Study On Corrosion Resistance Of Al₂O₃-CeO₂-Y₂O₃Nanocomposite Coating

With the rapid development of modern industry, the working condition of the usingenvironment of iron and steel materials in metallurgy, chemical industry, construction,aerospace, medicine, and other departments is increasingly strict. As we know thecorrosion problem is getting worse, looking for a new kind of anti-corrosion passivationtechnology has become the top priority. Nanocomposite coating is attracting more attention,because of its superior protection, surface decoration and excellent performanceimprovement. The main aim of this study is to preliminaries explore the processing andanti-corrosion property of Al2O3-CeO2-Y2O3nanocomposite coating on SS304by sol-gelspin coating method. The primary salt was Al (NO3)3.This technological process is simpleand easy to operate. Compared to the thermal spraying and physical (chemical) vapordeposition method, sol-gel method doesn’t need expensive equipment, raw materials and iseasy to control, therefore, has a wide application prospect.The comprehensive study reported by a large number of experiments is to explore apreparation method of homogeneous, transparent and stable of composite sol. By spincoating techniques, Al2O3-CeO2-Y2O3nanocomposite coatings were prepared on SS304substrate. This paper mainly discussed a series of factors which influenced the coatingsquality and property during the preparation process of coatings:(1) Preparation ofprecursor sol. Combined with single factor experiment and orthogonal experiment, theoptimal parameter combination was determined;(2) Spin coating process. Including thedetermination of spin speed and time;(3) Annealing temperature. Including low and highsintering temperature of heat treatment. Corrosion resistance of nanocomposite coatingswas evaluated by weight loss and electrochemical techniques. The morphology,compositions and crystal structures of nanocomposite coating were analyzed by scanningelectron microscopy, energy spectrum and X-ray diffractometer, respectively. Thecorrosion resistance of the uncoated sample, the simplex sample and the optimizedcomposite coating was compared comprehensively.Studies show that the optimal process conditions for precursor solution:0.5~0.6MAl(NO3)3·9H2O, peptization temperature85℃, n(H+)/n(Al3+)=0.25~0.30, peptization time 2h. The best parameter combination of nanocomposite coatings: metal ions totalconcentration of0.533M, percentage of (Ce+Y)/Al of3.75%, PVP concentration of0.4M,spin speed in3000r/min, time30s, spinning5times could obtain coating thickness. Whenthe drying temperature was300℃, and sintering at800℃for2h, Al2O3-CeO2-Y2O3nanocomposite coating with excellent morphology, structure and corrosion resistantperformance could be obtained. The corrosion rate of orthogonal optimal compositecoating is0.0289g/m2h and corrosion current density is2.3605x10-8A/cm2. At the sametime, the impedance value is up to324800Ω·cm2. Compared to the single coating anduncoated sample, the corrosion rate increase nearly34and82times, respectively. Thesingle coating specimen has a crack existed, but the optimum composite coating isrelatively dense, homogeneous and smooth. The thickness of the composite coating isabout2~3μm. Besides, the composite coating phase is mainly composed of γ-Al2O3, Y2O3and CeO2.