When embarking on a construction project or manufacturing venture, one of the pivotal decisions you’ll face is selecting the right material. Galvanized steel and aluminum are two popular choices, each offering unique advantages. This article will delve into the properties, applications, advantages, and disadvantages of both materials to help you make an informed decision.
What is galvanized steel?
Galvanized steel, also known as galvanized steel plate or galvanized iron plate, refers to a steel plate coated with a layer of zinc on the surface. Galvanizing is a common metal corrosion prevention method, mainly used to prevent the corrosion of steel. Plating a layer of metal zinc on the surface of steel products can isolate the contact between steel and oxygen and water vapor in the air, thereby avoiding or slowing down the corrosion of steel.
Galvanizing process
There are two main production methods for galvanized steel: Hot-dip galvanizing (hot-dip galvanizing) and electroplating galvanizing (galvanizing).
- Hot dip galvanizing: This is the most commonly used galvanizing method. First, the clean steel product is immersed in the molten zinc solution, so that its surface is attached to a layer of zinc. The galvanized layer obtained by this method is thicker and has strong corrosion resistance, which is suitable for steel products used outdoors and in harsh environments, such as building materials, transmission and transformation towers, communication towers, highway guardrail, Bridges, ships and so on.
- Electroplating galvanizing: In the electroplating pool, a layer of zinc is deposited on the surface of steel products through electrolysis. The galvanized layer obtained by this method is thin, but the appearance is smooth and detailed, and it is suitable for occasions with high decorative and anti-corrosion requirements, such as home appliance shell, auto parts and so on.
What does galvanized steel look like?
The surface of galvanized steel is covered with a zinc layer, so its appearance is usually silver or light gray. Moreover, the surface zinc layer thickness of galvanized steel can be controlled according to different needs, generally ranging from 5-25 microns. This layer of zinc is not only beautiful, but also can effectively isolate the steel from the outside oxygen and water vapor contact to prevent rust.
Properties of galvanized steel
The performance of galvanized steel is mainly reflected in the following aspects:
- Corrosion resistance: Galvanized steel plate surface coated with a layer of zinc, zinc has a strong corrosion resistance, compared with ordinary cold rolled steel plate, galvanized steel plate surface hardness is high, can enhance the strength and wear resistance of the steel plate, improve the service life of the steel plate.
- Mechanical properties: Galvanized steel plate has good processing properties, can be bent, stamping, shearing and other processing processes, without affecting the overall performance of steel.
- Physical characteristics: The weight of galvanized steel plate is about 10% heavier than that of ordinary cold-rolled steel plate, and the elongation is about 1.5-2 times, which is slightly lower than that of ordinary cold-rolled steel plate, but its tensile strength is very high.
- Chemical composition: The chemical composition of galvanized flat steel (a form of galvanized steel) includes carbon (C), silicon (Si), manganese (Mn) and other major elements.
- Other features: Galvanized steel has excellent fire resistance, and its surface coating can effectively slow down the spread of flame and protect the safety of buildings.
- Special properties (for aluminum-plated zinc steel plate) : aluminum-plated zinc steel plate is similar to hot dip galvanizing in terms of processing properties, and can meet various processing requirements. Aluminized zinc steel plate has excellent corrosion resistance, and its service life is 2-6 times that of ordinary galvanized steel plate.
What is the use of galvanized steel?
Galvanized steel is widely used in many fields because of its excellent corrosion resistance and mechanical properties. It is usually used in construction, automobiles, electronics, manufacturing, transportation and other fields. For example, galvanized steel is widely used in automobile manufacturing, such as body, door and other parts, which can effectively prevent rust and improve the durability of the car. It is also used in aircraft shell, engine support, maintenance equipment and other parts to increase its corrosion resistance and extend its service life.
Examples of galvanized steel
Examples of galvanized steel are rich and varied, and the following are some common products made with galvanized steel:
- Used for building exterior wall, roof, wall panel, etc. For example, hot dip zinc steel plate (SGCC) is used as the column and force material in glass curtain wall, marble curtain wall and aluminum curtain wall.
- Body panels, doors, chassis brackets, suspension systems, etc., are also galvanized to improve the durability and safety of components.
- Galvanized steel is often used in the manufacture of refrigerators, washing machines, air conditioners and other home appliance shell manufacturing and internal parts, such as brackets, bases, etc.
- In the home, office and construction site and other places, galvanized clips and fasteners are often used for folders, book clips, wrenches, bolts and nuts, etc.
