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Outline Curriculum (5 lectures) Each lecture 45 minutes Lecture 1: An introduction in electrochemical coating Lecture 2: Electrodeposition of coating Lecture.

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Presentation on theme: "Outline Curriculum (5 lectures) Each lecture 45 minutes Lecture 1: An introduction in electrochemical coating Lecture 2: Electrodeposition of coating Lecture."— Presentation transcript:

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 5 An 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: 1.Improved corrosion resistance. 2.Improved wear resistance. 3.Longer lifetime. 4.Aesthetic surface finish.

13 Optical micrograph of 21 m PEO coating on Mg alloy:

14 Optical micrograph of 12 m PEO coating on Mg alloy:

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

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

17 Electrochemical anodizing Transformation of Ti foil to TiO 2 nanotubes Anodizing e.g V Electrochemical formation of oxide Ti + 2H 2 O TiO 2 + 4H + + 4e - Chemical dissolution of oxide TiO 2 + 6F - + 4H + TiF H 2 O Competing reactions for the formation of TiO 2 nanotubes

18 Green electrolyte, CH 3 SO 3 H Anodizing of TiO 2 nanotubes from Ti foil 200 nm 100 nm

19 Surface microstructure Nanotubes Au-TiO 2 vertically aligned array 1 m 100 nm

20 20 Reflective nanocrystalline PbO 2 Application: Solar heat absorber

21 Rotating Cylinder Reactor High throughput electrodeposition Cu-Sn alloys

22

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

24 TEM image Nanotubes TiO 2 in a nickel matrix Nanotubes TiO 2 Nickel matrix 100 nm 20 nm

25 25 Electrodeposition of polypyrrole 1.0 cm Stainless steel substrate Polypyrrole

26 26 Electrocatalysts for H 2 O electrolysis Nanocrystalline and amorphous Ni-Co alloys 0g Co2 g10 g20 g40 g60 g80 g100 g150 g200 g Co content in alloyed electrocatalyst increases More effective electrocatalyst to evolution oxygen 100g Ni 1.0 cm

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

28 28 Multilayered - and -PbO 2 α- and β-PbO 2 β-PbO 2

29 29 Thin film lead-acid battery Nanosized materials 100 nm Nanosized material PbO 2 + PbSO 4

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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