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Corrosion Engineering > ELECTROCHEMISTRY AND CORROSION > Flashcards

ELECTROCHEMISTRY AND CORROSION Flashcards

1
Q

USUALLY DEFINED
AS THE DEGRADATION OF METALS
DUE TO AN ELECTROCHEMICAL
PROCESS

A

corrosion

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2
Q

One in which electricity is
produced by a chemical reaction.

A

electrochemical process

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3
Q

a chemical reaction
involving the transfer of electrons
between two electrodes in an
electrochemical cell

A

electrochemical process

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4
Q

These are also called Galvanic cells or simply
Voltaic cells

A

electrochemical cell

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5
Q

s a device that converts
chemical energy produced in a redox reaction
into electrical energy

A

electrochemical cell

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6
Q

Electrochemical cells are a combination of two electrical conductors known as _________ immersed in an __________

A

electrode, electrolyte

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7
Q

he galvanic cell is named after

A

Luigi Galvani

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8
Q

EChemical cell is composed of two compartments or

A

half cells

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9
Q

On _______________, positive current flows through the metallic path
from positive electrode to negative electrode.

A

short-circuiting

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10
Q

the gain of electrons or a
decrease in oxidation state by a
molecule, atom, or ion

A

reduction

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11
Q

the loss of electrons or an
increase in oxidation state by a
molecule, atom, or ion

A

oxidation

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12
Q

device used in an
electrochemical cell for connecting
its oxidation and reduction half
cells wherein an inert electrolyte is
used.

A

salt bridge

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13
Q

junction that connects the
anodic and cathodic
compartments in a cell or
electrolytic solution

A

salt bridge

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14
Q

The more _________ the reduction potential, the more these elements
want to attract electrons
towards them.

A

positive

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15
Q

The energy conversion is
achieved by __________ redox reactions, producing a
flow of electrons in electrochemical cells.

A

spontaneous (ΔG <0)

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16
Q

In __________, electrical energy is used to drive
a non-spontaneous (ΔG ≥ 0)
chemical reaction (redox
reactions)

A

electrolytic cell

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17
Q

Types of electrochemical cells

A

Dissimilar Electrode Cell
Concentration Cell
Differential Temperature Cell

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18
Q

These cells involve
different types of metals
or metal compositions
coming into contact,
leading to electron
transfer between them.

A

Dissimilar Electrode Cell

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19
Q

Types of concentration cells

A

Salt concentration
Differential aeration

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20
Q

These are cells with two identical
electrodes, each in contact with a
solution of different composition.

A

Salt concentration cell

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21
Q

Occurs due to differences in potential
between differently Aerated areas
Part of the metal exposed to air is more
oxygenated and acts as a Cathode
Part of the metal immersed in the
electrolyte is poorly oxygenated & acts
as an anode

A

Differential aeration cells

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22
Q

This is the type of cell when
two identical electrodes are
immersed in same
electrolyte, but the electrodes
are immersed into solution of
two different
temperatures

A

Differential temperature cell

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23
Q

The _____________ series s has been established by measuring
the potential of various electrodes versus ____________

A

Electrochemical, standard hydrogen electrode (SHE)

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24
Q

orderly arrangement of the
standard potentials for all metals.

A

Emf Series

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25
Q

The more ________ values correspond to the more reactive metals

A

negative

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26
Q

It arises when two metals with
dissimilar compositions come into
contact in the presence of an
electrolyte.

A

Galvanic cell

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27
Q

Determines the
electrochemical potential and
nobility of metals (and metal
alloys)

A

Galvanic series

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28
Q

Ranking of metals and alloys
according to their free
corrosion potential in a given
electrolyte.

A

Galvanic series

29
Q

THE CLOSER A METAL
OR AN ALLOY IS IN
THE GALVANIC
SERIES, THE __________ ARE
THE EFFECTS OF
GALVANIC
CORROSION
COMPARED TO THOSE
METALS FAR APART.

A

LESS

30
Q

Conditions for Galvanic Corrosion

A
  1. Metals involved must establish electrical connectivity
  2. Metals must maintain ionic connectivity
31
Q

Current is produced when electrons flow (through
anode to cathode)

A

Electrode potentials

32
Q

Types of reference electrode potentials

A

Standard Hydrogen Electrode
Calomel Reference Electrode
Silver-Silver Chloride Reference Electrode
Saturated Copper-Copper Sulfate Reference Electrode

33
Q

Standard Electrode
Potential (E = 0) at
temperature of ______

A

278K

34
Q

The half cell reaction of SHE can be written as follows:

A

2H+ + 2e- <-> H2

35
Q

The reaction for SHE generally takes place on a

A

platinum electrode

36
Q

The pressure of the hydrogen gas present in this half cell for SHE is

A

1 bar

37
Q

Why Platinum is Used?

