel is one of the most versatile materials out there. It's strong, durable, and can handle minor bumps and scratches without compromising the integrity of its protective zinc coating. To showcase this, we've compiled a list of seven common uses of galvanized steel. While you may be familiar with some of these applications, others may surprise you.
Galvanized steel materials make up powerful support structures for buildings, especially when they are surrounded by concrete. From apartment and office buildings to stadiums or museums, galvanized steel guarantees a building's frame and interior structure will remain strong and corrosion-free for decades. Its unique zinc coating means it can withstand minor scratches and damage without losing its rust resistance. This is because of zinc's self-healing properties, which we'll cover more in the next section.
Hot-dipped galvanized steel outshines every other material when it comes to strengthening and reinforcing roads and bridges. This is why reinforcing roads is one of the most common uses of galvanized steel While the materials around it crack or wear down over time, the galvanized steel frame remains in like-new condition. There have even been projects where, once the road or bridge was cut, the hot-dipped galvanized steel frame was found stronger than it was when installed. This is because of the zinc coating's self-healing properties, which build up a protective coating when damage to the structure may cause water to seep through the surface.
Building bridges in areas with harsh conditions is one of the most famous uses of hot-dipped galvanized steel. Why is this one of the common uses of galvanized steel? The steel is chosen for two reasons: It promises superior corrosion resistance without compromising aesthetics. Its ability to handle wet, salty environments has made it the first choice of builders and project managers in northern and southern areas alike. Whether it is being used to strengthen highway overpasses in New York or down in the tropics to create a bridge that can withstand ocean waves and hurricanes, hot-dipped galvanized steel outperforms expectations every time.
Galvanized steel even transformed a small US town into an up-and-coming center of commerce after the town became home to a bridge that defied logic. You can read more about that bridge in our blog post here.
Galvanized steel is common in industrial processes. While this use may not garner as much media coverage, it plays an important role in supporting American production. The reason this is one of the common uses of galvanized steel is that the strength and resilience of galvanized steel allow it to be formed into complex shapes for machinery, while its corrosion resistance guarantees it will continue functioning without fail. Galvanized steel plays an essential role in forming equipment and supporting structures for the chemical, oil, energy, pulp and paper industries across the country.
Galvanized steel is a great choice for outdoor monuments and memorials. Because materials of many shapes and sizes can be hot-dip galvanized, stunning sculptures or structures can be built from the resulting galvanized steel. The zinc coating boasts a bright, silver appearance, while its corrosion resistance guarantees it will maintain its beauty for years to come.
From handrails and canopies to solar panels, one of the common uses of galvanized steel is for outdoor structures that serve a daily purpose. Its corrosion resistance and durability mean that the original equipment does not require constant repairs or replacements. This reduces waste and the amount of energy necessary to maintain each piece of equipment. It also means that your equipment and the site where it was installed remain rust-free for years.
Galvanized steel has multiple uses in agriculture, from storage silos to animal pens. Its corrosion resistance means it can handle moisture and harsh conditions common on farms without losing its strength or appearance. Plus, galvanized steel's durability reduces the need for ongoing maintenance and replacements, making it a cost-effective option for farmers looking to invest in durable structures.
At South Atlantic, we take pride in serving many industries across the country by providing quality galvanized materials and hot-dip galvanizing services. We're well-versed in the common uses of galvanized steel and how it can help you on your next project.
Whether you are working on a project within one of the industries we reviewed above or have a different build that calls for the durability of galvanized steel, we've got you covered.
You can learn more about our galvanized materials and hot-dip galvanizing services on our website, and contact us using this link: southatlanticllc.com/contact.
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