Corrosion Resistance of Electroless Nickel-Phosphorous Coating on Drill-Pipe in Fresh-Water Mud

Electroless Ni-P coating with high phosphorus content was prepared on G105 drill-pipe to improve the corrosion resistance in fresh-water mud. A scanning electron microscope equipped with an energy dispersive spectrometer attachment was performed to observe the morphology of as-plated Ni-P coating and determine its composition as well,while a thickness gauge was performed to measure the thickness of the coating.In the meantime,the effect of flow rate on the corrosion rate of G105 steel and electroless Ni-P coating was investigated with a dynamic simulation corrosion test device; and the high temperature corrosion resistance and abrasion-corrosion resistance of organic coatings currently used at oilfields were compared with those of electroless Ni-P coating.Results indicated that as-plated electroless Ni-P coating had cell-like appearance and contained 13.23%P,belonging to corrosion-resistant coating with high content of P.Besides,flow rate had minor effect on the corrosion rate of electroless Ni-P coating,and asplated Ni-P coating possessed much better corrosion resistance than G105 steel substrate.Moreover,the organic coatings were liable to destruction after 10 h of enhanced abrasion,while electroless Ni-P coating remained unaltered even after 50 h of enhanced abrasion under the same condition.In addition,under low flow rate,the organic coatings were liable to bubbling after 10 h of enhanced abrasion,but electroless Ni-P coating remained unchanged under the same condition.