Galvanized steel pipes come in two main types: cold galvanized steel pipes and hot-dip galvanized steel pipes. Among these, hot-dip galvanized steel pipes are extensively utilized across various industries including construction, mining, machinery, chemical processing, electrical power, rail transport, automotive production, highway infrastructure, bridge building, container manufacturing, sports facilities, agricultural machinery, petroleum extraction, geological exploration, greenhouse construction, and more.
A galvanized steel pipe is essentially a welded steel pipe that features either a hot-dip or electro-galvanized coating. This galvanization process enhances the pipe's corrosion resistance, thereby extending its lifespan. These pipes find widespread application beyond serving as basic fluid conduits like water, gas, and oil lines. They are also critical in sectors such as petroleum drilling where they serve as oil well casings and oil pipes, particularly in offshore operations. Additionally, they play a role in chemical processing for components like oil heaters, condensers, cooler tubes, coal distillation wash oil exchangers, and structural supports such as trestle piles and mine tunnel frameworks.
Hot-dip galvanizing involves immersing the steel pipe into molten zinc to create an alloy layer that bonds the zinc to the steel substrate. This method ensures a uniform and durable coating by first pickling the pipe to remove surface rust, followed by cleaning in an ammonium chloride or zinc chloride solution before immersion. The resulting zinc-iron alloy layer is tightly bonded to the steel substrate, providing excellent corrosion protection. This process creates a multi-layered structure where the alloy layer merges with both the zinc coating and the underlying steel, ensuring long-term durability.
On the other hand, cold galvanized pipes rely on electroplating for their zinc coating, which results in a much thinner layer—only about 10-50 grams per square meter. This makes their corrosion resistance significantly inferior compared to hot-dip galvanized pipes. Due to these limitations, reputable manufacturers typically avoid using cold galvanized pipes, reserving them instead for outdated setups where cost savings are prioritized over quality. Cold galvanized pipes have zinc coatings that merely adhere to the surface of the steel without forming a cohesive bond, making them prone to peeling and corrosion. Consequently, their reliability is questionable, leading to their prohibition in new housing projects for potable water and gas distribution systems. Government regulations have also mandated the phasing out of this older technology to promote safer, more durable alternatives in modern construction.
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