Clean external surface helps the next coating step. If not clean enough, you’d better define the corrosion level as ISO8501. We don’t suggest choosing surface of Grace C and Grade D, because a big effort will be taken to remove rust, such as sanding, shot blasting, etc.
Clean internal surface with fewer rust scrap, dust, and welding slag inside the pipe is more desirable, for better water/ gas flow. It is easy to check the interior condition of pipe by flashlight.
The quality and lifetime of coating are determined by layer thickness, adhesive force and smoothness, regardless of black painting, hot dip galvanizing or red oxide painting. It is better to use coating thickness gauge, to test 4-6 different points of each pipe.
Pipes must be welded or threaded for connecting other joints. So pipe end is crucial, but it is also fragile after beveling or threading. To keep good performance, plastic cap (insert or cover type), steel ring or end protector are used for protection.
Pipes shall be tied tightly into bundles, to avoid loosening in transportation and storage. But too many steel straps and steel bars will increase the weight significantly (mills take it as Net Weight to charge buyers). Also it can damage pipe coating or water-proof cloth wrapped nearby when loading.
Pipe shall always be stored in indoor warehouse, no matter in mill or seaport, so as to avoid rain and dust damage.
