Hot-dip galvanized steel pipes are produced by reacting molten metal with an iron substrate to create an alloy layer, thereby combining the substrate and the coating. The process involves first pickling the steel pipes to remove iron oxide from their surfaces. After pickling, the pipes are cleaned in an aqueous solution of ammonium chloride, zinc chloride, or a mixture of both, and then fed into a hot-dip galvanizing bath.
Hot-dip galvanizing boasts several advantages, including even coating, strong adhesion, and long service life. The steel pipe substrate undergoes complex physical and chemical reactions with the molten galvanizing solution, resulting in the formation of a corrosion-resistant, tightly structured zinc-iron alloy layer. This alloy layer merges seamlessly with the pure zinc layer and the steel pipe substrate, conferring high corrosion resistance.
Uniformity of the Galvanized Layer: Steel pipe samples should not turn red (copper-plated color) after being continuously immersed in a copper sulfate solution five times.
Surface Quality: The surface of hot-dip galvanized steel pipes should have a complete galvanized layer, free from uncoated black spots and bubbles. Minor roughness and localized zinc tumors are acceptable.
Weight of the Galvanized Layer: As per the buyer's requirements, the weight of the galvanized layer on steel pipes can be measured, with an average value not less than 500g per square meter. The weight of any individual sample must not be less than 480g per square meter.
