Pre Galvanized Steel Pipe

Galvanized Steel Pipe Introduction

Galvanized steel pipes are divided into hot-dip galvanized steel pipes and pre-galvanized steel pipes, which are welded steel pipes with a galvanized layer on the surface. Galvanizing can increase the corrosion resistance of the steel pipe and extend its service life.

Hot-dipped galvanized pipes create an alloy layer by reacting molten metal with the iron matrix, thereby combining the matrix and the coating. The process involves pickling the steel pipe to remove surface iron oxide, followed by rinsing in an aqueous solution of ammonium chloride or zinc chloride, or a mixed solution of ammonium chloride and zinc chloride, before immersion in the hot-dip galvanizing bath. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life. The complex physical and chemical reactions between the base of the hot-dip galvanized steel pipe and the molten coating form a tightly structured zinc-iron alloy layer with strong corrosion resistance. Hot dipped galvanized pipes have a wide range of uses, including not only as pipeline pipes for general low-pressure fluids such as water, gas, and oil, but also as oil well pipes and oil transmission pipes for the petroleum industry, especially offshore oil fields, as well as pipes for oil heaters, condensers, coal tar washing oil exchangers in chemical and coking equipment, and for pile pipes in wharves and support frames in mine tunnels.

Pre-galvanized pipes have a very small amount of zinc coating, only 20-50g/m2, and their corrosion resistance is much lower than that of hot-dip galvanized pipes. Pre-galvanized pipes cannot be used for water and gas pipelines. The zinc layer of pre-galvanized steel pipes is thin and simply adheres to the steel pipe base, making it prone to peeling off, resulting in poor corrosion resistance.

Hot Galvanized Pipe V.S. Pre Galvanized Pipe