What is the difference between hot dipped galvanizing and pre-galvanizing?

The hot-dip galvanized pipe is to make the molten metal react with the iron matrix to produce an alloy layer, so that the matrix and the coating are combined. Hot-dip galvanizing is to pickle the steel pipe first. It is cleaned in the tank of ammonium chloride or zinc chloride aqueous solution or mixed aqueous solution of ammonium chloride and zinc chloride, and then sent to the hot dip coating tank. Hot dip galvanizing has the advantages of uniform coating, strong adhesion, strong corrosion resistance, and long service life.

Pre-Galvanizing

The processing technology of pre-galvanized steel pipe differs from that of hot-dip galvanizing mainly in the raw materials used. The raw materials of pre-galvanized steel pipes are mainly galvanized steel coils. After the factory processes the galvanized coil into a steel pipe, it is no longer necessary to galvanize again, and it is only necessary to supplement zinc on the welded part. The advantage of pre-galvanizing is that the zinc layer is more uniform and the appearance is more beautiful. The pre-galvanizing process is favored by people because of its low plating cost, excellent protection properties and beautiful appearance, and is widely used in construction, machinery, solar energy and other fields.

The thickness of the zinc layer of hot-dip galvanizing is 100-500 g/㎡, and the thickness of the zinc layer of pre-galvanized steel pipe is 40-100 g/㎡.

Therefore, hot-dip galvanized steel pipe has better corrosion resistance than pre-galvanized steel pipe.