• .Purpose: It is a process where a protective zinc layer is applied to steel to prevent rust and corrosion.
• Main Method (Hot-Dip): The most common method involves cleaning the steel and then dipping it into a bath of molten zinc, which creates a thick, durable coating.
• Key Advantage: The zinc coating acts as a physical barrier. Crucially, it also provides "sacrificial protection," meaning it will corrode before the steel does, even if the coating is scratched.
• Result: This process creates a long-lasting, cost-effective shield, making it ideal for outdoor structures, automotive parts, and countless other applications exposed to the elements.

Galvanized Test Method：

1.Thickness(The Most) :

A: Magnetic Thickness Gauge （The Most）

Operates on the magnetic induction principle. The zinc coating is non-magnetic, while the steel substrate is magnetic. The thickness is derived by measuring the change in magnetic flux between the probe and the substrate. It is a non-destructive, fast, and portable method.

B: Metallographic Microscopy

The galvanized sample is cross-sectioned, mounted, polished, and etched to create a metallographic specimen. The coating thickness is directly measured under a microscope. This method is considered a reference standard but is destructive and time-consuming.

C: Gravimetric Method - Weighing

The zinc coating is completely dissolved using a stripping solution that does not attack the steel substrate. The mass of the coating is determined by the weight difference before and after stripping, calculating the mass per unit area (e.g., g/m²). This is another reference method and is destructive.

2.Uniformity Inspection

The galvanized article is immersed in a standardized copper sulfate solution. The test qualitatively assesses the coating's uniformity and density by counting the number of immersions required until copper metal (a reddish deposit) appears. More immersions indicate a better, more robust coating.

3.Adhesion Test

A: Impact/Grid Test

A specialized hammer is used to impact the coating, or a knife is used to cut a grid pattern into it. The coating is then inspected for flaking or peeling. This is a qualitative method to evaluate the bonding strength between the coating and the substrate.

B: Bend Test

The galvanized sample is bent around a mandrel of a specified diameter (usually 90° or 180°). The outer surface of the bend is examined for cracking or flaking of the zinc coating. It assesses the coating's ductility and adhesion.

4.Appearance & Composition Inspection

A:Visual Inspection

The most basic method. The coating surface is inspected for smoothness, continuity, and the absence of defects such as bare spots, drips, lumps, cracks, or blisters.

B:Alloy Layer Structure Analysis

Often combined with metallography. The cross-section is examined under a microscope to analyze the structure, thickness, and continuity of the zinc-iron alloy layers (Gamma, Delta, Zeta, Eta), which directly affect the coating's mechanical properties and corrosion resistance.