1. Weld Defects in Plastic-Coated Steel Pipes: Severe weld defects are often remedied by manual mechanical grinding, resulting in uneven surfaces and affecting aesthetics. Acid pickling and passivation only on the weld seams also leads to uneven surfaces.

2. Difficulty in Removing Scratches from Plastic-Coated Steel Pipes: Overall, acid pickling and passivation cannot remove various scratches generated during processing, nor can they remove carbon steel, spatter, and other impurities adhering to the surface of the plastic-coated steel pipe due to scratches or welding spatter. This leads to chemical or electrochemical corrosion and rusting in the presence of corrosive media.

3. Uneven Grinding, Polishing, and Passivation of Plastic-Coated Steel Pipes: After manual grinding and polishing, acid pickling and passivation are difficult to achieve uniform treatment results for large workpieces, resulting in an unsatisfactory, uniform surface. Furthermore, labor and material costs are high.

4. Limited pickling ability of plastic-coated steel pipes: Pickling and passivation paste is not a panacea; it is difficult to remove black oxide scale produced by plasma cutting and flame cutting.

5. Severe scratches caused by human factors: During hoisting, transportation, and structural processing, scratches caused by impacts, dragging, hammering, and other human factors are relatively severe, increasing the difficulty of surface treatment and being a major cause of post-treatment corrosion.

6. Equipment factors affecting plastic-coated steel pipes: Scratches and creases caused during the bending and folding of profiles and plates are also a major cause of post-treatment corrosion.

7. Other factors affecting plastic-coated steel pipes: Impacts and scratches caused during the procurement and storage of raw materials for plastic-coated steel pipes due to hoisting and transportation are also relatively severe, contributing to corrosion.