What are the advantages and disadvantages of galvanized steel?
As an important metal material, galvanized steel has its unique advantages and disadvantages. The following is an overview of the advantages and disadvantages of galvanized steel:
Advantages：
- High surface finish: After the surface of the galvanized steel plate is treated, the surface finish is very high and it has a good decoration.
- Good fire performance: galvanized steel plate has good fire performance, and its surface coating can effectively slow down the spread of flame and protect the safety of buildings.
- Strong welding performance: Galvanized steel plate has strong welding performance, can be well connected with other materials, and is widely used in the manufacture of various mechanical equipment and industrial parts.
- Good plasticity and toughness: Galvanized steel plate has good plasticity and toughness, can adapt to various shapes and deformation requirements, but also can maintain good mechanical properties.
- Easy maintenance: Galvanized steel plate is easy to maintain, only need to carry out simple cleaning and maintenance, do not need special treatment.
Disadvantages：
- Not suitable for long-term use: When used in harsh environments or exposed to the atmosphere for a long time, the zinc layer will gradually corrode, resulting in damage to the steel.
- Uneven zinc layer: The zinc layer of galvanized steel is sometimes uneven, which will form a raised “zinc flower”, affecting the beauty. If the zinc layer is dissolved, white substances will appear on the surface of the steel, which will have a certain impact on the storage and aesthetics of the goods.
- High cost: Galvanized steel needs to be galvanized in the production process, which will increase the production cost, so its price will be higher than ordinary steel.
What is aluminum?
Aluminum is a lightweight metallic element with the chemical symbol Al and atomic number 13. It is very rich in the Earth’s crust, second only to oxygen and silicon, and is one of the most abundant metallic elements in the earth’s crust. Aluminum has a range of unique physical and chemical properties that give it a wide range of applications in numerous fields.
Aluminum production and extraction
- Bauxite extraction: Aluminum is mainly extracted from Bauxite. Bauxite is processed by Bayer process to produce alumina (Al2O3).
- Electrolysis method: The process of extracting the metal aluminum from aluminum oxide is called the Hall-Heroult process. The process is carried out in a high-temperature electrolytic cell using an electric current to break down alumina into aluminium and oxygen.
What does aluminum look like?
Aluminum metal usually has a silvery or off-white appearance. Under certain conditions, aluminum will also show different colors, such as black, blue, purple and so on. The production of these colors is related to surface reaction, oxide formation, electrolysis and other factors. For example, when aluminum is oxidized at high temperature in the air, black oxide may appear on the surface; Under certain conditions, a blue layer of alumina is formed on the surface of aluminum. Under very special conditions, aluminum will show a purple appearance.
Types of aluminum
The types of aluminum can be divided according to different classification criteria. The following are several common classifications and the corresponding types of aluminum:
- Pure aluminum: In addition to impurities, the aluminum content is more than 99%. According to the different purity, pure aluminum is divided into high purity aluminum, industrial high purity aluminum and industrial pure aluminum three categories. The purity of industrial pure aluminum is usually between 99.7% and 98.8%, and its grades are L1, L2, L3, L4, L5, L6 and other six kinds. Pure aluminum has the advantages of high electrical conductivity, thermal conductivity and ductility.
- Aluminum alloy: refers to a variety of elements mixed with aluminum in proportion to a metal-like material. Aluminum alloy is usually composed of aluminum and other metals (such as copper, magnesium, zinc, etc.) mixed, according to different alloy composition and manufacturing process, aluminum alloy can be divided into a number of series, such as aluminum copper alloy(2xxx Series), aluminum magnesium alloy(5xxx Series), aluminum zinc alloy(7xxx Series), etc. These alloys give aluminum better properties such as strength, corrosion resistance, and processability.
Related resources: 6061 vs 7075 Aluminum: Which Alloy is Best for Your Project?
Properties of aluminum
- Light weight: The density of aluminum is about 2.7 grams per cubic centimeter, about one-third that of iron or copper. Therefore, aluminum has significant advantages in the aerospace and transportation fields.
- Activity: Aluminum is an active metal that can react chemically with oxygen, water, acid, etc. At room temperature, the surface of aluminum will quickly react with oxygen in the air to form a dense alumina film, which can prevent aluminum from being further oxidized, so aluminum has good corrosion resistance.
- Electrical and thermal conductivity: The electrical and thermal conductivity of aluminum is better, about 60% of copper. This makes aluminum also important in power transmission and heat dissipation applications.
