Common Defects and Causes of Spiral Steel Pipes: Loosening, bubbles, shrinkage cavities, residues, non-metallic inclusions, segregation, white spots, cracks, and various abnormal fracture defects in spiral steel pipes.

Causes of Segregation in Q235 Spiral Pipes: During casting and solidification, selective crystallization and diffusion can cause the aggregation of certain elements, leading to uneven chemical composition. Depending on the distribution location, this can be classified as ingot segregation, center segregation, and point segregation.

Causes of porosity in Q235 spiral tubes: During hot working, gaps are created by the solidification shrinkage of low-melting-point materials and the release of gas, preventing the steel from being welded. Based on their basic distribution, porosity can be divided into two types: centrally located type and generally loose type.

You can paint them, but not directly.

Since galvanized pipes have a smooth surface and a highly reactive zinc coating, they must first be cleaned and sanded, then coated with a specialized primer (such as epoxy zinc yellow primer or zinc phosphate primer), followed by a compatible topcoat (such as epoxy paint, polyurethane paint, or water-based acrylic paint). At the same time, avoid using ordinary latex paint, paints containing copper pigments, and alkyd paints, as these can cause peeling, flaking, or accelerated corrosion.

The coating scheme for anti-corrosive spiral steel pipes is determined by the operating environment.

The three-layer polyethylene (3PE) coating system combines epoxy powder, an adhesive layer, and a polyethylene layer to form a structurally stable protective barrier.

Epoxy coal tar coating involves the alternating application of epoxy coal tar paint and glass fiber cloth, creating a water- and corrosion-resistant coating system. Internal cement mortar lining forms a smooth inner surface on the pipe wall, helping to reduce flow resistance.

Epoxy powder coating utilizes high-density polyethylene as a base material, balancing mechanical strength with corrosion resistance. Each process has its own specific advantages; the appropriate method should be selected based on the conveyed medium and installation conditions.