A
  1. Relatively inert
  2. . Has catalytic qualities
  3. Surface can be platinized platinum electrode
  4. Improve kinetics
38
Q

Reference electrode used in laboratory

A

Calomel reference electrode

39
Q

For CRE, _________ is placed at the
bottom of the tube, which is
covered with a paste of ____________

A

Pure mercury, mercury-mercurous chloride

40
Q

The calomel is only ___________ in potassium chloride solution

A

slightly soluble

41
Q

The half cell reaction of CRE can be written as

A

Hg2Cl2 + 2e- -> 2Hg + 2Cl-

42
Q

The activity of Hg22+,
depends on the _________

A

concentration of KCl

43
Q

Composed of a silver
wire, sometimes
coated with a layer of
solid silver chloride,
immersed in a solution
that is saturated with
potassium chloride
and silver chloride.

A

Silver-Silver Chloride
Reference Electrode

44
Q

When the silver – silver chloride electrode is immersed in a
chloride solution, the following equilibrium is established

A

AgCl + e- -> Ag + Cl-

45
Q

Like the calomel electrode, the potential in Silver-AgCl RE is more active the _____

A

HIGHER the KCl concentration

46
Q

In 0.1 N KCl for Ag-AgCl, the value is ________, and the temperature coefficient is__________

A

0.288 V; -4.3 × 10− 4 V/ ° C.

47
Q

Consists of metallic copper immersed in
saturated copper sulfate.

A

Saturated Copper-Copper
Sulfate Reference Electrode

48
Q

It is used primarily in field measurements where
the electrode must be resistant to shock and where
its usual large size minimizes polarization errors.

A

Saturated Copper-Copper
Sulfate Reference Electrode

49
Q

The electrode’s
precision, though
slightly lower than
that of calomel or
silver chloride
electrodes, is still
sufficient for most
corrosion studies

A

Saturated Copper-Copper
Sulfate Reference Electrode

50
Q

Half cell reaction for Cu-CuSO4

A

Cu2+ + 2e- -> Cu (0.316V, 7E-4)

51
Q

relate the current of an
electrochemical reaction to the
number of moles of the element
being reacted and the number of
moles of electrons involved.

A

Faraday’s empirical laws of
electrolysis

52
Q

The charge carried by 1 mol of electrons
is known as

A

1 faraday (F) = 96,485 C/mol

53
Q

It is the current produced in
an electrochemical cell
during corrosion. It is the
dissolution current at the
corrosion potential.

A

CORROSION
CURRENT

54
Q

It is the speed at which any
given metal deteriorates or
corrodes in a specific
environment

A

CORROSION
RATE

55
Q

provides a way to calculate corrosion
rate.

A

Corrosion current

56
Q

However, corrosion current
alone doesn’t directly tell
you the____________

A

rate of material loss

57
Q

A reduction current that occurs when
electrons flow from the electrode
surface to a species in solution. For
example, oxygen reduction in a fuel cell

A

CATHODIC
CURRENT

58
Q

An oxidation current that occurs when
electrons flow into the electrode from a
species in solution. For example,
hydrogen oxidation in a fuel cell

A

ANODIC
CURRENT

59
Q

The absolute equality between the anodic and cathodic currents
expressed below does not mean that the current densities for these
currents are equal

A

SURFACE AREA EFFECT

60
Q

the effect of a certain amount of anodic current concentrated on a small area of
metal surface will be __________ than when the effect of the same amount of
current is dissipated over a much larger area

A

much greater

61
Q

If Sc/Sa&raquo_space; 1, then __________. If Sc/Sa &laquo_space;1, then ________

A

amplifying factor, stifling factor

62
Q

When polarization occurs
mostly at the cathode, the
corrosion rate is said to be

A

cathodically controlled

63
Q

occurs when the electrolyte
resistance is so high that the
resultant current is not suffi
cient to appreciably polarize
anodes or cathodes

A

Resistance control

64
Q

can be
calculated from the
corrosion potential and the
thermodynamic potential

A

Corrosion current

65
Q

impressed current cathodic
protection (ICCP) or by another
metal that corrodes more readily
than the metal being protected and
therefore is sacrificed is the process

A

THEORY OF
CATHODIC
PROTECTION

66
Q

If the metal is polarized slightly beyond the
open -circuit potential, φA , of the anode, the
corrosion rate remain

A

zero

67
Q

Should the applied current fall
below that required for
complete protection, some
____________________
occurs

A

degree of protection

68
Q
A

Corrosion Engineering (6 decks)

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