What Are the Differences Between Galvanized Strip Pipes and Hot-Dip Galvanized Pipes?

Galvanized pipe, also known as pre-galvanized pipe, looks bright to the naked eye and has a smooth and beautiful surface. Strictly speaking, it is also a type of hot-dip galvanized pipe, but the processing process is different. Galvanized strip pipes are generally made by first coating the bare narrow strip with zinc through continuous hot-dip galvanizing equipment, processing it into a galvanized strip, and then welding the galvanized strip into a galvanized pipe.

Galvanized steel pipe is a metal material with excellent properties. Compared with hot-dip galvanized pipe, it has the following differences:

1. Different processes

Hot-dip galvanized pipes are made by immersing steel pipes in molten zinc liquid for galvanizing, while galvanized strip steel pipes use an electroplating process to evenly coat the zinc layer on the surface of the steel strip.

2. Different structures

Hot-dip galvanized pipe is a tubular product, while galvanized strip steel pipe is a strip-shaped product with larger width and smaller thickness.

3. Different uses

Hot-dip galvanized pipes are mainly used to transport liquids and gases, such as water supply pipelines, oil pipelines, etc.; while galvanized steel pipes are mainly used to manufacture various metal products, such as auto parts, home appliance casings, etc.

4. Different anti-corrosion properties

Hot-dip galvanized pipes have better anti-corrosion properties because of their thicker zinc layer; while galvanized steel pipes have relatively poor anti-corrosion properties because of their thin zinc layers.

5. Costs are different

The production process of hot-dip galvanized pipes is relatively complex and the cost is high; while the production process of galvanized steel pipes is relatively simple and the cost is low.

6. Appearance difference

(1) The color of hot-dip galvanized pipe is a bit white; while the color of galvanized pipe is a bit bluish.

(2) Hot-dip galvanized pipes are white but neither shiny nor reflective, with many snowflake-like shapes on the surface, and zinc nodules (condensed zinc) on both ends; while galvanized pipes are white, shiny and reflective, with very few snowflake-like shapes, both ports are clean and free of zinc tumors.

In short, there are obvious differences between galvanized strip steel pipes and hot-dip galvanized pipes in terms of process, structure, use, anti-corrosion performance and cost. As a core product, galvanized steel pipe has unique advantages and wide application prospects, and can meet the needs of various industries.

How to judge the quality of hot-dip galvanized pipes

1. Appearance of galvanized pipe fittings

The surface of high-quality galvanized pipe fittings should have a complete coating with consistent color, uniform transition, and no sags, drips, or excess agglomerations on the surface. There must be no defects such as missing plating or exposed iron on the surface of pipe fittings.

2. Thickness of galvanized layer

The thickness of the zinc layer of galvanized pipes is an important indicator for judging the quality of galvanizing. It is generally expressed in units of μm. It can also be expressed by the weight of the zinc layer per square meter(g/m²⁾. The conversion formula is: 1g/m2=0.14μm. Since zinc and steel have different magnetism and polarizability, the thickness of the zinc layer can be measured non-destructively with a galvanized layer thickness gauge. To determine the weight of the zinc layer, you need to scrape the zinc layer and sample it, and measure it with chemical methods such as the antimony chloride method.

3. Uniformity of galvanized layer

The high-quality galvanized layer has uniform texture, no leakage plating or post-plating damage, and the galvanized pipe can be immersed in a certain concentration of copper sulfate solution for a certain number of times and time, if there is no red extract (metal copper) on the surface, it can be considered that the galvanized pipe has no leakage plating and post-plating damage defects.

4. Adhesion of galvanized layer

The adhesion of galvanized layer is the standard to measure the firmness of the combination of galvanized layer and steel pipe. After the steel pipe is immersed in the zinc pool for a certain time, the surface of the steel pipe will react with the galvanized liquid to form a zinc-iron mixed layer. Scientific and sophisticated galvanizing process can form a zinc-iron mixed layer of sufficient thickness to improve the adhesion of zinc layer. The adhesion of the galvanized layer can be monitored by tapping the rubber mallet, so that the coating does not fall off after tapping a certain number of times.