Galvanized steel coils are ubiquitous, from towering skyscrapers to speeding cars and everyday appliances. Statistics show that more than half of the world’s zinc production is used for galvanizing.

As a crucial metal material, the performance of galvanized steel coils largely depends on the thickness of their zinc coating. Different applications have varying requirements for zinc coating thickness, and to meet diverse needs, various zinc coating specifications have been established. This article will provide a detailed analysis of the meanings behind these specifications and how to select suitable zinc coating specifications based on different application scenarios.

Methods for Expressing

SI (Metric) System: Expressed as the weight of zinc per square meter (g/m²), e.g., Z90 indicates a zinc coating weight of 90 g/m².

Imperial System: Expressed as the weight of zinc per square foot (oz/ft²), e.g., G30 indicates a zinc coating weight of 0.3 oz/ft².

Conversion Example:

Using the conversion factors of 1 ounce ≈ 28.35 grams and 1 square foot ≈ 0.0929 square meters, we can calculate that G30, which represents 0.3 ounces of zinc per square foot, is approximately equivalent to 91.4 grams of zinc per square meter.

Here are some common similar specifications:

Relationship between Zinc Coating Thickness and Weight

The density of zinc is approximately 7.14 g/cm³. Therefore, the average zinc coating thickness can be calculated based on the coating weight:
Zinc coating thickness (micrometers) ≈ Zinc coating weight (g/m²) ÷ 7.14

Comparison under Different Standards

Selection

• Corrosion Resistance: A thicker zinc coating forms a more dense protective layer, enhancing corrosion resistance. Since zinc is more reactive than iron, it preferentially oxidizes in corrosive environments, protecting the underlying steel substrate.
• Formability: An excessively thick zinc coating can reduce the material’s formability, increase processing difficulty, and potentially lead to surface cracking.
• Paintability: Zinc coating thickness affects the adhesion of coatings. Both excessively thick and thin zinc coatings can negatively impact the durability of coatings.
• Weldability: Zinc coatings can affect welding performance. Excessive zinc thickness can easily lead to porosity during welding, affecting weld quality.
• Cost: Increasing zinc coating thickness increases costs.

When selecting the appropriate zinc coating specification, it is essential to consider factors such as the application environment, processing methods, and cost.

Measurement Methods

Factors Affecting Zinc Coating Thickness

• Galvanizing Process: Different processes, such as hot-dip galvanizing and electroplating, produce zinc coatings of varying thicknesses.
• Base Material: The composition and surface condition of the base material affect the adhesion and thickness of the zinc coating.
• Galvanizing Solution Composition: The composition and temperature of the galvanizing solution affect the growth rate and crystal morphology of the zinc coating.
• Process Parameters: Process parameters such as galvanizing speed and cooling rate affect the thickness and uniformity of the zinc coating.

Hazards and Prevention Measures for Non-Uniform Zinc Coatings

Summary

Zinc coating specifications significantly influence the performance of galvanized steel coils. Selecting the appropriate zinc coating specification is crucial for ensuring product quality and service life. When choosing galvanized steel coils, it is essential to consider factors such as the application environment, processing methods, and cost, and consult with technical experts. Contact our team now!