Galvanization and galvannealing are coating processes that involve coating a sheet metal part with zinc. Both are intricate sheet metal fabrication processes used in several industries. However, they have different functions, processes, acceptance, and outlook, which affects their popularity. For example, most people know more about galvanization than galvannealing due to its presence in most chemistry textbooks.
Both processes are applicable for coating steel with the formed galvanized and galvanneal steel having high strength, corrosion resistance, and durability. This makes both types of materials important in making several industrial products. However, selecting the right one can be a challenge because of both sheet metals’ unique properties. Therefore, there is a need to understand the galvanneal vs galvanized steel comparison by knowing their processes, similarities, differences, and uses.
Galvanization is the more common zinc coating process suitable for materials such as steel and iron. The process is essential as it protects the sheet metal parts from corrosion and rust and makes them more durable. There are different galvanizing processes suitable for galvanized coating. Here, we will introduce the most common method (hot-dip galvanizing) while giving an idea of what the others entail.
Hot Dip Galvanizing
Hot-dip galvanizing is the most common way of making galvanized steel. It generally involves dipping the steel metal part in molten zinc to form a coating. Here are the general steps.
· Step #1: Cleaning
The steel part must not contain impurities such as grease, fat, oil, wax, etc. Therefore, the first step is to clean the material. For example, you will remove impurities such as grease, fat, and oil using degreasing solutions. Depending on the impurities you suspect, there are other methods of cleaning the steel materials.
· Step #2: Pickling
Pickling is an essential step that helps prepare the steel metal part for maximum adhesion of the zinc coating. Pickling occurs majorly by lowering the part into a hot diluted oil of vitriol.
· Step #3: Fluxing
Fluxing improves the adhesion process by using a saline solution such as zinc-ammonium chloride to enhance the steel-zinc bonding.
· Step #4: Galvanization
After fluxing, galvanization occurs by dipping the steel metal part in a vat of molten zinc (at about 8500F. The zinc and metal form an external molecular bond that protects the metal.
· Step #5: Post Processing
After galvanization, we inspect for the consistency of the coating in terms of completion, thickness, etc. For example, after galvanization, thickness control occurs by using air knives. Some post-processing processes also include painting (although galvanneal steel is the more common type for painting).
Other Galvanization Processes
While hot-dip galvanization is the most common process of making galvanized steel, there are other methods of producing it. Below are the common types:
· Thermal Spray (Or Metallizing)
Thermal spraying involves preparing the part using grit blasting or any other suitable method to improve adhesion and spraying the sheet metal part with semi-molten zinc using arc spray or plasma heat source.
With thermal spraying, it is possible to control the thickness. It is also possible to galvanize sheet metal parts with complex and inaccessible designs. The galvanized zinc has both barrier and cathodic protection. However, thermal spraying is more expensive.
Electroplating is a chemical method on its own, but you can tweak it to galvanized steel parts. The method involves putting the sheet metal you want to coat at the cathode and the zinc metal part at the anode. The electrolyte is a zinc salt solution in the tank, and the anode and cathode will be in the solution. On passing power through the setting, galvanization occurs. Electrogalvanization is economical, versatile, and effective in galvanizing small metal parts such as fasteners.
Sherardizing is another method you can use. Here, you place the steel part in a rotating drum containing zinc dust and sand as a filler. You then heat the rotating drum above the zinc melting point and below the steel’s (about 3800C). The heat melts the zinc, which diffuses to the steel part, forming the Zn-Fe bond hence the galvanization.
Advantages of Galvanization (Hot-Dip Galvanization)
Steel is an important material in several industries due to its ease of custom prototyping. However, with galvanization, it becomes stronger, durable, etc. Therefore, galvanization is a popular sheet fabrication method used by different industries in different capabilities. Below are a few of its advantages.
· Less Maintenance and Low Long Term Cost
Hot-dip galvanizing has a lower cost than other coating techniques such as painting, electroplating, etc. Also, unlike other methods, eventually, galvanized steel doesn’t undergo much maintenance, reducing long-term costs.
· Long Life
Galvanized steel has a long life expectancy, with structural parts reaching at least 50 years in rural areas and 25 years in urban areas.
· Tough and Reliable Coating
The zinc coating of the steel ensures it is more durable and stronger. Therefore, there is a lower chance of mechanical damage before, during, and after use. Also, the process is reliable as it is easy to decide the coating of the steel parts, which is important in the coating and the effective functioning of the parts.
· Automatic Protection
Aside from the tough coating, the galvanization ensures the protection of the steel part from environmental damage. It does this by acting as a cathodic/sacrificial. Also, it does not require touch-up, unlike other organic coatings.
Galvannealing is similar to galvanizing, but it adds to the annealing process. Using the hot-dip galvanization, after cleaning, pickling, fluxing, and galvanizing, you anneal the sheet metal part by heating it to about 10500F in an annealing oven.
The annealing process melts the iron part of the steel. The melted iron travels to the outermost part and forms an alloy with the zinc coating. Consequently, galvanneal steel parts are more durable, weldable, and less susceptible to damage than galvanized steel. Other post-processing procedures you can also introduce include temper rolling for a smooth surface.
Galvannealed steel has an “A” designation. Each has its properties and applications, with the popular one being the A40 vs A60 galvannealed steel.
A40 has a thin galvannealed coating (0.40 oz per square foot), providing surface protection and formability. While A60 has more coating (0.60 oz per square coating) and is better for more surface protection.