- Ductility and formability: Aluminum has good ductility and can be stretched into thin lines or pressed into sheets. In addition, aluminum’s formability allows it to be easily machined into a variety of shapes.
- Recyclability: The original characteristics of aluminum will not be lost during the recycling process. The recycling of aluminum not only saves resources, but also reduces environmental pollution, and is a sustainable metal material.
What is aluminum used for?
Aluminum has a wide range of uses, mainly due to its light weight, good ductility, electrical conductivity, thermal conductivity and corrosion resistance. Aluminum is used in automotive manufacturing in parts such as body, engine parts and wheels to help reduce vehicle weight and improve fuel efficiency. In addition, aluminum is used to make trains, subways and bicycles. Whether in the high-tech aerospace field, or in the daily use of packaging materials, aluminum has shown its irreplaceable importance.
Examples of aluminum
Examples of aluminum are very rich and involve almost every aspect of daily life. The following are examples of products produced with aluminum materials:
- Used in the manufacture of automobile body, engine parts, wheels and aircraft fuselage, wings, engine parts and so on. The lightweight nature of aluminum helps reduce the weight of cars and aircraft and improve fuel economy.
- The shell and radiator of electronic products such as mobile phones, tablets and laptops are usually made of aluminum, which is both lightweight and beautiful.
- Aluminum doors and Windows, aluminum panels, aluminum honeycomb panels, aluminum tiles, aluminum buckle plates, etc.
- Aluminum POTS, bowls, chairs, tables and other furniture.
What are the advantages and disadvantages of aluminum?
As a common metal material, aluminum has a series of advantages, as well as disadvantages.
Advantages：
- Light weight and high strength: Significantly lighter than steel, reducing the overall weight of structures and vehicles.
- Corrosion resistance: In humid or corrosive environments, aluminum products can maintain long-term stability and durability, reducing the frequency of maintenance and replacement.
- Good thermal and electrical conductivity: the thermal conductivity of aluminum is higher than that of many metal materials, which makes aluminum an efficient heat conduction material.
- Formability: Easier to shape and form, making it ideal for complex designs.
Disadvantages:
- Low strength: Compared with iron, steel, copper and other metals, aluminum strength is low, easy to deformation and fracture.
- Easy to wear: The hardness of aluminum is relatively low and it is easy to be worn. Under certain conditions of use, the service life and performance of aluminum products may be greatly affected.
- Large coefficient of thermal expansion: aluminum is easy to expand or contract at high temperatures. This may lead to dimensional changes and unstable performance of aluminum products.
Galvanized steel vs. aluminum
Galvanized steel and aluminum in many aspects have significant differences. Here is a detailed comparison of the two materials:
Corrosion resistance
From the corrosion resistance point of view, aluminum is significantly better than galvanized steel. Aluminum’s aluminum oxide protective film provides a long-term, self-healing anti-corrosion layer, allowing it to maintain good corrosion resistance in a variety of environments. Although galvanized steel has a certain corrosion resistance, its corrosion resistance will be affected in specific environments (such as high temperature and humidity, organic environment, etc.), which may lead to zinc layer destruction and steel corrosion.
Strength
The strength index of galvanized steel usually includes yield point, tensile strength, elongation and so on. The relative density of aluminum is 2.7, about half that of steel, but its tensile strength can reach 2.0 times that of steel, and the elongation of aluminum is also high, about 20%, indicating that it has good plasticity and toughness.
Therefore, from the point of view of strength, the tensile strength of aluminum is relatively high relative to its weight, that is, aluminum has the characteristics of light weight and high strength. This gives aluminum an advantage in applications where weight reduction is required. However, in applications that require greater pressure and weight, galvanized steel may be more suitable due to its higher mechanical strength and structural stability.
Weight
Considering the weight ratio alone, the preferred material is aluminum. The density of the steel itself is generally between 7.7-8.1 g/cm ³, while the density of the galvanized layer is about 7.14 g/cm ³. The density of aluminum is 2.7g/cm³, which is much lower than that of steel. Therefore, aluminum is more popular in some applications that need to reduce weight (such as aerospace, automotive manufacturing, etc.).
Malleable
In terms of malleable, aluminum is significantly superior to galvanized steel. The ductility of aluminum stems from the characteristics of its atomic structure, that is, under the action of external forces, aluminum atoms can slip or distort relatively easily, so as to change its shape and not easily break, and can be processed into products of various shapes and sizes, such as sheet, pipe, profile, etc. Galvanized steel is steel as a substrate, the surface coated with a layer of zinc alloy material. The ductility of steel is generally lower than that of aluminum, but its specific ductility depends on the type of steel and the alloy composition.
