Galvanization is a process of applying zinc coating to a steel product, which protects the material from rust and decay. Bare metal is submerged into hot pool of molten zinc (usually 98% of zinc by weight), which “sticks” to the surface through chemical reaction. We are simplifying the process here, but in reality it contains multiple steps and various material preparations. Also the zinc bath can contain other trace materials like aluminum, nickel and tin to enhance the appearance of the finished product.
The thickness of the zinc coat can be specified by the client and should be tested and verified after the galvanization (check Standard Specification for Zinc (Hot-Dip Galvanizing) Coatings on Iron and Steel Products A123/A123M
). You can identify zinc coated products by the characteristic spangle in gray color.
What is the role of the zinc?
Zinc acts as a physical barrier and a sacrificial anode and is depleted over time. It prolongs the life of the steel to some extent, even if some small scratching and other physical damage occurs. This is the result of a chemical reaction we’ll discuss next. Because the zinc (Zn) is more electrochemically active than iron (Fe), the electrons flow from zinc to iron, which turns the zinc atoms to positively charged ions (Zn2+). Those then react with negatively charged hydroxyl ions (OH–) to form Zn(OH)2. After time, the patina forms which further protects the steel.