Galvanized steel is a material that, in practice, determines the durability of the entire structure. We're not talking about a thin decorative coating, but rather a protective technology that modifies the steel's behavior in environments with moisture, fluctuating temperatures, and industrial pollutants. In the case of hot-dip galvanizing, zinc not only coats the surface but also reacts with iron, creating alloy layers. Fe–Zn permanently bonded to the substrate.

Steel corrosion is an electrochemical process that begins immediately upon contact with water and oxygen. In construction, energy, and industrial structures, this translates into reduced load-bearing capacity, aesthetic degradation, and rising maintenance costs. A properly applied zinc coating interrupts this process at the material level, separating the steel from the environment while simultaneously absorbing corrosive reactions at potential damage sites.

With the appropriate coating thickness and taking into account the environmental corrosion class, galvanized steel can operate for 30, 40, or even more than 50 years without the need for renovation. Therefore, in modern construction and industry, it is not a technological addition, but a design standard that influences the entire life cycle of a structure.

What is the steel galvanizing process?

At Strumet, we conduct galvanizing as a conscious technological step in which we protect the steel with a layer of zinc, to effectively protect it from corrosion in atmospheric and industrial environments. We don't treat this as a simple metal coating, but rather as a process that directly impacts the durability, safety, and operating costs of the entire structure.

Depending on the purpose of the element and its operating conditions, we use two main technologies:

• hot-dip galvanizing,
• electrolytic galvanizing.

In the case of hot dip galvanizing, we immerse the steel in liquid zinc, which leads to the formation of alloy layers permanently bonded to the substrate. This creates a thick, resistant coating designed for structures operating in demanding environments.

During electrolytic galvanizing, we deposit zinc from the solution using an electric current, which results in a thinner, very even coating, which does not significantly affect the dimensional tolerances of the element.

Each of these methods gives a different effect in terms of coating thickness, structure and corrosion resistance, therefore we always select the technology based on the function that the element is to perform in real working conditions.

Hot-dip galvanizing – durable protection for large structures 

In hot dip galvanizing, we immerse the steel in a zinc bath at a temperature 445-455°C. At this temperature, intense diffusion occurs between iron and zinc. The zinc doesn't just remain on the surface—the atoms penetrate the steel structure, creating Fe-Zn alloy layers of varying hardness and composition.

A typical coating structure consists of several layers:

• alloy layers at the base, very hard and abrasion-resistant,
• an outer layer of pure zinc, more plastic, responsible for anodic protection.

The coating thickness in hot-dip galvanizing is most often in the range of 70–150 µm, in accordance with the requirements of the PN-EN ISO 1461 standard. In the case of steel with a specific chemical composition or a greater element thickness, the coating may be even thicker.

The advantage of this method is that the zinc reaches all surfaces of the element – including the interior of closed profiles, technological spaces, and openings. Protection covers the entire cross-section of the structure, not just the visible parts.

We use hot-dip galvanizing for:

• structures of industrial halls,
• bridges and viaducts,
• power poles,
• support systems for industrial installations,
• elements of road and railway infrastructure.

Electrolytic galvanizing – precision for smaller components 

In electrolytic galvanizing, zinc is deposited from an electrolyte solution using an electric current. The steel component acts as a cathode, and zinc ions are reduced directly on its surface, creating a compact and controlled layer. The process is performed at temperatures significantly lower than in hot-dip galvanizing, which maintains the component's dimensional stability. The coating thickness is most often in the range of 5–25 µm, and its uniformity means that it does not disturb assembly tolerances or thread geometry.

Electrolytic galvanizing is used primarily for:

• screws and nuts,
• small structural elements,
• technical components where surface aesthetics and precision of workmanship are important.

In moderately aggressive environments, this coating effectively protects steel against corrosion and at the same time allows us to maintain dimensional accuracy of the detail and stability of its technical parameters, which is important for assembly elements and components working in precise systems.

Why galvanized steel is corrosion resistant

Resistance galvanized steel It is based on two mechanisms that work simultaneously and complement each other, so that the protection is not limited to the surface separation of the metal from the environment.

The first one is physical barrier, because the continuous zinc layer effectively isolates the steel from moisture, oxygen and industrial pollutants, thus limiting the possibility of initiating corrosive reactions. The second mechanism is cathodic protection, resulting from the fact that zinc has a lower electrochemical potential than iron, therefore in the event of damage to the coating, zinc reacts first and takes over the oxidation process.

Consequently, even a local scratch does not lead to the immediate development of steel corrosion, because zinc corrosion products, mainly oxides and carbonates, gradually fill the resulting gap, limiting further access of moisture and oxygen to the substrate, which significantly extends the durability of the entire structural element.

Does galvanized steel rust and how long does it last?

A freshly galvanized surface has a bright, metallic sheen. Depending on the steel composition and process conditions, it may be more gray and dull. Upon exposure to air, the coating gradually dulls. A stable protective layer composed of zinc oxides and carbonates forms on its surface. This color change does not indicate a deterioration in quality, but rather a natural stage in the coating's maturation.

The rate of zinc depletion depends on the environmental corrosivity class. According to PN-EN ISO 12944, classes C1 to C5 are distinguished. In a moderate environment, zinc depletion can be approximately 1–2 µm per year. This means that a 100 µm thick coating can last for several decades.

In industrial or marine environments, the rate of wear is higher, but a properly selected coating thickness still allows for long-term durability. It is this predictable degradation, involving the gradual depletion of zinc, that makes galvanized steel a long-term solution.

The use of galvanized steel in various industries

We use galvanized steel in many industries where structures must operate stably for years:

• structural and infrastructure construction,
• energy industry,
• automotive,
• agriculture,
• machinery industry,
• telecommunications systems.

In each of these industries, components are exposed to moisture, temperature fluctuations, salinity, or industrial pollution. The zinc layer creates a protective barrier and simultaneously acts electrochemically, so galvanized steel maintains durability even in environments with increased corrosiveness.

How to care for galvanized steel so it lasts for decades

Galvanized steel does not require complicated maintenance, but its durability depends on regular inspection and careful use. In practice, periodic surface inspection and removal of residual contaminants such as road salt, industrial sediments, or mud, which can accelerate the wear of the zinc layer, are sufficient. Cleaning should be carried out using water and mild, pH-neutral cleaning agents, avoiding aggressive chemicals and hard abrasive tools. In highly corrosive environments, it is worth considering a system. duplex, where the paint provides an additional barrier and the zinc coating still provides electrochemical protection.

At Strumet, we emphasize that the quality of the galvanizing itself and the appropriate coating thickness are crucial, as they largely determine whether the structure will operate without problems for decades.