负向电压对海洋平台铝合金钻探管表面微弧氧化膜组织和耐蚀性影响

目的 提高海洋平台铝合金钻探管的耐腐蚀性能.方法 采用微弧氧化技术,在海洋平台钻探管用2 A12铝合金表面制备氧化铝陶瓷膜.通过盐雾试验,研究负向电压对微弧氧化膜耐腐蚀性的影响,并通过扫描电子显微镜和光学显微镜对微弧氧化膜的微观形貌、组织结构进行分析.结果 在微弧氧化处理过程中,随着负电压的升高,微弧氧化膜表面的孔径先增大后减小,膜表面变光滑.在一定负电压范围内,Al2 O3相的含量随负电压的升高先增加,当负电压达到一极限值后,Al2 O3相随负电压的升高而减少.负电压的增大能提高微弧氧化膜的耐腐蚀性,当负电压由8 V升高至24 V时,腐蚀速率由0.00568 g/(dm2·h)降低至0.00028 g/(dm2·h),前者是后者的20倍;当负电压为4 V时,部分膜层剥落,腐蚀严重;当负电压增至24 V时,有效延缓了微弧氧化膜的腐蚀程度.结论 在微弧氧化处理过程中,负电压对微弧氧化膜的制备有较大影响,增大负电压能有效提高微弧氧化膜的耐腐蚀性,此外基体本身所含的Fe、S等杂质是影响微弧氧化膜的主要因素.

Effect of Negative Voltage on Properties of Micro-arc Oxidation Coating Prepared on the Surface of Aluminum Alloy Drill Pipe in Offshore Platform

Objective To improve the corrosion resistance of the aluminum alloy drill pipe in offshore platform. Methods In this paper, the alumina ceramic membrane was prepared on the surface of 2A12 aluminum alloy for drill pipe in offshore platform by micro arc oxidation(MAO)technology. The effect of negative voltage on the corrosion resistance of MAO coatings was studied by salt spray test, and the microstructure and microstructure of MAO coatings were analyzed by scanning electron microscope and optical microscope. Results The negative voltage had a great influence on the preparation of MAO coating during the process of micro arc oxidation. The pore size of micro arc oxidation coating decreased with the increase of negative voltage, and the film surface became smoother. In addition, the content of Al2 O3 phase increased with the increase of negative voltage within a certain negative voltage range. When the negative voltage reached a limit value, the negative voltage increased with the decrease of Al2 O3 . The corrosion resistance of MAO coating could be improved as negative voltage increased. When the negative voltage was 8 V, the corrosion rate decreased from 0. 005 68 g / (dm2 ·h) to 0. 000 28 g / (dm2 ·h), which was 20 times higher than that at 24 V. When the negative voltage was 4 V, part of the coating was peeled off, and the corrosion was serious. When the negative voltage was increased to 24 V, the corrosion resistance of micro arc oxidation coating was effectively improved. Conclusion During the micro arc oxidation process, negative voltage had a great influence on the preparation of micro arc oxidation film. The corrosion resistance of micro arc oxidation could be effectively improved by increasing the negative voltage. In addition, Fe, S and other impurities in the matrix were the main factors that affected the corrosion resistance of micro arc oxidation coatings.