Surface finishing
The surface of aluminum products can be treated in a variety of ways, such as anodizing, spraying, electroplating, etc., to improve its appearance, corrosion resistance or increase functionality. The oxide film of aluminum has the ability to self-repair, even if it is slightly damaged, it can recover quickly, thus protecting aluminum products from further corrosion. The post-treatment of galvanized steel is mainly concerned with eliminating hydrogen embrittlement and enhancing corrosion resistance, and improving its performance and stability through dehydrogenation and passivation treatment.
Thermal conductivity
The thermal conductivity of galvanized steel is generally between 40-52 W/(m·K). At room temperature, the thermal conductivity of aluminum is generally 237-241 W/mK. This value is slightly lower than copper (427 W/mK), but much higher than galvanized steel (40-52 W/(m·K)). Therefore, galvanized steel and aluminum have obvious differences in thermal conductivity, and the thermal conductivity of aluminum is much higher than that of galvanized steel, which makes aluminum more suitable for applications requiring efficient heat dissipation (such as electronic equipment, automotive engines, etc.).
Welding
Galvanized steel and aluminum can both be joined by specific welding methods and processes, and common welding methods include TIG welding, MIG/MAG welding, arc welding and laser welding. However, it should be noted that the melting point of galvanized steel is 419 °C to 450 °C, and the melting point of aluminum is 660°C. The melting point of galvanized steel and aluminum is very different, and it is easy to oxidize in the melting process, and it is difficult to control the melting state of the two in direct welding, which is easy to lead to bad welding.
Rust-resistant
The galvanized layer can effectively prevent steel from contact with the air and slow down rust. In harsh environments, the galvanizing layer may fail, causing the steel to rust. However, in harsh environments such as strong acidity, high humidity, high temperature, and long-term open air, the protective effect of the galvanized layer will be greatly reduced, because the zinc layer may be corroded, resulting in steel rust.
The surface of aluminum is easy to form a dense alumina film, which has a good performance under normal temperature, low temperature, high temperature, wet and other conditions, and can meet the needs of different working environments.
Sustainable development and environmental impact
The production process of galvanized steel will produce wastewater, exhaust gas and solid waste, which may contain harmful substances, such as heavy metals and chemicals, causing pollution to the environment. Promote the use of green galvanizing process, such as electric galvanizing, hot dip aluminum zinc, etc., to reduce environmental pollution.
Aluminum is a renewable material, and the waste generated by its production process can be recycled and reused, which helps to reduce resource consumption and environmental pollution.
Cleanability
The surface of galvanized steel and aluminum is smooth and not easy to accumulate dust and dirt, so it is easier to clean under normal circumstances. However, if the zinc layer is damaged, the steel itself may be more susceptible to corrosion and contamination, increasing the difficulty of cleaning. For the cleaning of galvanized steel, it is usually possible to use ordinary cleaning agents or water for cleaning.
Cost
The cost of galvanized steel and aluminum varies due to a variety of factors, including raw material costs, processing costs, market supply and demand, and so on. Generally, galvanized steel tends to be less expensive than aluminum. The cost of steel itself is lower, and the galvanization process adds a relatively small premium.
The raw material cost of galvanized steel is mainly composed of the cost of steel and galvanized process. Galvanized steel pipe prices range from $800 to $900 per ton, and the average cost of aluminum is about $1,800 / ton. Under normal circumstances, the price of aluminum is higher than that of galvanized steel, the higher cost is due to the more complex extraction and refining processes required to produce aluminum, but the specific price needs to be determined according to market conditions and product specifications.
Is aluminum better than galvanized steel?
Aluminum and galvanized steel each have their own advantages and application scenarios, so it can not be directly determined whether aluminum is “better” than galvanized steel.
Aluminum is a light, corrosion-resistant and easy to work metal. It has excellent thermal and electrical conductivity, which makes aluminum excellent in applications where efficient heat transfer or conductance is required, such as electronic devices and radiators. In addition, aluminum is highly recyclable and environmentally friendly, in line with the concept of modern sustainable development. In the field of construction, aluminum is widely used in doors and Windows, curtain walls and decorative strips because of its beautiful appearance and weather resistance.
