Description

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, oxidation-reduction process and others, and its technological process is shown in the figure.

The main difference between various hot-dip galvanizing methods lies in the way to activate the pipe surface to improve galvanizing quality after pickling and cleaning the steel pipes. At present, the dry process and oxidation-reduction process are mainly adopted in production, and their characteristics are listed in the table.

The zinc coating of electro-galvanizing features an extremely smooth and dense surface with uniform structure; it possesses good mechanical properties and corrosion resistance; its zinc consumption is 60%～75% lower than that of hot-dip galvanizing. Electro-galvanizing involves certain technical complexity, yet it is indispensable for single-sided coating, double-sided coating with different thicknesses on inner and outer surfaces, and galvanizing of thin-walled pipes.