Hot-Dip Galvanized Square Pipe: This is a square pipe made by bending and welding steel plates or steel strips, and then placing the pipe into a hot-dip galvanizing bath where it undergoes a series of chemical reactions to form the final product. The production process for hot-dip galvanized square pipes is relatively simple, with high production efficiency and a wide range of specifications. The equipment and capital required for this type of pipe are minimal, making it suitable for small-scale galvanizing square pipe manufacturers. However, in terms of strength, these pipes are significantly weaker than seamless square pipes.
Cold galvanized square tubes are produced by applying a cold galvanized coating to the square tubes, thereby imparting corrosion resistance. Unlike hot galvanized coatings, cold galvanized coatings primarily undergo corrosion protection through electrochemical principles, necessitating thorough contact between the zinc powder and the steel to generate an electrode potential difference. Therefore, surface treatment of the steel is crucial.
Galvanized square tubes are divided into two main categories: hot-dip galvanized and electro-galvanized. Hot-dip galvanized methods include wet process, dry process, lead-zinc process, and redox process. The primary difference among these hot-dip galvanizing methods lies in the use of different techniques to activate the tube surface after acid pickling to improve galvanizing quality. Currently, the dry process and redox process are predominantly used, with their characteristics listed in the table. Electro-galvanized zinc coatings are extremely smooth, fine, and uniform in structure; they possess mechanical properties and corrosion resistance; and their zinc consumption is 60% to 75% lower than that of hot-dip galvanizing. Electro-galvanizing involves certain technical complexities, but it is necessary for single-sided coatings, double-sided coatings with different thicknesses on the inner and outer surfaces, and galvanizing of thin-walled tubes, among others.
