What are the standards for the thickness of the anti-corrosion layer of the 3-layer PE anti-corrosion spiral welded steel pipe? The diameter of the 3-layer PE anti-corrosion spiral welded steel pipe is generally DN20 to DN2600, and the thickness of the anti-corrosion layer varies depending on the size of the diameter. When the diameter of the steel pipe is less than DN100, the thickness of the ordinary level anti-corrosion layer is 1.8mm, and the reinforced level is 2.5mm.