What is electrolytic galvanizing?

Electrolytic galvanizing is a process of depositing zinc on metal objects through the application of electric current. This takes place in a galvanic cell, where zinc is reduced at the negative pole (cathode), and the amount of zinc deposited is proportional to the through current. The process takes place at temperatures of 20-25°C, and is known as “cold galvanizing” to distinguish it from hot dip galvanizing, which operates at temperatures around 450°C.

Galvanizing is widely used on ferrous materials to take advantage of the cathodic/sacrificial protection effect of zinc. In corrosive environments, zinc corrodes first, acting as a sacrificial layer and preventing corrosion of the underlying iron.

The process involves current flowing through the electrolytic cell, migrating zinc ions to the material to be galvanized along the flow lines of the electrolytic field. This results in varying deposition thickness, with areas of shorter path and peaks showing higher thicknesses.

To preserve the aesthetic appearance and improve the corrosion durability of electrodeposited zinc, treatments such as passivation and sealing are performed. Passivation creates a stable layer of zinc salts that contains other elements such as chromium, cobalt, and silicon, providing stability against corrosive agents. Sealing, on the other hand, consists of an organic film that chemically bonds to the passivation, adding additional protection.

During the galvanizing process, an undesirable reaction of hydrogen formation occurs. To prevent stress due to hydrogen absorption by the ferrous material, especially in materials with high tensile strength, it is necessary to carry out “dehydrogenation” immediately after galvanizing. This step prevents breakage of components in operation and before use.