We have talked a lot about galvanized steel versus other metals, but not galvannealed. Often, people seem to confuse them because of the similar sounding names, and they are very similar… but also different. Let’s look at both galvanized and galvannealed steel to see how they stack up against each other.
Similarities of the Two
Both galvanized and galvannealed steel are coated at the mill or plant and are designed for resistance against rust and corrosion. They fall under the ASTM A 653/A 653M category and they both have the same weight of coating. Finally, the beginning of the production process is the same with both types of steel going through the hot-dip process.
As mentioned above, galvanized steel is passed through the hot-dip process and receives many unique benefits. The visual appearance is a shiny speckled surface that is characterized by dark and light gray patches. The size and shape of the pattern can be controlled by these three things:
- Zinc alloy
- Bath temperature
- Cooling rates
The coating on galvanized steel is also more thick than galvannealed.
Galvannealed steel goes through an extra step in the process. Once the steel is coated in zinc, it then gets heated to a higher temperature than galvanized steel (over 1000° F). During this process, the iron gets pulled from the steel which causes it to mix with the zinc. The coating becomes harder, more scratch-resistant, and more uniform visually.
Unlike galvanized steel, galvannealed steel does not have a speckled appearance. The finish of galvannealed steel is more of a flat gray with a matte texture to it. For painting and welding purposes, galvannealed steel bonds better.
If you have an exterior design project, or in a damp/salty environment, you will want to consider using a stronger coating like G90. If it is more likely to be scratched or impacted, then the harder A40 galvannealed finish is preferable.
As for considerations with appearance, galvanized steel can be painted, finished, or coated. Although, the natural aesthetic of the steel is quite appealing to many designers. Speckle-patterns are very unique to galvanization and can ensure that no pieces will be the same.
The appearance of galvannealed steel has a slight matte texture. It is good for painting because the paint bonds well with this type of surfacing. If you prefer a flat painted coat, galvannealed steel may be more appropriate.