Advantages of Galvannealing
- Better formability and weldability (especially spot-welding)
- High better paintability when compared to standard galvanized parts
- Less susceptible to rusting
- High corrosion resistance with minimum yield strength
Typical Uses of Galvanized Steel Products
Galvanized steel parts are suitable for making many industrial and common products. Here are examples of typical uses of the parts.
· Automotive Industry
Galvanized steel parts are applicable in making the body of several automobiles such as cars and bicycles. This is because the durability, aesthetics, and corrosion resistance complement automobiles’ external environment most likely used in.
· Nuts, Bolts, and Other Tools
Galvanized steel is applicable in making small structural steel products used in external conditions such as Nuts, bolts, tools, and wires.
· Construction Industry
Due to the corrosion and rust resistance and durability, galvanized steel parts are suitable for making the structural components in the construction industry. For example, it is common in making structures like balconies, verandahs, staircases, ladders, walkways, fences, roofs, outdoor walkways.
· Energy Sector
One of the principles of energy sources is continuity, and one of its main natural determinants is the need for maintenance. Galvanized steel requires next to nothing maintenance. Therefore, it is suitable for making electrical wires, solar wires, etc. Also, it is environmentally friendly.
· Agriculture Sector
Most equipment used in agriculture is used in the external environment. Therefore, there is a need for galvanized products as they are less prone to rust and corrosion. In addition, galvanized steel can survive for decades in good and harsh environments.
Typical Uses of Galvanneal Steel Products
Galvanneal steel products based on their better properties are also applicable in the same setting as galvanized steel. However, their better properties are also applicable in other settings. Here are typical uses of the products.
· Automobile Industry
Car manufacturers such as Honda, Toyota, and Ford use galvannealed parts in making their car frames. Depending on the design, they use a different galvanneal steel based on the “A” designation.
· Waste Disposal
This type of steel is more durable than galvanized parts, which leads to a lower tendency for maintenance. Therefore, they are suitable for constructing permanent debris and linen chute systems.
Such steels are suitable in deep drawing, forming, high-tensile stress conditions, marine applications, and welding operations.
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Similarities Between Galvanneal vs Galvanized Steel
Even though different, there are some similarities in the galvanneal vs galvanized steel comparison. The common one is that they fall under the ASTM A 653/A 653M category. However, there are other similarities you need to know.
Both galvanized and galvannealed steel with zinc coatings prevent rust and corrosion resistance. They are also very durable, making them suitable for making different structural products. However, galvanneal steel is more rust and corrosion-resistant than galvanized steel.
Using the hot-dip galvanization process, both produce a coating of the same weight. However, galvanneal steel differs in composition (see next part).
Differences Between Galvanneal vs Galvanized Steel
Before choosing either galvanneal or galvanized steel, you should be familiar with their differences. Here are a few differences between both types of steel.
Galvanized steel has a coating made up of majorly zinc material. However, it might also contain a small part of iron (a constituent of stainless steel). On the other hand, the annealing process makes steel have three layers of coating (zeta, delta, gamma) – based on the amount of iron in the latter. Gamma is the closest to the steel part, and it contains the highest level of iron. Also, when compared to galvanized steel, the coating is stronger, which means the galvanneal steel is harder and more durable.
Galvanized steel parts have a shiny metallic appearance, while galvanneal steel parts have a dull gray matte appearance because the annealing process forms the Zn-Fe alloy.
The presence of iron in the galvanneal steel coating makes it more weldable than galvanized steel. Therefore, galvannealed steel has better spot welding characteristics than galvanized steel. Also, they have better electrical resistance, hardness, and melting point.
Galvanized steel has a more porous surface, making it more paintable than the other. In addition, the porous surface removes the need for sanding and allows for better adhesion.
Galvanized steel has a softer coating, making it easy to machine by manufacturing processes such as CNC machining. Galvannealed steel, on the other hand, is strong and highly ductile due to the annealing, and they have higher formability.
Galvanneal parts are costlier than galvanized steel parts due to the extra step (annealing). Also, its market value/cost is higher since it has better rust and corrosion resistance, weldability, formability, etc.
A table briefly presenting differences:
|Three zinc-iron layer
|One zinc layer
|Dull gray matte appearance
|Shiny metallic appearance
|Ideal for spot welding
|Higher Corrosion resistance
|High Corrosion resistance
Choose the Right Steel for Your Project
Knowing the right steel to pick from the galvanneal vs galvanized steel comparison can be challenging due to its unique properties. While this article introduced both types of zinc coating processes regarding mechanisms, similarities, differences, and uses, this might not be enough as you need an expert hand to guide you in selecting one.
At Rapiddirect, we have a team well experienced in sheet metal fabrication that can help you choose the right one galvanneal vs galvanized steel. Aside from advising you, RapidDirect is committed to providing professional sheet metal fabrication services for customers worldwide. As a result, we have manufactured numerous prototypes and parts that meet our value customers’ high-quality standards and needs. In addition, we promise up to 30% additional price reduction and fast lead time. Just upload your design file now and get a quote and DfM analysis within 12 hours.
No, galvanized steel and stainless steel are different. Their differences arise in their protective coating. On the one hand, galvanized steel gets its protective coating by dipping into molten zinc. On the other hand, stainless steel has its protective part. The difference in coating mechanism makes stainless steel more expensive and stronger.
No, it is not advisable to use galvanized steel and stainless steel together. One would trigger the other to corrode. On the one hand, stainless steel will have a slow rate. On the other hand, galvanized steel would have a faster corrosion rate.
Yes, galvanized steel is stronger than regular steel. In addition, the presence of the protective zinc layer makes the galvanized steel stronger and more durable than regular steel.