To enhance the corrosion resistance of steel pipes, they are commonly coated with zinc. This process results in two main types: hot-dip galvanized and electro-galvanized pipes. Hot-dip galvanizing provides a thicker zinc layer, offering better protection against rust, while electro-galvanizing is more cost-effective but often produces a less smooth surface. Another type, known as oxygen-blowing welded pipes, is typically used for low-pressure gas applications and comes in small diameters, ranging from 8/8 to 2 inches. These pipes are made from steel strips such as 08, 10, 15, 20, or Q235 grades, and to prevent corrosion, some are treated with aluminum coating.
Galvanized pipes were widely used in older buildings for water supply systems, and even today, they are still found in gas and heating pipelines. However, over time, these pipes tend to corrode, leading to the formation of rust inside the walls. This can result in discolored, yellowish water that not only stains fixtures but also harbors bacteria. The buildup of rust increases the concentration of heavy metals in the water, which poses serious health risks. In the 1960s and 1970s, many developed countries began phasing out galvanized pipes and introduced newer materials. In China, the Ministry of Construction and other government agencies issued regulations banning the use of galvanized pipes for cold water systems starting in 2000. Today, they are rarely used in new residential areas for cold water, though some regions still use them for hot water piping due to their durability and cost-effectiveness.
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