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.

Galvannealed steel has a flat gray, slightly-matted finish. The surface is attractive. That's a result of the annealing process, and it's easy to paint because the zinc coating is more absorbent. It is often chosen for architectural applications and also in the auto industry.

After going through the hot-dip process, the carbon steel goes through a secondary process to create a galvannealed coating. The zinc-coated steel is heated to a higher temperature, pulling the iron from the steel and causing it to mix with the zinc coating and create a zinc-iron alloy coating. The added iron is what makes the galvannealed metal have different properties than galvanized metal. It also contributes to a different appearance; galvannealed metal has a more consistent, matte finish made of 90% zinc and 10% iron. However, the presence of iron in the coating can cause it to have a red tint, but it does not mean that the steel is rusting. Galvannealed coatings are designated with an "A".