In humid air, outdoors in the wind and rain, and even in special environments containing corrosive substances,
ordinary steel products often find it difficult to resist the onslaught of rust and corrosion. However, there is a
centuries-old process, can give the steel a strong “armor”, so that its service life exponentially longer - this is
galvanized. It is not only the most economical and effective means of steel corrosion, but also the modern
industry and construction of indispensable basic protection technology.
Zinc shield body protection: principle and mission
The core of galvanizing is the use of zinc, an active metal, to protect the steel substrate. Its anti-corrosion
mechanism is based on two main principles:
Physical barrier effect: uniform coverage of the zinc layer on the surface of steel, as a dense physical barrier,
he steel substrate and the external moisture, oxygen and other corrosive media isolated.
Electrochemical Protection (Sacrificial Anode): This is the most unique and long-lasting protection mechanism for
galvanizing. In an electrolyte environment (e.g., humid air), the standard electrode potential of zinc is more negative
(more reactive) than iron. When the plating is scratched or broken, exposing the steel inside, the zinc corrodes
preferentially (sacrifices itself) and continues to supply electrons to the steel substrate, thus effectively stopping the
steel from rusting. Even with localized damage to the zinc layer, this protective effect does not stop as long as there
is still zinc present in the surrounding area.
The mission of galvanizing is clear and critical: to significantly extend the service life of steel products, reduce
maintenance costs, guarantee structural safety and save resources.
Process genres: hot-dip and electro-galvanizing
According to the principle of the process and the final form, galvanizing is divided into two main mainstream technologies:
Hot dip galvanizing:
Thick coating: Usually above 70-100 microns, even up to 200 microns, providing a long corrosion protection life (20-50 years
or more under standard atmospheric conditions).
Strong adhesion: Metallurgically bonded alloy layers provide an exceptionally strong bond between the coating and the substrate.
Good Coverage: Provides complete coverage of internal and external surfaces and crevices of the workpiece.
Appearance: A characteristic silver-white or slightly grayish “zinc bloom” surface is formed (the size of the bloom can be varied
or a smooth surface can be obtained by controlling the composition of the zinc solution and the cooling method).
Process: This is the classic and most widely used method. The steel workpiece, which has undergone a rigorous pre-treatment
(pickling and descaling, auxiliary plating), is immersed in a molten zinc solution (about 450°C). A metallurgical reaction occurs
at the interface between iron and zinc, resulting in a series of alloy layers with different zinc-iron ratios (from the inside out:
Γ-phase, δ1-phase, ζ-phase), with a pure zinc layer in the outermost layer.
Characteristics:
Applications: Preferred for structural components exposed to harsh outdoor environments for long periods of time, such as
electric power pylons, highway guardrails, building steel structures, transmission and transformation brackets, bridge
components, pipelines, and large fasteners.
Electro-galvanized:
Thin and uniform plating: generally around 5-25 microns, with delicate, smooth and bright appearance and various colors.
High dimensional accuracy: minimal impact on workpiece dimensions, suitable for precision parts.
High production efficiency: easy to realize automatic continuous production.
Relatively low corrosion resistance: limited thickness, not as long as hot-dip zinc in harsh environments, but passivation
film can significantly improve its protective ability.
Process: In an electrolytic solution containing zinc ions, the workpiece to be plated is energized with direct current as the
cathode. The zinc ions gain electrons on the surface of the cathode (workpiece), are reduced to zinc metal atoms and
deposited on the surface of the steel to form the coating. This is usually followed by passivation (chromate or environmentally
friendly chrome-free passivation) to form a colored (blue-white, multicolored, black, etc.) or white protective film to
further improve corrosion resistance and aesthetics.
Features:
Applications: automotive parts (body, chassis parts), electronic and electrical shells, daily-use hardware (screws, nuts, tools),
home appliances accessories, construction hardware and other parts of the size accuracy, appearance requirements, and
the working environment is relatively mild.
galvanized layer of “vitality”: the key to corrosion resistance
The protective effect of the galvanized layer is not static, and its “vitality” is affected by multiple factors:
Thickness of the zinc layer: This is the primary factor in determining the life of the protection. The thicker the coating, the
longer the consumption time and the longer the protection. This is where the advantages of hot-dip galvanizing come into play.
Environment: The more corrosive the environment (e.g. industrial atmospheres, marine environments, high humidity, acid rain,
exposure to chemicals, etc.), the faster the zinc layer is consumed. The advantages of hot-dip zinc are more obvious in harsh
environments.
Passivation film quality (electro galvanized zinc): A good passivation film effectively retards corrosion of the zinc layer and
the generation of white rust (corrosion products of zinc).
Zinc layer composition and structure (hot-dip zinc): The proportion and density of the alloy layer affects corrosion
resistance and adhesion.
Beyond rust prevention: the multidimensional value of galvanizing
Galvanizing is much more than rust prevention:
Economy: Although the initial cost may be higher than for coatings such as paint, its long maintenance-free life significantly
reduces maintenance and replacement costs throughout its life cycle, making it an excellent choice for long-term return
on investment.
Reliability: The coating is metallurgically bonded to the substrate (hot-dip zinc) or physically bonded (electro-galvanized +
passivated) and does not flake off easily, resulting in stable and reliable protection.
Versatility: From giant steel structures to miniature screws, from land to sea, galvanizing offers effective protection solutions.
Environmentally friendly (relatively): Extending the life of a product is in itself the most environmentally friendly thing you can do.
Zinc is a naturally abundant element and the energy consumption of the hot dip galvanizing process is relatively centralized and
controlled. The environmental friendliness of zinc electroplating is mainly reflected in the promotion of chromium-free
passivation technology and advances in wastewater treatment technology. The zinc itself can be recycled.
Aesthetics (especially for zinc plating): A wide range of color options are available to meet decorative needs.
Challenges and Evolution: Greener, Smarter, More Efficient
Galvanizing technology is also evolving to meet new challenges:
Environmental upgrading: In the field of zinc electroplating, chromium-free and low-toxicity passivation technologies (e.g.
trivalent chromium passivation, silane passivation, zirconium-titanium passivation, etc.) are accelerating the replacement of
traditional hexavalent chromium passivation. Hot-dip zinc is also optimizing the formulation of plating aids to reduce emissions.
Performance Improvement: Development of highly corrosion-resistant alloy coatings (e.g., zinc-aluminum-magnesium) that provide
far greater protection than traditional galvanizing at the same thickness; and development of thinner, higher-performance
electroplated zinc coatings.
Intelligence and automation: online monitoring and control, robotics applications, etc. to improve process stability and productivity.
Application Expansion: Explore in-depth applications in new energy sources (e.g., photovoltaic mounts, wind turbine towers),
ocean engineering, and other emerging fields.
Conclusion
Galvanizing, which seems to be a traditional surface treatment process, is actually one of the solid foundations of
modern industrial civilization. It for the steel to wear this layer of “zinc” clothing, not only to resist the erosion of the
years, but also to guard the reliable operation of countless bridges, buildings, vehicles, equipment. From the rough
and tough hot-dip zinc to the delicate and varied electric zinc plating, different processes provide optimal solutions
for different needs. As technology continues to evolve and environmental requirements increase, galvanizing is an
“old craft” that is taking on new life and continues to play an irreplaceable and critical role in protecting steel, extending
its life and conserving resources. To choose galvanizing is to choose a long-lasting guarantee for your steel assets.