To see the exterior surface of the pipe that has Zinc. Stick to the pipe surface like NG work or not to see if the flare surface has Zinc crack like NG work or not.
Observe the characteristics of the external surface of the pipeline, and see if there is zinc adhesion on the surface of the pipeline, which is the same as that of NG.<br>See if the flare page has zinc cracks like NG's work.