We treat galvanizing of steel as one of the most reliable methods of anti-corrosion protection, especially where structures operate in diverse and demanding environmental conditions. In our work, we rely on metallurgical and electrochemical phenomena, because this combination allows you to create a coating that not only isolates the steel from the environment, but also actively protects it through anodic protection. This coating remains stable for many years, and we can precisely control its properties at every stage of the process. We know from experience that galvanizing technology plays a crucial role in construction, energy, transportation, and industry, as it determines whether a structure will maintain its performance for several seasons or even decades.
What is steel galvanizing and why does the zinc coating protect against corrosion so effectively?
When working with zinc coatings we always rely on electrochemical potential difference between zinc and iron. Zinc plays a role galvanic anode, and the steel acts as a cathode, which means that the zinc takes over the corrosion process. This arrangement guarantees protection even if the coating is locally damaged, because the mechanism galvanic cathodic protection remains active. This property makes galvanizing steel one of the most effective protective technologies.
During use, we observe how the surface of the zinc coating gradually becomes covered with a layer oxides, hydroxides and basic zinc carbonates. This patina creates a stable, tightly adherent protective layer that further limits oxygen and moisture from reaching the metal. This arrangement significantly slows down the rate of coating deterioration, especially in temperate environments, where the patina develops evenly and remains durable over time.
Hot-dip galvanizing – process, coating properties and the importance of Fe-Zn metallurgy
Hot-dip galvanizing involves immersing steel elements in liquid zinc at a temperature of approximately 450°C. Under such conditions, zinc reacts with steel and creates metallurgical Fe-Zn alloy layers. The coating structure consists of gamma, delta, zeta, and eta layers, each responsible for a different material property. The innermost layers are characterized by high hardness and mechanical resistance, while the outer layer of pure zinc provides electrochemical protection.
The zinc coating created in the hot-dip process is an integral part of the component, not just an applied layer. Its durability depends on the bath temperature, immersion time, and chemical composition of steel, especially the silicon and phosphorus content. It is the appropriate analysis of the steel grade that allows us to predict the rate of growth of Fe-Zn layers and avoid undesirable Sandelin effect (a phenomenon in which steel with a certain silicon content overreacts and forms a thick, dull, and more brittle coating.) A well-executed hot-dip galvanizing process provides a coating with excellent resistance to weathering and mechanical conditions, making this method indispensable for large steel structures.
Galvanic zinc plating – a precise zinc coating created by electrolytic method
Galvanic zinc plating is carried out in an electrolyte solution in which the workpiece works as cathode, and zinc is deposited on its surface in stable, controlled conditions. The process takes place in room temperature, which allows us to precisely control the thickness and structure of the coating and adapt it to the requirements of high-precision components.
In practice, most depends on current density, which shapes the size of zinc crystallites and influences the uniformity of the surface. Baths alkaline they work well with elements with complex geometry, while acid baths allow you to obtain a fine-crystalline, aesthetic coating with increased resistance to white corrosion. The final stage is passivation, which stabilizes the freshly deposited zinc and increases the operational resistance of the coating. In our work, we use passivation chrome-free based on titanium and zirconium compounds, because they ensure the durability of the layer and at the same time are safe for the environment.
Why galvanizing steel ensures such long durability in practical applications
The zinc coating wears evenly and predictably. Under standard conditions, its degradation rate is typically 1-2 μm per year, therefore a coating several dozen micrometers thick can work for several dozen years without additional intervention. The predictability of the wear process is one of the reasons why galvanizing steel is considered the most cost-effective technology in corrosion protection. duplex, i.e. a combination of galvanizing and painting, durability increases even more because the paint limits the access of oxygen, and the steel remains protected by the zinc layer even in the event of micro-damage to the paint coating.
When assessing the durability of security, we always refer to classes of corrosive environments compliant with the standard PN-EN ISO 12944. In environments C1-C2, typical of dry or slightly damp interiors, the zinc coating wears very slowly and can provide protection for up to several decades. C3-C4, characteristic of urban and industrial areas, a stable degradation rate allows for long-term protection with an appropriate coating thickness. In environments C5 / CX, where structures are exposed to salt mist, high humidity or aggressive industrial gases, galvanizing still proves to be an effective protection, but requires a thicker coating or the use of a duplex system, which can extend the life of the structure even several times.
Technical facts about galvanizing
- Fe-Zn layers in hot-dip galvanizing reach hardness of up to 300 HV, therefore the coating effectively protects the steel not only against corrosion, but also against mechanical damage that standard paint coatings cannot prevent.
- In galvanic processes we react to any change in current density, because even the slightest deviation can change the structure of the deposit and its resistance to white corrosion. For this reason, we constantly monitor bath parameters and conduct regular laboratory analyses.
- Zinc has the ability to locally migrate ions, which helps limit the development of corrosion at micro-damages. This property is particularly noticeable in situations where the paint coating ceases to protect the steel immediately after the continuity is broken.
- In environments with increased CO₂ content, zinc patina forms faster and is more uniform., which improves the long-term stability of the coating. In urban areas, we can clearly see that this phenomenon reduces the rate of coating wear.
- During hot dip galvanizing, we control the cooling method of the element, because the rate of heat release influences the formation of microcracks in the outer layers of the coating. Proper temperature control directly translates into the durability and flexibility of the Fe-Zn layer.
- In electroplating we observe the phenomenon of current shading, in which the current reaches the edges more intensely than the recesses. Therefore, when setting the parameters, we ensure that the deposit is formed evenly across the entire part and does not cause differences in coating thickness.
Galvanizing in Strumet
At Strumet, we treat steel galvanizing as an essential element of our overall structural protection technology. surface preparation, stable bath parameters and appropriate process conditions, because they determine the quality and durability of the zinc coating. We analyze the steel composition and select the immersion time and method to ensure the coating develops evenly and maintains its properties over time.
This process allows us to obtain coatings that are resistant, homogeneous and predictable in use. If you require galvanizing performed under controlled conditions and with full responsibility for the result, we will prepare the elements to meet your requirements.
