What Is Galvanization?
Galvanizing (or galvanization) is the procedure by which a zinc coating is applied to the outermost layer of a metal, such as iron or steel. Applying a layer of protection to the underlying metal decreases the likelihood of corrosion or tarnishing.
Galvanization is a relatively straightforward process that yields a fairly thin protective coating, generally around 80 µm in thickness.
The process of galvanization differs based on the particular technique employed. Nevertheless, the critical aspect of the procedure is that it typically entails coating iron or steel in zinc metal, which can exist in a solid or particulate form. The iron present in the surrounding metal will react with the zinc upon introduction, forming a securely bonded alloy coating.
The complete galvanizing procedure consists of the following three phases:
- Surface preparation for steel or iron
- The galvanizing process itself
- Surface treatment following galvanization
How Galvanization Protects the Base Metal
At its core, galvanization operates on several key principles:
- Sacrificial Protection: Zinc, being more reactive than steel or iron, preferentially corrodes when the coating is damaged, safeguarding the underlying metal.
- Zinc Barrier: The zinc coatings form a physical barrier, preventing corrosive substances from reaching the base metal.
- Chromate Passivation: Chromate can be added to the zinc coat to enhance its corrosion resistance by forming a protective passive layer.
The effectiveness of galvanization hinges on proper pretreatment and post-treatment processes:
- Pretreatment: Surface preparation is crucial for optimal zinc adhesion. Inadequate pretreatment hinders the molten zinc’s reaction with the steel, resulting in an imperfect galvanized film.
- Post-treatment: Proper post-treatment ensures the galvanized film’s integrity and appearance. Inefficient post-treatment compromises the film’s quality, diminishing the value of the galvanized components.
What Metals Can Be Galvanized?
Steel and iron are the most prevalent metals suitable for galvanization. Other varieties of metal, nevertheless, are galvanizable. Generally, this treatment applies to ferrous metals such as cold-rolled steel, hot-rolled steel, cast iron, and malleable iron.
Many other materials, however, are unable to acquire galvanized coatings. The galvanization reaction is highly dependent on the presence of iron. Therefore, metals such as copper or aluminum are incompatible with galvanized coatings.
Types of Galvanization Techniques
Among the diverse galvanization methods, hot-dip galvanization and electro galvanization stand out as the most widely adopted approaches. These two methods and other galvanizing processes are discussed below:
Hot-Dip Galvanizing
Hot-dip galvanizing is the cornerstone of galvanization techniques. It involves immersing metal in a molten zinc bath maintained at around 860°F (460°C). This immersion initiates a metallurgical reaction between zinc and the receiving metal.
Upon extraction from the bath, the metal reacts with atmospheric oxygen, causing the pure zinc to form zinc oxide. Further interaction with carbon dioxide leads to the formation of zinc carbonate, the final protective layer. The telltale sign of hot-dip galvanized steel is the crystalline-like pattern, often called “spangle.”
Electro Galvanizing
Electrogalvanization is a unique approach to galvanization. It does not involve the practice of dipping material in molten zinc. Instead, it harnesses the power of electricity to achieve its protective purpose.
In this method, a zinc bath equipped with a zinc anode and a steel conductor serves as the medium for a current of electricity. The resulting electrochemical reaction produces a thinner protective coating than the hot-dip galvanizing method. However, it imparts a brighter surface finish, making it suitable for cosmetic applications.
Galvannealing
This method is a synergistic blend of hot-dip galvanizing and annealing. Thus, elevates the galvanization process to a new level. Following the conventional hot-dip galvanizing step, the coated metal is subjected to air knives to remove excess zinc.
This is followed by a brief heating in an annealing furnace at 500–565°C. This heating facilitates the diffusion of iron and zinc layers into each other, forming zinc-iron alloy layers.
Sherardizing
This versatile galvanization method is also known as vapor galvanizing, thermal diffusion galvanizing, or dry galvanizing. Its unique process involves heating steel parts to 500°C within a closed rotating drum containing zinc dust.
As the zinc evaporates, it diffuses into the surface of the steel part, forming a strongly bonded coating. Sherardizing proves particularly beneficial for small parts and components requiring internal coating.
