UTILIZATION OF ELECTRICAL ENERGY AND TRACTION. process of electro-deposition-clearing, operation, deposition of metals, polishing and buffing. PREPARED BY: JOBIN ABRAHAM.

1. UTILIZATION OF ELECTRICAL
ENERGY AND TRACTION
[2160907]
ACTIVE LEARNING ASSIGNMENT :
TOPIC : PROCESS OF ELECTRO-DEPOSITION-CLEARING, OPERATION,
DEPOSITION OF METALS, POLISHING AND BUFFING.
UNIVERSITY : GUJARAT TECHNOLOGICAL UNIVERSITY.
COLLEGE : VADODARA INSTITUTE OF ENGINEERING.
DEPARTMENT : ELECTRICAL ENGINEERING [E.E.– I].
SEMESTER : VI.
PREPERED BY :
130800109025 [ MEET K. JANI ]
130800109026 [ BHARGAV M. JAYSWAL ]
130800109027 [ JESTY JOSE ]
130800109028 [ JOBIN ABRAHAM ]
GUIDED BY : ASST. PROF. PRAGNESH N. PRAJAPATI.
[ELECTRICAL DEPARTMENT]
ACTIVE LEARNING ASSIGNMENT
1

2.  Contents:
 Introduction
 Process of electro-deposition
 Electro-deposition-clearing
 Depositioning of alloys
 Electro-polishing or electro-buffering
 References
ACTIVE LEARNING ASSIGNMENT 2

3.  Introduction:
 Electroplating is a process that uses
electric current to reduce dissolved metal cations so that they form a
coherent metal coating on an electrode.
 The process used in electroplating is called electro-deposition.
 It is analogous to a galvanic cell acting in reverse.
 The part to be plated is the cathode of the circuit. In one technique,
the anode is made of the metal to be plated on the part.
 Both components are immersed in a solution called
an electrolyte containing one or more dissolved metal salts as well as
other ions that permit the flow of electricity.
 A power supply supplies a direct current to the anode, oxidizing the
metal atoms that it comprises and allowing them to dissolve in the
solution.
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4.  Introduction {cont.}:
 At the cathode, the dissolved metal ions in the electrolyte solution
are reduced at the interface between the solution and the cathode,
such that they "plate out" onto the cathode.
 The rate at which the anode is dissolved is equal to the rate at which
the cathode is plated, i.e. the current through the circuit.
 In this manner, the ions in the electrolyte bath are continuously
replenished by the anode.
 Other electroplating processes may use a non-consumable anode such
as lead or carbon.
 In these techniques, ions of the metal to be plated must be
periodically replenished in the bath as they are drawn out of the
solution.
 The most common form of electroplating is used for creating coins
such as pennies, which are small zinc plates covered in a layer
of copper.
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5.  Process of electro-deposition:
 The cations associate with the anions in the solution. These cations
are reduced at the cathode to deposit in the metallic, zero valence
state.
 For example, in an acid solution, copper is oxidized at the anode to
Cu2+ by losing two electrons.
 The Cu2+associates with the anion SO4
2− in the solution to form
copper sulfate. At the cathode, the Cu2+ is reduced to metallic copper
by gaining two electrons.
 The result is the effective transfer of copper from the anode source
to a plate covering the cathode.
 The plating is most commonly a single metallic element, not an alloy.
However, some alloys can be electrodeposited,
notably brass and solder.
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6.  Process of electro-deposition {cont.}:
 Many plating baths include cyanides of other metals (e.g., potassium
cyanide) in addition to cyanides of the metal to be deposited.
 These free cyanides facilitate anode corrosion, help to maintain a
constant metal ion level and contribute to conductivity.
 Additionally, non-metal chemicals such as carbonates and phosphates
may be added to increase conductivity.
 When plating is not desired on certain areas of the substrate, stop-
offs are applied to prevent the bath from coming in contact with the
substrate.
 Typical stop-offs include tape, foil, lacquers, and waxes.
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7.  Application of electro-deposition :
 Since its invention in 1805 by Italian chemist, Luigi Brugnatelli,
electroplating has become an extensively used industry coating
technology. Its applications are mainly in the following four groups:
 Decoration:
 Coating a more expensive metal onto a base metal surface in
order to improve the appearance. Applications are jewellery,
furniture fittings, builders’ hardware and tableware.
 Protection:
 Corrosion-resistant coatings such as chromium plating of
automobile parts and domestic appliances, zinc and cadmium
plating of nuts, screws and electrical components. Wear-resistant
coatings such as nickel or chromium plating of bearing surfaces
and worn shafts and journals.
 Electroforming:
 Manufacture of sieves, screens, dry shaver heads, record
stampers, moulds, and dies.
 Enhancement:
 coatings with improved electrical and thermal conductivity,
solderability, reflectivity etc.
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8.  Electro-deposition-clearing:
 Cleanliness is essential to successful electroplating, since molecular
layers of oil can prevent adhesion of the coating.
 ASTMB322 is a standard guide for cleaning metals prior to
electroplating.
 Cleaning processes include solvent cleaning, hot alkaline detergent
cleaning, electro-cleaning, and acid treatment etc.
 The most common industrial test for cleanliness is the water break
test, in which the surface is thoroughly rinsed and held vertical.
 Hydrophobic contaminants such as oils cause the water to bead and
break up, allowing the water to drain rapidly.
 Perfectly clean metal surfaces are hydrophilic and will retain an
unbroken sheet of water that does not bead up or drain off.
 ASTM F22 describes a version of this test. This test does not detect
hydrophilic contaminants, but the electroplating process can displace
these easily since the solutions are water-based.
 Surfactants such as soap reduce the sensitivity of the test and must
be thoroughly rinsed off.
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9.  Deposition of alloys:
 It is possible to deposit alloys also provided the electrode potentials
of the constituent metals are not much different.
 Electroplating of brass and bronze are the best examples.
 For this, the anode is made up of an alloy to be deposited and the
electrolyte consists of a mixture of electrolytes and which would
have been employed for separate deposition of metal consumed.
 For brass plating solution of double cyanides of zinc and potassium
and copper and potassium is used as electrolyte and current density
of 25 – 40 Ampere/ square meter is used.
ACTIVE LEARNING ASSIGNMENT 9

