Galvanizing is one of the widely used methods for protecting metals from corrosion. It involves applying a thin zinc coating to a thicker base metal like iron metal. The process helps to shield the metal from the surrounding environment. When a metal undergoes galvanization, it does not experience any corrosion. However, without the zinc coating, the metal remains exposed to the elements and potentially oxidizes and corrodes faster. There are several ways of galvanizing metals, including hot-dipped galvanization and pre-galvanizing.
Hot-Dipped Galvanization vs. Pre-Galvanizing: What Are They?
As the name suggests, in hot-dipped galvanization, experts dip the steel in hot, molten zinc. When the zinc coats the steel, a metallurgical reaction occurs between the iron component of the steel and the hot zinc. The reaction known as the diffusion process occurs when the coating collects perpendicular to every surface, creating a uniform thickness.
When the expert removes the steel from the zinc bath, it reacts with the oxygen in the air to form zinc oxide. It then reacts with carbon dioxide and forms the final protective coating of zinc carbonate. With multi-layered zinc coating and iron-zinc alloy, the steel becomes corrosion-resistant.
Pre-galvanizing, also called mill galvanizing, is another galvanizing process close to ho-dipped galvanizing. However, this process occurs at the very first stage of production. The process takes place at steel mills that have a specific shape. Pre-galvanizing involves a few steps of hot-dip galvanizing, like cleaning the surface, hot zinc bathing, and recoiling.
Key Differences Between Hot-Dipped Galvanizing and Pre-Galvanizing
Hot-dipped galvanization is an economical choice that you can execute on simple and complex shapes. Experts use it on objects fabricated beforehand and yet not galvanized. The hot-dipped galvanization plays the last step.
On the other hand, a metal requires undergoing pre-galvanizing at the first production stage. It mainly occurs at the mill and later undergoes cutting into size and fabrication.
Since the galvanizing process involves the application of a protective coating for the steel and metals, it is essential to consider the coating finish of the two methods of manufacturing galvanized steel.
Although both methods result in uniform thickness, the hot-dipped galvanization produces a thicker layer of protection than the other method.
Hot-dipped galvanizing requires dipping the entire steel and other metals into the molten vat of zinc. The galvanized steel comes with a continuous coating over the surface. On the other hand, pre-galvanizing requires performing before cutting the sheets into perfect sizes and pieces; therefore, the cut edges do not undergo any coating.
Since the process of pre-galvanizing undergoes at the mills, any coating applied after cutting the metals does not damage the layer. On the other hand, coating formability applied on hot-dipped galvanized steel is not advisable, as it might damage the protective coating of the products.
The hot-dipped galvanization forms a bright finish for the galvanized steel, which might or might not be uniform. On the other hand, the pre-galvanizing process produces a uniform bright finish for the coating.
There are numerous differences between hot-dipped and pre-galvanizing processes. Understanding the differences helps in choosing suitable methods and products for different projects.