Pre-galvanizing
Pre-galvanizing is a method closely similar to the hot-dip galvanization process. However, it differs in its execution timing. Manufacturers carry out this process at the first stage of production. Pre-galvanizing involves rolling sheet metal through a cleaning agent to swiftly prime the material for galvanization.
The metal then embarks on a molten zinc bath immersion, followed by immediate recoiling. This technique rapidly galvanizes steel sheet coils on a large scale. It produces a more uniform coating than traditional hot-dip galvanizing.
Benefits of Galvanized Metal
Galvanized metal is widely recognized for its exceptional corrosion resistance, serving as a fundamental component in numerous industries due to its myriad benefits. These benefits include:
Durability
The galvanized coating applied to sheet metal functions as an impenetrable barrier against corrosion, providing prolonged protection for the underlying steel. Galvanized steel can have an average zinc coating thickness of 85 microns.
This is resistant to wear and guarantees structural integrity for decades. This exceptional longevity satisfies the rigorous rust resistance standards of various applications across industries.
Reliable Coating
The galvanized coating forms a consistent and precisely regulated barrier against corrosion by adhering firmly to the steel substrate. Galvanized steel is highly dependable due to the defined galvanization procedure, which guarantees uniform protection in all applications.
In contrast to paint coatings, galvanization incorporates the metallurgical bond into the steel itself, thereby imparting long-lasting protection.
Cost-Effectiveness
In determining the actual cost of steel protection, it is necessary to account for initial investment and lifetime protection expenses. Galvanization presents itself as an economically viable alternative. It provides adequate corrosion protection without necessitating frequent repainting.
In contrast to the relatively stable cost of galvanization, painting expenditures have increased steadily over time. When delivered, galvanized metal is readily usable, and its initial cost is frequently less than other alternatives.
Swift Turnaround
Galvanization is a straightforward and effective procedure that significantly reduces turnaround time. Efficient galvanizing is a key focus of reputable companies. It guarantees that your steel is coated promptly.
Generally, the galvanization procedure is accomplished in less than twenty-four hours following the completion of the steelwork preparatory phase. Although comprehensive preparation is critical, it is possible to complete it quickly.
Comprehensive Protection
Steel and zinc forge an exceptionally robust alliance during the galvanization process, which ensures steadfast corrosion protection. The combination of this resilient coating and the intrinsic durability of steel guarantees thorough protection for the galvanized surface.
Applications of Galvanized Metal
Galvanized metals have become essential components in different industries, from the robust structures of automobiles and bicycles to the pipelines that transport potable water.
Automotive Sector
The automotive industry has widely adopted galvanized steel as the preferred material for vehicle bodies due to its remarkable resistance to rust. The building block of an automobile is made up of approximately 80% of the galvanized steel.
Automobile manufacturers have strategically capitalized on the rust-resistant attributes of galvanized steel, allowing them to extend warranties against rust perforation.
Solar and Wind Energy Industries
Galvanized steel is a sustainability superpower in the renewable energy sector. Its corrosion resistance renders it an optimal selection for wind and solar projects. In addition, the absence of emissions from hot-dip galvanized steel is consistent with the environmentally conscious practices of these sectors.
Telecommunications Connections
The preservation of phone cables and equipment boxes often depends on galvanized steel. The material’s sturdy construction and ability to withstand corrosion reduce the required maintenance frequency. This guarantees the continued functionality and dependability of communication networks.
Electric Appliances and Equipment
Numerous electrical appliances have galvanized steel casings, attesting to the material’s resilience and protective attributes. Its resistance to harsh environments makes galvanized steel an optimal option for these applications.
Building and Constructions
Galvanized construction steel has been the material of choice in the construction sector due to its remarkable longevity and visual attractiveness. In addition to structural components, galvanized steel can be found in fences, gutters, railings, tubing, and poles.
Conclusion
The numerous advantages of galvanized sheet metal include resistance to corrosion and enhanced durability. Furthermore, it finds utility across numerous sectors and facilitates various applications. However, to ensure optimized results with galvanizing metal, you need to work with the right manufacturer.
AT-Machining provides economical and on-demand prototyping and sheet metal fabrication services. We offer superior results for prototypes and high-volume productions alike. Our primary strengths are our exceptional manufacturing capabilities and swift delivery. Contact us now, and let’s discuss your project further.