Galvanized steel is covered with a zinc layer on the surface of the steel to improve the corrosion resistance of the steel. Galvanized steel has the advantages of high strength, good durability, and relatively low price, so it is more common in applications that require heavy loads or high structural strength (such as Bridges, building structures, etc.). In addition, galvanized steel also shows good weather resistance and corrosion resistance in outdoor environments.
Can aluminum be galvanized?
Aluminum can not be directly galvanized, but it can achieve a similar effect through special treatment. For example, a compound layer of zinc is formed on the surface of aluminum, which can protect the aluminum surface and also provide a better surface treatment for subsequent painting and coloring.
Although it is feasible to galvanize aluminum parts, the process is more complicated and needs to be treated by special process. Because aluminum alloy is easy to soften when heated, the processability is good, but zinc is a strong reducing metal, which is easy to react with aluminum alloy, resulting in unstable galvanizing and falling off.
Electrogalvanizing aluminum requires non-deposition coating treatment, such as passivation, hot-dip zinc plating or anodizing, to form a layer of compounds or pure metals with zinc affinity, and then maintain the stability of zinc during the plating process.
The importance of material selection
Because different materials have different physical and chemical properties, such as strength, hardness, toughness, wear resistance, corrosion resistance, thermal conductivity, electrical conductivity and so on. The right material selection ensures that the product or component can meet the expected performance requirements, such as load bearing, durability, safety, etc. For example, in certain industries, such as food, medical, etc., strict regulations and standards need to be followed to select materials.
Moreover, the cost of different materials varies greatly, including raw material prices, processing costs, transportation costs, etc. Therefore, cost-effectiveness needs to be considered comprehensively when selecting materials. Choosing environmentally friendly, recyclable and degradable materials helps to reduce environmental pollution and waste of resources.
How to choose between galvanized steel and aluminum?
When choosing galvanized steel and aluminum, performance, application scenarios, cost, and specific requirements need to be considered. Galvanized steel has high strength and corrosion resistance, making it suitable for load-bearing and anti-corrosion situations such as buildings and pipelines; Aluminum is lightweight and easy to process, suitable for industries such as aerospace and automobiles that require weight reduction. Based on specific needs, weigh cost and performance, and choose the most suitable material. Here is a comparison table to help you choose suitable materials for different applications.
| Characteristic | Galvanized Steel | Aluminum |
|---|---|---|
| Corrosion Resistance | ✔️ Good (zinc coating) | ✔️ Excellent (natural oxide layer) |
| Tensile Strength | ✔️ High | ❌ Moderate |
| Composition | ✔️ Wide range available | ✔️ Wide range available |
| Weight | ❌ Heavier | ✔️ Lighter |
| Price | ✔️ Less costly | ❌ More expensive |
| Chemical Resistance | ✔️ Good | ✔️ Excellent |
| Hardness | ✔️ Higher | ❌ Lower |
| Durability | ✔️ Better impact resistance | ❌ Lower impact resistance |
| Temperature Resistance | ✔️ Up to 1200°F | ❌ Up to 600°F |
| Machinability | ✔️ Easier | ❌ More difficult |
Conclusion
By carefully considering these factors, you can select the material that best meets your needs and ensures the success and longevity of your project. Galvanized steel offers excellent strength and durability at a lower cost, making it ideal for heavy-duty applications. Aluminum, on the other hand, provides superior corrosion resistance, light weight, and low maintenance, making it suitable for applications where these properties are paramount.
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FAQ
Generally, aluminum is more expensive than galvanized steel due to the more complex extraction and refining processes involved in its production. However, the long-term benefits of aluminum, such as lower maintenance costs and superior corrosion resistance, can make it more cost-effective over the lifespan of a project. It’s important to consider both initial costs and long-term savings when choosing between the two materials.
Both galvanized steel and aluminum are suitable for outdoor use, but they offer different levels of corrosion resistance. Galvanized steel is coated with zinc, which protects it from rust but can wear off over time. Aluminum naturally forms a protective oxide layer, making it highly resistant to corrosion and an excellent choice for harsh outdoor environments, especially in coastal or marine applications.
While it is possible to use galvanized steel and aluminum together in the same project, care must be taken to prevent galvanic corrosion. This type of corrosion occurs when two dissimilar metals are in contact with each other in the presence of an electrolyte, such as water. To mitigate this risk, ensure the metals are properly insulated from each other, use protective coatings, or select compatible fasteners and connectors.
Catalog: Materials Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
