What is the difference between Galvanized and Galvannealed?
Both these are the methods used to coat the metal in order to save it from rust and corrosion.
Galvanization is the process in which a protective coating of zinc is applied to iron or steel to prevent corrosion and rust. It is done using two methods hot-dip and thermal diffusion. To prevent steel from rusting either it is coated with a protective layer or its form is changed. Changing the form is costly so galvanization is preferred as a cost-effective alternative. When iron or steel is galvanized, it becomes durable, corrosion and rust-resistant. The most common method used for galvanizing is the hot-dip method.
Galvanized Steel remains corrosion-resistant for up to 30 years. It does not lose its strength or characteristics after being galvanized; in fact, it makes it corrosion resistant and durable. It is great for welding, good for cutting, machining, and fabricating. Galvanized Steel angle is used for different applications due to its following characteristics:
- Corrosion Resistant
- Easy to cut and weld
- Good Strength
- Ease of fabrication
It is quite similar to galvanizing because in this too iron or steel is coated with zinc in order to protect it from rust and corrosion. It does not change or have any effect on the properties of the metals. Galvanneal involves three steps, first, it is galvanizing and then the second step requires the metal has to undergo a low-pressure air knife that is supposed to blow away the excessive coating prior to solidifying. It will leave a thin coating on the metal. Then in the third step, it is kept in the furnace for annealing and this complete process is called galvannealed. The galvannealed metal has the following characteristics:
- Can be painted
- Hard coating
Comparison Between Galvanization and Galvannealing:
Both these methods involve dipping the metal in molten zinc to create a layer in order to provide protection to the metal against rust and corrosion. Galvannealing process involves additional step of annealing which involves heating the metal after galvanization. It provides better formability and paint application surface improvement.
After galvanizing or galvannealed the metal is exposed to the environment resulting in zinc and oxygen reaction forming zinc oxide. When zinc reacts with water it forms zinc hydroxide. Both these form a layer over the metal that protects it from rust and corrosion making is durable.
Appearance and Surface
Galvanized metal surface has a marble-type pattern in light and dark grey color which is called spangling. Each piece of galvanized metal has a different look; however, it is a more affordable option.
On the other hand, galvanealed metal has a matte finish in one color i-e grey, and a smooth surface. The annealing process improves the surface and makes it suitable for painting. Better appearance is the reason why galvannealed metal is used for architectural applications readily despite its higher cost.
No matter what choice you make regarding galvanization or galvannealing, both these provide good corrosion resistance, durability, and a unique appearance. For industrial applications where appearance is not the main concern but cost-saving the use of galvanized metal is recommended.