Bright Zinc Coating: The Preferred Surface Treatment for Excellent
Corrosion Resistance
In industrial manufacturing and the production of daily items, the
corrosion protection of metal substrates is crucial for ensuring
product lifespan and reducing maintenance costs. Bright zinc
coating, as a surface treatment that combines both decorative and
functional properties, has particularly outstanding corrosion
resistance, being able to build a reliable "protection barrier" for
steel and other substrates in various complex environments, making
it one of the preferred processes in numerous fields.
1. The core principle of bright zinc coating's corrosion
resistance: Dual protection mechanism
The corrosion resistance of bright zinc coating is not achieved
through a single mechanism but through the "physical isolation +
electrochemical protection" dual mechanism, which fundamentally
delays the corrosion of the substrate:
Physical barrier protection: During the zinc coating process, the
zinc layer evenly covers the surface of the substrate, forming a
dense metal film. This film can directly isolate the substrate from
air, moisture, dust, and other corrosive media, preventing the
initiation of oxidation reactions and electrochemical corrosion, as
if it were putting on a "protective coat" for the substrate.
Sacrificial anode protection: The electrode potential of zinc
(-0.76V) is lower than that of steel (-0.44V). When there is a
minor damage (such as scratches, bumps) to the zinc layer, the
exposed substrate and the zinc layer form an original battery, and
zinc will be the "sacrificing anode" to be corroded rather than the
steel substrate. This "self-sacrificing for the substrate"
characteristic ensures that even if the zinc layer is partially
damaged, it can continuously protect the substrate from rusting.
2. The corrosion resistance performance of bright zinc coating in
different environments (table comparison)
The corrosion resistance effect of bright zinc coating varies with
the intensity of environmental corrosion, but it is stable in
normal and low-corrosion environments, far exceeding that of
untreated substrates. The following is its performance comparison
in typical environments (taking steel substrates as an example):
| Application environment type | Environment characteristics | Untreated steel substrate lifespan | The lifespan of the glossy galvanized coating (with a conventional
zinc layer thickness of 8-12 μm) | Key anti-corrosion advantages |
| Indoor dry environment (such as offices, indoor areas of homes) | The humidity is relatively low (relative humidity < 60%), and
there are no obvious corrosive media. | 1-2 years (with a tendency for local rust spots) | 8 - 15 years (surface luster remains good, with no obvious
corrosion) | The physical barrier effect of the zinc layer is stable, without
additional corrosive pressure, and the lifespan is increased by
more than 8 times. |
| Outdoor natural environment (such as urban outdoors, non-industrial
areas) | Affected by rain and dew, it contains a small amount of dust and
sulfur dioxide. | 3 to 6 months (surface undergoes rapid oxidation and rusting) | 5 - 8 years (There may be slight zinc layer oxidation locally, but
the base material is not rusted) | The dual protection mechanism is activated, and even under the
influence of rainwater, the sacrificial anode can still protect the
substrate. |
| Moderate corrosion environment (such as industrial areas, coastal
suburbs) | Containing corrosive substances such as sulfur dioxide and chloride
ions, with high humidity | 1 - 3 months (severe rusting, base material becomes thinner) | 3 to 5 years (The zinc layer may experience local passivation layer
failure, and regular inspections are required) | It is necessary to be combined with passivation treatment (such as
colored passivation), which can further enhance the corrosion
resistance and extend the service life. |
| Highly corrosive environments (such as marine environments and
chemical workshops) | High salt fog, high concentration of acid and alkali vapors | ＜1 month (rapid rusting and scrap | 1-2 years (the zinc layer needs to be thickened to 15-20 μm +
passivation layer) | The process needs to be strengthened (by thickening the zinc layer
or applying a composite coating), but the lifespan of the treated
substrate is still more than 12 times longer than that of the
untreated base material. |
III. The Practical Application Value of Bright Zinc Coating's
Corrosion Resistance Performance
Due to its excellent corrosion resistance, bright zinc coating is
widely used in scenarios where longevity and reliability are
required:
In the home appliance sector: The metal shells and accessories of
refrigerators and washing machines are coated with bright zinc,
which not only maintains a beautiful metallic luster but also
resists the humid environment in kitchens and bathrooms, preventing
the shells from rusting and peeling off;
In building hardware: Door hinges, guardrails, pipe fittings, etc.,
for outdoor or semi-outdoor components, can withstand rain and
atmospheric corrosion through bright zinc coating, reducing
maintenance frequency;
In automotive parts: Concealed components such as chassis and
brackets, with the sacrificial anode protection of bright zinc
coating, can cope with muddy and waterlogged environments,
preventing components from rusting and breaking, and ensuring
driving safety.
Summary
With the "dual corrosion resistance mechanism", bright zinc coating
demonstrates excellent durability in conventional and low-corrosion
environments, while also considering cost advantages and processing
compatibility. Although it requires enhanced processing techniques
in high-corrosion environments, its overall corrosion resistance
performance still far exceeds untreated substrates, making it an
ideal choice for the "protection + aesthetics" dual requirements in
industrial and civilian fields. With the upgrading of processing
technology, the upper limit of corrosion resistance of bright zinc
coating will further increase, providing reliable metal protection
solutions for more scenarios.
Hot Rolled Cold Rolled Steel Sheet Coils Chemical Composition 304 Si≤1.00
