Hot-dip galvanized pipe: In order to improve the corrosion resistance of steel pipes, general steel pipes are galvanized.
Galvanized steel pipes are divided into two types: hot-dip galvanizing and electro-galvanizing. Hot-dip galvanizing has a thick zinc layer, while electro-galvanizing has a low cost and the surface is not very smooth.
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. In order 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. The steel pipe matrix undergoes complex physical and chemical reactions with the molten plating bath to form a corrosion-resistant zinc-iron alloy layer with a tight structure. The alloy layer, pure zinc layer and steel pipe matrix are integrated into one body. Therefore, it has strong corrosion resistance.
1. Uniformity of galvanized layer: The steel pipe sample shall not turn red (copper color) when immersed in copper sulfate solution for 5 consecutive times.
2. Surface quality: The surface of the galvanized steel pipe should have a complete galvanized layer, and there should be no uncoated black spots and bubbles. Small rough surfaces and local zinc tumors are allowed.
3. Weight of galvanized layer: According to the requirements of the purchaser, galvanized steel pipes can be used to measure the weight of the zinc layer. The average value should not be less than 500g/square meter, and any sample should not be less than 480g/square meter.
