The waterflooding production is a major technique to keep strata pressure andenhance oil recovery at present, but it causes serious corrosion and scale problemsinevitably. Corrosion and scale during the oil field development severely influent oilfield production continuous, so it is an important and urgent issue which need to besolved. Electroless nickel-phosphorus coating can show excellent wear resistance,anti-corrosion properties, and so on. And its surface amorphous structure can preventcrysralline scale from adhering and growing. So the electroless plating Ni-P alloy onthe surface of the equipment and pipe in the system of water reinjection for oil fieldtreatment is a promised surface protection way to control the damage of corrosion andscale effectively. And the treatment coatings have well properties of corrosionresistance, scale resistance. Moreover, adding scale and corrosion inhibitor is also animportant and effective method to solve the problems of corrosion and scale in thesystem water reinjection. Chitosan is a kind of renewable resource widely existent innature. The experiment discussed significance to be green scale and corrosion inhibitorof chitosan by modification treatment. The objective is to give full play to theabsorotion property of hydroxyl and amino on chitosan. Therefore, the experimentsystematically discussed electroless Ni-P alloy coatings modified by adding rare earthNd, La, grain refiner PEG separately and together in chemical plating bath. Themorphology, microstructure, composition, hardness and toughness of the electrolessNi-P coatings were studied by using scanning electron microscopy, X-ray diffraction,micro-hardness tester and static indentation tester. Wear resistance property wasperformed using ball-on-disc tester. The corrosion resistance of coatings was evaluatedby electrochemical polarizati-on, impedance spectroscopy technique. And the anti-scale of coatings was analyzed and evaluated by contact angle, surface free energydetermination and coupon tests. All tests were supposed to reveal the mechanism ofcorrosion and scale inhibition; Chitosan-acrylamide graft copolymer with differentmolecular weight was synthesized after degraded by H2O2. The mechanisms ofcorrosion and scale inhibition were analyzed by electrochemical measurementtechnology and static scale inhibiton method. Both methods above will provide somenew effective ways to solve the problems of corrosion and scale in the system waterreinjection of oil field. The main conclusions as follows:1) Electroless deposited Ni-P coatings modified by rare earth Nd and La havegood anti-corrosion properties, wear resistance, surface hydrophobicity and anti-scaleproperties. The corrosion and scale resistance of the pipe surface of water reinjection inoil and gas field are improved significantly. The corrosion resistance of electrolessNi-P coatings modified by rare earth Nd is better than electroless Ni-P coating with thesame thickness. When0.06mmol/L Nd2O3and0.09mmol/L La2O3added, the preparedcoatings have the highest deposition rate and the good corrosion resistance and the lowsurface free energy when the deposited time is same, although the hardness and thewear resistance of electroless Ni-P coating modified by rare earth Nd decline slightly.The coupon tests indicate that the scale resistance of the electroless Ni-P coatingmodified by rare earth is improved significantly because of the good corrosionresistance and the lower surface free energy.2)Electroless deposited Ni-P coatings modified by PEG have good anti-corrosionproperties, wear resistance, surface hydrophobicity and anti-scale properties. Thecorrosion and scale resistance of the pipe surface of water reinjection in oil and gasfield are improved significantly. The molecular mass of PEG(2000,10000,20000) hasa distinct influence on surface free energy and corrosion resistance with the sameaddition. PEG2000has the best corrosion and scale inhibition among these. When4mg/L PEG2000added, the prepared coating has the highest deposition rate. The grainsize of the coating surface became smaller obviously. The corrosion and scaleresistance of the electroless Ni-P coatings modified by rare earth are improvedsignificantly, but the corrosion and scale resistance was impacted asynchronously asthe addition of PEG.3) The properties of electroless Ni-P platings modified by rare earth Nd or La andPEG together are worse than the platings modified by rare earth Nd, La, PEGseparately. The deposition rate, hardness, corrosion and scale inhibition of the coating increase relative to the substrates, but decrease obviously relative to the platingsmodified separately.4) The corrosion and scale resistance of chitosan with different molecular weightafter degradation by H2O2/HAC system grafted with acrylamide is compared. Theresults indicate that chitosan-acrylamide graft copolymer which has9.8×104molecularmass has the best effective to corrosion inhibition. Corrosion inhibition efficiency ismore than60%; In the respect of scale inhibition, the efficiency of chitosan-acrylamidegraft copolymer reduce as the molecular mass of chitosan decrease. |