The main function of the zinc layer is to protect the base metal from corrosion. In a humid environment, zinc is more active than iron, so it will undergo oxidation reaction before iron, thus protecting the internal iron from corrosion. The thickness of the zinc layer directly affects the durability of its protective effect. A thicker zinc layer provides longer-lasting protection, extending the life of the product.

The thickness of the zinc layer on galvanized sheets varies according to different application requirements and international standards. Generally, the zinc layer of hot-dip galvanized steel sheets is thicker than that of electro-galvanized steel sheets. The thickness of the zinc layer of hot-dip galvanized sheet is generally between 5-150 microns. According to the quality of the zinc layer, it can be divided into different grades, such as Z100, Z150, Z200, Z275 and Z600. These grades indicate the double-sided galvanizing amount in grams per square meter. The electroplated zinc coating is relatively thin, with a thickness usually between 5 and 30 microns.

The thickness of the zinc layer of alloyed galvanized steel sheet is similar to that of hot-dip galvanizing, but the zinc layer is more tightly bonded to the steel sheet. The thickness of the zinc layer can be measured by the amount of zinc attached (such as the zinc content per square meter). The thicker the layer, the stronger the corrosion resistance is. The selection should be determined in combination with the degree of corrosion in the use environment.

Coating Uniformity: Inspect whether the zinc layer on the steel pipe surface provides complete coverage, free from missed plating, nodules, or noticeable color variations. Inferior products often exhibit zinc layer peeling or localized darkening.
Surface Finish: High-quality galvanized pipes feel smooth to the touch, without burrs or unevenness; low-grade products may retain rust spots due to incomplete acid pickling.
Marking Clarity: Reputable manufacturers clearly mark specifications, standard numbers (e.g., GB/T 3091), and company names on the pipe body. Be wary of blurred or missing markings.
Additionally, cut a sample to inspect the cross-section. A high-quality zinc coating adheres tightly to the base pipe without delamination.

1. Thickness Differences: The hot-dip galvanized zinc layer itself is relatively thick, generally over 10µm thick, which provides excellent corrosion resistance. While the surface is bright, it is slightly rough and may show zinc spangles.
Electro-galvanized steel, on the other hand, has a thinner zinc layer, approximately 3-5µm thick. While smooth, it can appear dull and smudged. While workability is good, corrosion resistance is limited.

2. The surface of hot-dip galvanized steel is a pure zinc coating, which is uniform and has no pores. However, there is a layer of relatively brittle compound between the coating and the substrate.
The electro-galvanized coating is composed of only zinc atoms, which are deposited on the surface of the steel strip. It is a physical adhesion effect and has many pores on the surface, so it is more susceptible to corrosion.

3. Hot-dip galvanizing uses the alloying reaction of metallic zinc and iron at high temperature to form a zinc-iron alloy layer on the surface of steel. The process is relatively complex and has certain requirements for steel, but the coating is stronger, more corrosion-resistant, and has a wider range of applications.
Electrogalvanizing is the process of forming a zinc layer on the surface of steel using electrochemical principles. The process is simple, environmentally friendly and low-cost, but the coating is thin, the adhesion between the zinc layer and the steel substrate is poor, and its scope of application is narrow.