Galvanized Steel Pipe

Galvanizing Methods for Seamless Steel Pipes

There are two main categories: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing includes wet process, dry process, lead-zinc process, redox process and others, with its technological process illustrated in the figure.

The core difference between various hot-dip galvanizing methods lies in the way to activate the steel pipe surface for improved galvanizing quality after pickling and cleaning. Currently, the dry process and redox process are predominantly adopted in industrial production, and their characteristics are listed in the table.

The zinc coating formed by electro-galvanizing features an extremely smooth, dense and uniform structure. It delivers excellent mechanical properties and corrosion resistance, with zinc consumption reduced by 60% to 75% compared with hot-dip galvanizing. Although electro-galvanizing involves relatively complex techniques, it is indispensable for single-sided coating, double-sided coating with different thicknesses on internal and external surfaces, and galvanizing of thin-walled steel pipes.