ZMU coating is a coating applied to external surface of the ductile cast iron pipes. It provides two functions:
• A mechanical protection of the wall of the pipes to face the mechanical solicitations during handling, transport, and laying of pipes in the soil.
• A protection against corrosion, in particular in the soil.
Today, ZMU coating, retained by PAM China, is a protection system including several layers deposited successively on the external wall of the pipe:
• First layer consisting in the deposit of 99.9% pure zinc by electric arc spraying, with a surface density of 130 g/m ², directly applied to the pipe wall provided with its oxide skin resulting from the heat treatment.
• Second interstitial layer of a glue paint containing epoxy resin in thickness ranging between 70 and 100 µm.
• Last layer of a cement mortar, composed of fine sand (size of the grains enters and mm), of blast furnace cement, plastic fibers and specific admixtures. A layer thickness of at least 5 mm, is applied to the glue paint at the beginning of reticulation.