Dissertation > Excellent graduate degree dissertation topics show

Studies on the Deterioration Process of Sintered Zinc-aluminum Coating and Composite Coating

Author: WangJun
Tutor: WangJia
School: Ocean University of China
Course: Applied Chemistry
Keywords: sintered zinc-aluminum coating organic top technology composite coating artificial defect electrochemical impedance spectroscopy
CLC: TG174.4
Type: Master's thesis
Year: 2009
Downloads: 171
Quote: 3
Read: Download Dissertation

Abstract


Sintered zinc-aluminum coating, which developed rapidly since it has been originated, is widely used for steel fastener against corrosion. It provides corrosion protection with features such as barrier protection, chromate passivating and sacrificial protection. In marine corrosion environment, the coating anticorrosion is effected by its weak waterproof and inevitable defect during application.In this paper the preparation process, the formation mechanism, the corrosion resistance mechanism of sintered zinc-aluminum coating and the study methods of coating failure process are introduced. The samples of sintered zinc-aluminum coating on steel substrate are prepared with artificial defect in different width. The anticorrosion performances of perfect and defected coatings are characterized by neutral salt spray test, dip immersion and wet-dry cyclic tests in seawater. The results show that the anticorrosion performance is few affected when the defect is less than 1mm, but the coating exhibits bad anticorrosion performance when the defect is larger than 3mm.The deterioration processes of the sintered zinc-aluminum coating are studied by polarization curves, electrochemical impedance spectroscopy and scanning vibrating electrode techniques. The results show that passivation range of defected coating is shorter than that of the perfect. The corrosion current increases and the polarized resistance decreases while the defect width increases. Both of the perfect coating and the defected one are mainly exhibit cathodic protection lasting a long period. The electrochemistry corrosion easily reacts with the defect width increase. The results of SVET show that the coating represents self-healing function for the defect.Composite coating was prepared by adhereed the epoxy Al-rich coating on sintered zinc-aluminum coating. The composite coating is more compact than the sintered zinc-aluminum coating by scanning electron microscope (SEM). The composite coating thickness is only 5μm thicker than that of the sintered zinc-aluminum coating. The composite coating adhesion, tested by cross cut test, is little higher than that of the sintered zinc-aluminum coating. The anticorrosion performances of composite coating are much better than that of the sintered zinc-aluminum coating. The composite coating can endure more than 2880 hours during salt spray test, more than 120 days during dip immersion test and more than 182 wet-dry cycles during wet-dry cyclic test. The potential variety of the composite coating during dip immersion and wet-dry cyclic tests is more stable than that of the sintered zinc-aluminum coating. The epoxy Al-rich coating can decrease the corrosion current and increase the polarized resistance of the coating. A typical Warburg impedance character progressively appears at the initial stage; Al flakes of the epoxy Al-rich coating exhibit cathodic protection with the immersion time.The samples of composite coating are prepared with artificial defect about 0.1 mm and 1 mm. The anticorrosion performances of the defected coating are characterized by neutral salt spray test, dip immersion and wet-dry cyclic test in seawater. The results show that the anticorrosion performance of the 0.1 mm defected coating is much higher than that of the 1 mm defected coating. The defected coating obviously exhibits passivation with the increase of potential. The steel is protected by the coating which provides cathodic protection.The anticorrosion tests results of the defected coating show that composite coating exhibits more sensitive to defect than the sintered zinc-aluminum coating. The composite coating exhibits well anticorrosion while the defect is very minute. The anticorrosion of the composite coating decrease rapidly with the increase of defect width.In conclusion, the sintered zinc-aluminum coating can exhibit high anticorrosion performance, while the defect confined certain range. Those provide foundation for the application of sintered zinc-aluminum coating in marine environment. The organic top coating technique affords new method for the application of sintered zinc-aluminum coating in seawater. It should notice that composite coating is more sensitive to defect than that of sintered zinc-aluminum coating.

Related Dissertations

  1. Electrochemical Studies on Interaction between ApoCopC、BSA and Cu(Ⅱ)、Cu(Ⅰ)、Cd(Ⅱ)、Ag(Ⅰ),O646
  2. The Study of Microstructure and Performance of La2 O3+CeO2-Ni-WC Composite Coating by Vacuum Fusion Sintering,TG174.44
  3. Study of Microbial Corrosion in Central Air-conditioning Cooling Water System,TU831.4
  4. Thermal oxidation protective coating spray preparation and protection mechanisms,TG174.442
  5. Containing artificial defects C_f / Al composites Compression Failure Behavior,TG115.53
  6. Microstructure and Property of Nano Ni-P-Al2O3 Electroless Plating Layer Treated by Laser Technology,TG174.4
  7. Study on Process and Properties of Ni-P-Nano TiO2 Composite Coating on Magnesium Alloy,TG174.44
  8. Studies on Anti-Corrosion Behaviors of Electroless Deposited Ni-P and Ni-P-PTFE Coatings in Seawater,TQ153.1
  9. Copper surface metal clips embedded ceramic composite coating technology research,TG174.44
  10. Sc-containing high strength Al-Zn-Mg-Cu-Zr alloys and corrosion behavior of homogenization,TG146.21
  11. Study on the Ceramic-metal Composite Coatings on the Surface of Carbon Steel by Laser Cladding,TG174.44
  12. Fabrication and Biocharacter of Composite Coating on Mg-Zn Based Alloy,TG174.4
  13. Study on Forming Mechanism of the Fe-Al2O3-FeAl2O4 Composite Coating by Reactive Plasma Spraying,TG174.442
  14. Electrodeposition of Fe-ni Alloy Foil,TQ153.2
  15. Preparation and Catalytic Activity of Electrode Materials for Water Electrolysis,TQ116.2
  16. Studies on the Preparation Process and Protective Properties of the Cold Spray Copper Alloy Coatings,TG174.44
  17. Research on Surface Modification of Power Station Valve Steel,TG174.44
  18. Study of Composite Coating by Arc Spraying Feeding Ceramic Powders from Outside,TG174.453
  19. Study on FE-Al Composite Coatings in Laser Cladding and Numerical Simulation,TG174.44
  20. Electrochemical Corrosion Characteristic of Direct Current Pulsed Plasma Sourse Nion AISI 304 Stainless Steel,TG156.82
  21. Titanium alloy surface laser in situ microscopic structure and mechanical properties of synthesis of TiN/Ti_3Al coating,TG174.4

CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology
© 2012 www.DissertationTopic.Net  Mobile