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. In order to remove the iron oxide on the surface of the steel pipe, after pickling, 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 in the hot dip bath. Hot-dip galvanizing has the advantages of uniform coating, strong adhesion and long service life. The steel tube substrate undergoes complex physical and chemical reactions with the molten plating solution to form a corrosion-resistant zinc-iron alloy layer with a compact structure. The alloy layer is integrated with the pure zinc layer and the steel pipe matrix. Therefore, it has strong corrosion resistance.
1. Uniformity of galvanized layer: The steel pipe sample shall not turn red (copper-plated color) after being continuously dipped in copper sulfate solution for 5 times.
2. Surface quality: The surface of the galvanized steel pipe should have a complete galvanized layer, and there should be no unplated black spots and bubbles, and small rough surfaces and local zinc tumors are allowed.
3. Weight of galvanized layer: According to the requirements of the buyer, the weight of galvanized steel pipe can be measured for the weight of zinc layer.
Cold galvanized pipe
Cold galvanizing is electric galvanizing, and the amount of galvanizing is very small, only 10-50g/m2. Its corrosion resistance is much different than that of hot-dip galvanized pipes. In order to ensure the quality, most regular galvanized pipe manufacturers do not use electro-galvanized (cold plating). Only those small enterprises with outdated equipment use electrogalvanizing, and of course their prices are relatively cheap. The Ministry of Construction has officially issued a document to eliminate cold galvanized pipes with backward technology, and cold galvanized pipes are not allowed to be used as water and gas pipes in the future. The zinc layer is an electroplating layer, and the zinc layer is independently layered with the steel pipe substrate. The zinc layer is thin, and the zinc layer is simply attached to the steel pipe substrate and is easy to fall off. Therefore, its corrosion resistance is poor. In newly built houses, it is forbidden to use cold galvanized steel pipes as water supply pipes.
How to distinguish galvanized steel pipe can start from its specifications, just from the nominal diameter classification, there are 6, 8, 10, 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 155mm and other lengths, the nominal diameter The larger the quality, the higher the general quality and the higher the price. Galvanized steel pipes are also divided into ordinary steel pipes and thickened steel pipes. Thickened steel pipes are heavier than ordinary steel pipes, but after galvanizing The weight coefficient is smaller for the thickened steel pipe. In addition, the weight of the galvanized layer of the hot-dip galvanized steel pipe is also required. The quality of the galvanized layer can be measured according to your own needs. Generally, we stipulate that the average value of the galvanized layer should be Not less than 0.5kg per square meter.