Why Use Hot-Dipped Galvanized Pipe?

History

• Hot-dipped galvanizing for steel pipes has been used since its commercialization in the 1850s. However, ancient artifacts reveal that zinc was used in construction as early as A.D. 79. Though the modern concept of galvanizing steel was introduced in France around 1742, the process itself was not patented until 1837. By 1850, the galvanized steel industry was using approximately 10,000 tons of zinc annually. As of November 2011, the American Galvanizers Association (AGA) estimates that American manufacturers use more than 600,000 tons of zinc annually to produce hot-dipped galvanized steel.

Production Process

• Holes bored into closed pipes before dipping ensure that galvanization occurs along both the interior and exterior surfaces of the steel. After the pipe is dipped into the molten zinc bath, the finished coating contains a total of four layers metallurgically bonded to one another and to the steel pipe. The metallic coating process contributes to the coating thickness and structural strength of the piping. Additionally, the outer layer, which comprises pure zinc, provides the piping with optimal protection against corrosion.

Structural Properties

• The primary benefit of hot-dipped galvanized steel pipes is that they are highly resistant to stress and corrosion compared to non-galvanized steel pipes. Galvanized coating creates a series of layers that become part of the underlying steel pipe. This creates a surface that can withstand substantial amounts of force exerted per square inch along the pipe’s surface. Additionally, galvanized steel performs well in wet environments and in coastal areas exposed to sea salt. Galvanized pipes are also highly resistant to chemicals with a high alkaline pH content. Furthermore, galvanizing ensures protection against rust, though occasional staining does occur due to the presence of iron.

Economic Benefits

• Hot-dipped galvanizing also has economic benefits. Federal regulations mandating the reduction of lead in zinc coatings have helped reduce pollutants such as smoke and top ash during production. Galvanized steel pipes also save energy and production costs. As of November 2011, the AGA states that the U.S. economy spends more than 3 percent of its gross domestic product (GDP) repairing and replacing steel products damaged by corrosion. Galvanized steel can prevent indirect costs, including traffic delays, automobile accidents and injuries caused by the failure of corroded steel pipes and structures.