Dissertation > Excellent graduate degree dissertation topics show

Corrosion Behavior of Pure Zinc under a Combined Electrolyte Layer of an Open Layer and a Confined One

Author: SunHaiFeng
Tutor: AnBaiGang
School: Liaoning University of Science and Technology
Course: Applied Chemistry
Keywords: Corrosion Zinc Open electrolyte layer Confined electrolyte layer Epoxy coating
CLC: TG172
Type: Master's thesis
Year: 2012
Downloads: 16
Quote: 0
Read: Download Dissertation

Abstract


The nature of atmospheric corrosion is an electrochemical process occurred underthin layer of electrolyte. Recent years, the study on atmospheric of metal is focused onthe micro-environment that metal suffered corrosion, such as the shape of thinelectrolyte layer, droplet size and shape, and the forms of electrolyte layer, etc,. Mostmetal used in atmosphere are protected by using organic coating to inhibit atmosphericcorrosion. However, the coating is inevitable to be locally broken so that the metalsubstrate is directly exposed to atmosphere. In this case, the electrolyte layer combinedan open layer with a confined one can be formed around the area of broken coating. Sofar, there is few study on the atmospheric corrosion of metal under this kind ofcombined layer of electrolyte.As important metal materials,50%of zinc production per year is used as thesacrifice anode coating for steel, and zinc coating is generally coated with an organiccoating, especially in automobile industry and constructing business. Therefore, thecombined layer of electrolyte become the one of environment that zinc often suffercorrosion. In this dissertation, by using a electrochemical cell that can simulate thecombined layer of electrolyte, corrosion behavior of zinc under the combined layerformed by3wt%NaCl solution, the effects of concentration of Na2SO4solution oncorrosion of zinc under the combined layer were studied. The corrosion behavior of zincunder epoxy coating was also investigated by using an epoxy coating/zinc electrodesystem. The result are as follow:（1） Under the combined layer formed by3wt%NaCl solution, corrosion potential ofzinc under the confined layer is always more negative than the zinc under the open layerin the electrolyte thickness range of50μm-410μm, and this difference in corrosionpotential increases with decreasing the thickness of electrolyte layer, which results agalvanic corrosion cell where the confined zinc plays as anode but the open zinc ascathode. The corrosion rate of confined zinc is obviously higher than the open zinc dueto the galvanic cell and acidification of confined layer caused by hydrolysis of excessivezinc ions. The critical thickness of zinc corrosion under the combined layer is105μm, atwhich corrosion rate of zinc reaches the maximum.（2） Under the combined layer of electrolyte with the thickness of100Na2SO4, theeffect of concentration of Na2SO4on corrosion rate of confined zinc and open zinc isdifferent.Because the transport of oxygen and ions is inhibited by the confined layer ofelectrolyte, the concentration increase of electrolyte enhances the conductivity ofconfined layer, hence corrosion rate of confined zinc increase with the concentration ofNa2SO（40.01M-0.2M）. corrosion rate of confined zinc is mainly affected by solubilityand ion conductivity of electrolyte, and thus reaches the maximum when theconcentration of Na2SO4is0.1M. （3） Accelerated corrosion test of epoxy coating/zinc system under the combined layerof200μm formed by3wt%NaCl solution showed that, in initial period of corrosion ofzinc under coating corrosion products formed hindered the electrolyte diffusion to thesurface of metal, hence corrosion rate of zinc decreased with accelerated test time. Inmiddle period, the stress caused by accumulation of products resulted the degradation ofcoating and thus corrosion rate of zinc increased with test time. In the latest period,because the protective ability of coating on zinc matrix lost completely, the protectivecorrosion products resulted that corrosion rate of zinc decreased gradually withaccelerated test time.

Related Dissertations

  1. Research on Geological Features of Yinchanggou-Qiluogou Lead-Zinc Ore Deposit, Ningnan County, Sichuan Province,P618.4
  2. Anti-corrosion Property of Flake Zinc Epoxy Coating Doped with Rare Earth in SRB,TQ630.1
  3. Effects of Different Applying Methods of Copper and Zinc and AM Fungi under Different P-Applied Levels on Growth and Tanshinones of Salviae Miltiorrhizae Bunge,S567.53
  4. Effects of Copper, Zinc and Selenium on Yield and Quality of Chrysanthemum Morifolium Ramat,S567.239
  5. Study on Screening of Bacterial Quorum Sensing from Plant Extraction and Their Inhibitions on Biofilm Formation,Q93
  6. Research on Caster Oil-based Cold Rolling Oil,TE666
  7. Study on the in Vitro Effect of Zinc on the Growth of Murine Embryonic Palatal,R782.2
  8. Northwest Geological two lead and zinc in the river Construction of QHSE management system,X936;X322
  9. Inorganic and inorganic - organic hybrid Zn -based catalysts and catalytic L- lactide ring-opening polymerization of L- polylactic acid applied research,O631.3
  10. Research on High Aluminum Zinc-Based Alloy Tyre Valves,U463.341
  11. Surface Modification of Al-alloy for Improving Bonding Strength with Pps and the Corrosion Resistance of Al-alloy,TG174.4
  12. Research on the Morphology and Fractal Growth of Electrolytic Zinc for Zinc-Air Fuel Cells,TM911.41
  13. Fluorescent Sensor Based on 1,10-Phenanthroline Groups,TP212.2
  14. Technology Research on Preparation of Nanometer ZnO by Hot Galvanizing Dross,TB383.1
  15. The Experimental Investigation of Stress Corrosion for 34CrMo4 Alloy Steels in Wet H2S Environment,TG172.9
  16. The Statistics and Analysis for Defects of In-service Sphere Tank,TQ053.2
  17. Preparation of AgI-ZnO Nanocomposites and Their Properties,TB383.1
  18. Study on Microstructure and Performance of Laser Cladding Ni-Based Amorphous Alloy Coatings,TG174.4
  19. Research on Preparation of Dopamine Composite Films on Stainlees Steel and Corrosion Resistance,TG174.44
  20. The Experimental Research on Reliable Service Life of Toothed Gearing,TH132.41
  21. Preparation and Properties of Reactive Thermal Sprayed Ternary Boride Cermet Coatings,TG174.4

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