Galvanneal vs. galvanized steel is typical metal manufacturers use in different applications. These steel types have protective layers, making them strong, corrosion-resistant, and cost-effective alternatives to most metals. Therefore, it would help to understand these steel types’ properties, benefits, and drawbacks to know the best choice for your project.
Overview of Galvannealed Steel
Galvanneal steel is a typical sheet metal coated with a zinc-iron layer, preventing the underlying sheet from corrosion. The production processes used to make galvannealed steel include hot-dip galvanizing and annealing. Hence, the term “galvanneal” is formed through the combination of “galvanize” and “anneal.”
There are two major steps involved in the manufacturing of galvannealing steel. These include:
The first step is to clean the contaminants from the metal surface of the steel. After which, you must dip it in a molten zinc bath at around 450ºC. The molten zinc reacts with the steel’s surface, producing a zinc-alloy layer that needs anneal at a high temperature to foster the diffusion of the iron and zinc atoms. This process usually provides a coating that bonds firmly to the steel’s surface, creating excellent corrosion resistance.
This technique is similar to hot-dip galvannealing, but you should consistently perform it on the production line. After cleaning the steel, then you can pass the steel through a series of zinc baths and annealing furnaces to produce a continuous coating. More so, manufacturers often use this method for high-volume manufacturing of galvanneal steel parts.
Advantages of Galvanneal Steel
Excellent Paint Adhesion
This steel has a polished and uniform surface that is suitable for painting. The zinc-iron alloy layer offers an excellent base for paint adhesion. As a result, the applied paint bonds firmly to the galvanneal still with fewer chances of flaking or peeling.
Galvanneal steel is highly malleable and can be bent or formed into different complex shapes without damage. Therefore, it is a perfect material for applications that involves considerable forming and bending.
Smooth, Matte Finish
Galvanneal steel possesses an even, non-spangled surface with a smooth, matte finish. This steel offers a non-reflective finish required in specific applications.
Disadvantages of Galvanneal Steel
Lower Corrosion Resistance
Although galvanneal steel offers excellent corrosion resistance, its zinc-alloy layer is thinner than the traditional galvanized steel’s pure zinc coating. As a result, galvanneal steel may not resist corrosion in a harsh environment like galvanized steel would.
Galvanneal steel is more expensive than galvanized steel because of the additional production processes involved in creating the zinc-iron alloy layer.
Vulnerable to High Temperature
Galvanneal products don’t perform well under high temperatures because the zinc-iron alloy layer becomes vulnerable to deformation above 200ºC.
Overview of Galvanized Steel
Galvanized steel is a sheet metal type usually coated with a zinc layer to ensure its corrosion resistance. Hence, the term “galvanizing” refers to the process of coating this metal sheet. The processes involved include:
Galvanizing steel through the hot-dip process is the most standard galvanizing method. You must submerge the steel sheet in a molten zinc solution at about 450ºC, in which the zinc reacts with the steel, creating a zinc-iron alloy layer on the sheet metal’s surface. This coating improves the metal sheet’s physical properties, enhancing its corrosion resistance.
Electro-galvanizing is another famous method of galvanizing. This process requires using electric current to apply zinc coating to the sheet metal. Firstly, you must clean and pass the sheet metal through a solution filled with zinc ions. Then, you need to apply an electric current to the solution allowing the zinc ions to glue to the steel sheet. This process is best used for thinner sheets and creates a thinner zinc coating in contrast to hot-dip galvanizing.
Advantages of Galvanized Steel
The followings are the benefits and drawbacks of galvanized metal you need to keep in mind:
Galvanized steel is highly durable and can withstand corrosion for a longer time. So, it is a reliable material with a long life expectancy.
Products made with hot-dip galvanized steel often require less maintenance throughout their lifetime. Hence, it is an inexpensive material for many applications.
This sheet metal is commonly used for various applications due to its cost-effectiveness.
Disadvantages of Galvanized Steel
Limited Color Options
Galvanized steel has restricted color options as it usually has a gray or silver appearance which is not ideal for some designs with specific color demands.
Galvanized sheet metal often has thicker coatings which impact its weldability, hindering the use of the sheet metal in specific applications.
Unsuitable for High-temperature Applications
This steel is incompatible with high-temperature applications because the zinc coating can disintegrate and release harmful fumes.
Comparison Between Galvanized vs. Galvannealed Steel
Although galvanized and galvannealed steels have some similarities, there are key differences that can help determine the best material for your product between these steel types.
1. Manufacturing Process
Galvanized steel is created through the immersion of steel into a molten bath of zinc at precisely 450º Celsius. The zinc layer acts as a shield between the environment and the steel, preventing the steel from corrosion.
The process of producing galvannealed steel is similar to that of galvanized steel because you must first immerse the steel in the molten zinc solution. Then, you heat the steel in an annealing furnace to a higher temperature of about 1050ºF to anneal the steel. The underlying iron element melts to the surface, creating a mixture of zinc and iron coating. The process produces a zinc-iron alloy coating that attaches to the steel, enhancing its durability and resistance to corrosion.
A pure layer of zinc, usually thin and with a polished appearance, covers the galvanized steel. However, it may possess a tiny portion of iron, a constituent of stainless steel. You can measure this coating an ounce per square foot, often ranging from 0.30 oz/ft² (G30) to 2.35 oz/ft² (G235).
