Importance of zinc layer of galvanized coil

The zinc layer of galvanized coil is one of its core performance indicators, which directly determines the corrosion resistance, service life and application range of the product. The following is a detailed analysis of the importance of the zinc layer:

1. Anti-corrosion protection
Barrier effect: The zinc layer isolates the steel from oxygen and moisture, preventing the iron substrate from oxidation (rusting).

Sacrificial anode protection: Even if the zinc layer is partially damaged, the zinc will corrode preferentially (electrochemical protection) to protect the substrate from erosion.

Applicable environment: The thicker the zinc layer, the stronger the corrosion resistance in harsh environments such as humidity, salt spray (coastal areas), and industrial pollution.

2. Impact on product life
The thickness of the zinc layer is positively correlated with the life: For example, the corrosion resistance life of Z60 (zinc layer 60g/m²) is usually 2-3 times longer than that of Z20.

Economic trade-off: Although the thick zinc layer costs more, it can reduce the frequency of maintenance and replacement and is more economical in the long run (such as building roofs and bridge structures).

3. Application scenario requirements
Construction industry (roofs, wall panels): Z120-Z275 (high weather resistance) is required.

Home appliance panels (refrigerators, air conditioners): Z60-Z120 is commonly used, taking into account both aesthetics and rust prevention.

Auto parts: Galvanized sheets need to be matched with the coating process, and the zinc layer is usually thin (Z30-Z60).

Power facilities (transmission towers): Z150 or above is required to cope with long-term outdoor exposure.

4. Processing performance impact
Weldability: Too thick a zinc layer may cause welding pores, and the process needs to be adjusted (such as laser welding or reducing the thickness of the zinc layer).

Formability: The bonding strength between the zinc layer and the substrate affects the surface quality during stamping and bending (such as the risk of zinc layer falling off).

5. Zinc layer standards and classification
International standards:

ISO 3575 (commercial grade, stamping grade, etc.).

ASTM A653 (American standard, such as G60, G90, unit oz/ft²).

Zinc layer code:

DX51D+Z60: general use, zinc layer 60g/m² (double-sided).

DX53D+ZF80: for deep drawing, zinc-iron alloy layer 80g/m².

6. Zinc layer process selection
Hot-dip galvanizing (HDG): low cost, thicker zinc layer (commonly 10-50μm), suitable for heavy corrosion protection.

Electrogalvanizing (EG): thin zinc layer (3-20μm), uniform surface, suitable for precision machining.

Zinc alloy coating (such as Zn-Al, Zn-Mg): further improves corrosion resistance (2-4 times higher than pure zinc layer).

7. Risk of quality defects
Zinc layer detachment: caused by insufficient substrate cleanliness or process problems.

Uneven zinc flowers: affects appearance (such as home appliance panels require no zinc flowers or small zinc flowers).

White rust: caused by condensed water during transportation or storage, requiring oiling or chromate treatment.

Summary
The zinc layer is the soul of the performance of galvanized coils, and needs to be comprehensively selected according to the application scenario, cost budget and processing requirements. For example:

Building structure: give priority to thick zinc layer (Z180 or above).

Household appliance shell: balance the adhesion of zinc layer and surface coating (Z60-Z100).

Automotive sheet: use alloy plating or composite process (such as galvanizing + phosphating).

Rational selection of zinc layer can significantly improve product competitiveness and avoid the risk of over-design or insufficient protection.