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Outline Curriculum (5 lectures) Each lecture  45 minutes

Outline Curriculum (5 lectures) Each lecture  45 minutes. Lecture 1: An introduction in electrochemical coating Lecture 2: Electrodeposition of coating Lecture 3: Anodizing of valve metal Lecture 4: Electroless deposition of coating Lecture 5: Revision in electrochemical coating.

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Outline Curriculum (5 lectures) Each lecture  45 minutes

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  1. Outline Curriculum (5 lectures)Each lecture  45 minutes Lecture 1: An introduction in electrochemical coating Lecture 2: Electrodeposition of coating Lecture 3: Anodizing of valve metal Lecture 4: Electroless deposition of coating Lecture 5: Revision in electrochemical coating

  2. Lecture 1 of 5An Introduction In Electrochemical Coating

  3. Electrochemical Surface Engineering(Electrochemical Coating) • Is it about the deposition a coating onto surface, via electrochemical reactions. • The coating can be (a) metallic, (b) metal oxide or (c) conductive polymer. • Metallic coating: Electroplating • Metal oxide, conductive polymer: Anodizing • Electroless deposition

  4. Electrochemical Surface Engineering • An electro-chemical reaction • Cathode: Metals/alloys coating • Anode: Metal oxides • Conductive solution: ionic species • Transfer of electrons

  5. Electroplating of copper

  6. Anodizing • An electrolytic passivation process. • To form a thick oxide layer on a metal. • Metal oxide forms on the anode.

  7. Electroless deposition • Electroplating: consisting of two electrodes, electrolyte, and external source of current. • Electroless deposition: this process uses only one electrode and no external source of electric current. • Electroless deposition: the solution needs to contain a reducing agent so that the reaction can proceed: • Metal ion + Reduction solution  Metal solid + oxidation solution Catalytic surface

  8. Definition: Electron transfer reactions • Oxidizing agent + n e- = Reducing agent • Oxidizing agents get reduced • Reducing agents get oxidized • Oxidation is a loss of electrons (OIL) • Reduction is a gain of electrons (RIG) OILRIG

  9. Industrial scale anodizing of Aluminium

  10. Example of anodizing

  11. Brush electroplating of gold onto stainless steel substrate

  12. Tin-Zinc coating onto steel substrate • Benefits of electroplated • metallic surfaces: • Improved corrosion resistance. • Improved wear resistance. • Longer lifetime. • Aesthetic surface finish.

  13. Optical micrograph of 21 mm PEO coating on Mg alloy:

  14. Optical micrograph of 12 mm PEO coating on Mg alloy:

  15. Porosity in electroless Ni-P deposits (<5 mm) on mild steel

  16. Log-log Porosity vs. thickness for electroless Ni-P deposits on steel

  17. Electrochemical formation of oxide Ti + 2H2O → TiO2 + 4H+ + 4e- Chemical dissolution of oxide TiO2 + 6F- + 4H+ → TiF62- + 2H2O Competing reactions for the formation of TiO2 nanotubes Electrochemical anodizingTransformation of Ti foil to TiO2 nanotubes Anodizing e.g. 10-100 V

  18. Green electrolyte, CH3SO3HAnodizing of TiO2 nanotubes from Ti foil 100 nm 100 nm 200 nm 200 nm

  19. Surface microstructureNanotubes Au-TiO2 vertically aligned array 100 nm 1 m 100 nm

  20. Reflective nanocrystalline PbO2Application: Solar heat absorber 20

  21. Rotating Cylinder ReactorHigh throughput electrodeposition Cu-Sn alloys

  22. Rotating Cylinder ReactorHigh throughput electrodeposition Cu-Sn alloys

  23. Nanoparticles SiC in a nickel matrixWear resistance coating Darker contrast: nanoparticle SiC 100 nm Ni-SiC coating Copper substrate 200 m

  24. TEM imageNanotubes TiO2 in a nickel matrix Nanotubes TiO2 20 nm Nickel matrix 100 nm

  25. Electrodeposition of polypyrrole Stainless steel substrate Polypyrrole 1.0 cm 1.0 cm 25

  26. Electrocatalysts for H2O electrolysis Nanocrystalline and amorphous Ni-Co alloys 0g Co 2 g 10 g 20 g 40 g 60 g 80 g 100 g 150 g 200 g 100g Ni 1.0 cm Co content in alloyed electrocatalyst increases More effective electrocatalyst to evolution oxygen 26

  27. Large scale electrodepositionThick film, multilayered Ni-Co on Fe substrate 200 μm Ni Ni Co Fe Each tank = 5 Litres 20 cm

  28. Multilayered - and -PbO2 α- and β-PbO2 β-PbO2 28

  29. Thin film lead-acid batteryNanosized materials Nanosized material PbO2 + PbSO4 100 nm 29

  30. Summary • Electrochemical coatings range from nanoparticles of metal on nanostructured, inorganic supports through to hard <100 mm Cr coatings on steel. • Applications include catalysts, fuel cell-, solar cell- and battery electrodes together with tribological/corrosion resistant coatings for electronic materials, transport and heavy engineering. • Plasma electrolytic oxidation uses the application of a high a.c. voltage to produce a hard, wear resistant oxide coating on light metals (such as Mg alloys) for automotive, aerospace and leisure. • Electroless Ni deposits (typically <20 mm in thickness) on steel or Al alloys are widely used in engineering applications for their corrosion and wear resistance. Thin coatings tend to have high porosity.

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