PREVENTION OF 3-LAYER POLYETHYLENE COATED PIPES FROM OVERPROTECTION BY COMPOSITE MAGNESIUM RIBBON ANODES

“Overprotection” occurs when 3-layer polyethylene coated pipe is cathodically protected with traditional block magnesium anode.To shoot the trouble,a novel composite magnesium ribbon anode is proposed.Several extruded magnesium ribbons in parallel are placed in a perforated plastic barrel with filling material.Each ribbon has its own conducting lead.The unique anode has larger working area and greater output current than the block anode with equal weight.In installation each ribbon anode is individually connected to aboveground test station,where it links to the pipe to be protected.Thus according to the extent of protection the number of working ribbon anodes could be varied and the anode output current could be adjusted.Practical engineering projects proved the new technique is successful in prevention from overprotection.