10.  Electro-polishing or electro-buffering :
 Electro-polishing, also known as electrochemical
polishing or electrolytic polishing (especially in the metallography
field) or electro-buffering, is an electrochemical process that
removes material from a metallic work piece.
 It is used to polish, passivate, and deburr metal parts. This process
basically makes the surface smoother.
 It may be used in lieu of abrasive fine polishing in
microstructural preparation.
ACTIVE LEARNING ASSIGNMENT 10

11.  Electro-polishing {cont.}:
 Typically, the work piece is immersed in a temperature-controlled
bath of electrolyte and serves as the anode; it is connected to the
positive terminal of a DC power supply, the negative terminal being
attached to the cathode.
 A current passes from the anode, where metal on the surface is
oxidized and dissolved in the electrolyte, to the cathode.
 At the cathode, a reduction reaction occurs, which normally produces
hydrogen.
 Electrolytes used for electro-polishing are most often concentrated
acid solutions having a high viscosity, such as mixtures of sulfuric
acid and phosphoric acid.
 Other electro-polishing electrolytes reported in the literature include
mixtures of perchlorates with acetic anhydride and methanolic
solutions of sulfuric acid.
 To achieve electro-polishing of a rough surface, the protruding parts
of a surface profile must dissolve faster than the recesses.
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12.  Electro-polishing {cont.}:
 This process, referred to as anodic leveling, is achieved by a mass
transport limited dissolution reaction.
 Anodic dissolution under electro-polishing conditions deburrs metal
objects due to increased current density on corners and burrs.
 Most importantly, successful electro-polishing should operate under
diffusion limited constant current plateau, achieved by following
current dependence on voltage (polarization curve), under constant
temperature and stirring conditions.
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13.  Applications of electro-polishing:
 Electro-polishing has many applications in the metal finishing industry
because of its simplicity and it can be applied to objects of complex
shape.
 Typical examples are electro-polished stainless steel drums of
washing machines and stainless steel surgical devices.
 Electro-polishing is also commonly applied to the preparation of thin
metal samples for transmission electron microscopy because electro-
polishing does not cause mechanical deformation of surface layers
usually observed when mechanical polishing is used.
 Ultra high vacuum (UHV) components are typically electro-polished in
order to have a smoother surface for improved vacuum pressures,
outgassing rates, and pumping speed.
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14.  References:
1. S. Sivanagaraju, M. Balasubba, D. Srilatha “Electric Energy -
Generation, Utilization and Conservation”, PEARSON Education,
Inc., Fifth Impression, 2012, ISBN : 978-81-317-6774-0.
2. J.B. Gupta “Utilization of Electric Power and Electric Traction”,
S.K. KATARIA & SONS PUBLISHERS, Tenth Edition, 2015 Reprint,
ISBN : 978-93-5014-258-5.
3. https://en.wikipedia.org/wiki/Electroplating
4. https://en.wikipedia.org/wiki/Electropolishing
5. http://coursenotes.mcmaster.ca/4L04/Thin_Films/Electrodepositio
n_of_Metal.pdf
6. Video of electroplating : https://youtu.be/TulCpgLF594
7. Video of electro-polishing : https://youtu.be/0XUS9bRSihM
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15. ANY QUESTIONS?
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