Meanwhile, product manufacturers often coat galvanneal steel with zinc-iron alloy, which has a matte finish. It has an excellent coating comprising three layers (gamma, delta, and zeta). You can measure its coating in thickness, ranging from 0.40 oz/ft² (A40) to 0.60 oz/ft² (A60). Furthermore, manufacturers anneal galvannealed steel after coating.
Galvanized steel has a polished and spangled look. It offers improved strength and resistance to corrosion, making it suitable for outdoor applications. However, this sheet metal material is quite soft, which makes it vulnerable to scratching.
Properties of Galvanized Steel
Galvanized steel has high corrosion resistance, making it the perfect material for outdoor applications. Its zinc coating protects it from moisture and other corrosive compounds, protecting the concealed steel from rusting.
This metal sheet is durable and highly durable, making it suitable for applications like manufacturing and construction. The zinc coating strengthens the steel, giving it additional rigidity and strength required in most applications.
The galvanized sheet material is highly ductile. As a result, you can easily bend or form that sheet without damaging it. More importantly, its flexibility makes it a reliable material for making different parts in different industries.
You can utilize various welding methods such as TIG, MIG, and stick welding to weld galvanized steel into different shapes. However, it would help to note that zinc coating releases toxin fumes when exposed to heat. So, it is advisable to take safety precautions when welding galvanized sheets.
In contrast, galvannealed steel offer excellent formability and better paint adhesion. Its surface is typically smoother, and its matte finish makes it more durable. Hence, manufacturers often use galvanneal steel in applications that need more excellent abrasion resistance.
Properties of Galvannealed Steel
The Galvanneal steel allows painting due to its smooth and even surface. The zinc-iron alloy coating gives an impeccable base for paint adhesion. So, the paint applied is less susceptible to flaking and peeling over time. As a result, galvanneal steel is a popular option for making automotive body panels and other parts with high-quality paint and alodine finish requirements.
You can form galvanneal steel into different complex shapes without damaging it due to its ductility. This attribute is critical in applications that involve subjecting the steel to considerable bending, including the construction of HVAC ductwork or automotive parts.
Lower Coating Thickness
Galvanneal steel has a thinner zinc-iron alloy layer providing equal resistance to corrosion as galvanized steel, only with a lesser weight and thickness. Reduced coating thickness is critical in applications such as the construction of vehicles and aircraft where weight and space are a priority.
This sheet metal has a matte appearance with low reflectivity than galvanized steel. This is due to the zinc-iron alloy layer on the galvanneal steel, which ensures the surface is non-spangled and uniform. This quality is crucial in applications like signage and building construction with high demand for a non-reflective finish.
Galvanized steel has a shiny, spangled surface due to the crystallization of the zinc coating during the galvanizing process. The surface is usually smooth and homogeneous, with a bright silver color that can range from matte gray to glossy reflecting. The thickness of the zinc coating can also have an impact on the aesthetic, with heavier coatings frequently resulting in a more noticeable spangle pattern.
On the other hand, galvannealed steel has a dull, matte gray appearance due to the annealing process that follows the galvanizing process. The zinc coating is allowed to react with the iron in the steel substrate during annealing, generating a layer of iron-zinc alloy. This alloy layer is responsible for the characteristic appearance of galvannealed steel.
Applications of Galvanized Steel
Manufacturers across industries often use galvanized steel in outdoor and corrosive environments. Here are some of the typical applications of this steel.
HVAC Systems: HAVC (heating, ventilation, and air conditioning) systems manufacturers often use galvanized steel. It is affordable, resistant to corrosion, and durable. Hence, it is a better choice for this application. HVAC systems often require ductwork to spread air throughout a building; galvanized steel is the perfect metal sheet.
Agriculture: Galvanized steel is one of the ideal sheet metals for making agricultural equipment since it is not susceptible to corrosion and rust. Most tools in this sector are usually exposed to external environments, and galvanized products can withstand any environment for an extended period.
Industrial Applications: Manufacturers commonly employ galvanized steel in industrial applications, including the production of storage tanks, pipes, and other crucial equipment for oil and gas extraction.
Applications of Galvannealed Steel
On the other hand, you will find galvanneal steel commonly used for indoor applications requiring better paint adhesion and formability. Some of these applications include the following:
Automotive Industry: Automobile manufacturers commonly use galvanneal steel to create chassis components, body panels, and other structural components. It offers excellent formability and resistance to corrosion and easy paintability for a quality finish.
Appliance Manufacturing: Galvanneal steel is widely used to produce various appliances, including washing machines, refrigerators, dryers, ovens, cookers, etc. It offers excellent formability and resistance to corrosion, making it a perfect choice for producing appliance parts like frames, panels, and other structural components.
Electrical Systems: Galvanneal steel is an ideal choice for making junction boxes, conduits, and enclosures due to its formability and resistance to corrosion. In addition, the paintability of this sheet metal allows the customization of components, ensuring it blends with the surrounding environment.
Generally, galvannealed steel costs more than galvanized steel because it requires an additional manufacturing process. More importantly, the cost typically varies based on the thickness of the coating and the order’s size.
Galvanneal vs. galvanized steel is a versatile sheet metal type suitable for various applications. Each steel type has distinctive attributes, making neither galvanized nor galvanneal steel the best choice for all applications. Thus, the ideal choice between these two depends on your products’ specific requirements.
WayKen is your best partner if you need professionals to help determine the ideal steel type for your project. With extensive expertise in the field of machining, our team of professionals is well-equipped to assist you in machining metal parts, whether it be galvanneal or galvanized steel.