Uniformity of galvanized layer Galvanized steel pipes should be tested for uniformity of galvanized layer. The steel pipe sample shall not turn red (copper-plated color) when immersed in copper sulfate solution for 5 consecutive times.

1. Standard classification of galvanized pipes

General steel pipes (black pipes) are galvanized to improve the corrosion resistance of steel pipes. Galvanized steel pipes are divided into hot-dip galvanizing and electric steel zinc. Hot-dip galvanizing has a thick zinc layer and electro-galvanizing has a low cost. Galvanized pipes are divided into two types: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing has a thick zinc layer and has the advantages of uniform coating, strong adhesion, and long service life. The cost of electroplated galvanizing is low, the surface is not very smooth, and its corrosion resistance is much worse than that of hot-dip galvanized pipes.

Hot-dip galvanized pipe:

Hot-dip galvanizing pipe reacts molten metal with an iron matrix to produce an alloy layer, thereby combining the matrix and the coating. Hot-dip galvanizing is to pickle the steel pipe first. To remove the iron oxide on the surface of the steel pipe, after pickling, it is cleaned in an aqueous solution of ammonium chloride or zinc chloride or a mixed aqueous solution of ammonium chloride and zinc chloride and then sent to in a hot dip plating tank. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion, and long service life.

Hot-dip galvanized steel pipe: The steel pipe matrix undergoes complex physical and chemical reactions with the molten plating solution to form a corrosion-resistant zinc-iron alloy layer with a tight structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.

Cold galvanized pipe:

Cold galvanizing is electro-galvanizing. The amount of galvanizing is minimal, only 10-50g/m2. Its corrosion resistance is much worse than that of hot-dip galvanized pipes. The zinc layer is electroplated, and the zinc layer is independently layered with the steel pipe matrix. The zinc layer is thin, and the zinc layer adheres to the steel pipe matrix, and falls off easily. Therefore, its corrosion resistance is poor.

2. Application of galvanized pipe:

Galvanized pipe has the advantages of uniform coating, strong adhesion, and long service life.

A galvanized pipe is a welded steel pipe with a hot-dip or electroplated zinc layer on the surface. Galvanizing can increase the corrosion resistance of steel pipes and extend their service life. Galvanized pipes are widely used. In addition to being used as pipeline pipes for general low-pressure fluids such as water, gas, and oil, they are also used as oil well pipes and oil pipelines in the petroleum industry, especially offshore oil fields, and as oil heaters and condensators in chemical cooking equipment. Pipes for coolers, coal distillate wash oil exchangers, pipes for trestle pipe piles, support frames for mine tunnels, etc.

3. Unique cleaning process for galvanized pipes:

The galvanized pipe adopts the sulfate electroplating process of zinc-iron alloy, which means that there are direct perforations between the production line troughs and the troughs without any carry-out or overflow of the solution. Each process of the production process is composed of a circulation system. The solutions in each tank, namely acid and alkali, electroplating, light extraction and passivation, etc., are only recycled and not leaked or discharged outside the system. The production line only has 5 cleaning tanks, which use circulation. Reuse and discharge regularly, especially in production processes that do not produce wastewater without cleaning after passivation.