Corrosion Flashcards

1
Q

determines whether the reaction is
spontaneous, non-spontaneous or at equilibrium .

A

Gibbs free energy

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1
Q

quantifies the tendency of any
metal’
s to react with its environment.

A

CHANGE OF GIBBS FREE
ENERGY

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2
Q

a simple
“chemical” reaction that can be used to understand how
electrochemical concepts can be applied to predict
corrosion tendency of a metal.

A

Corrosion of iron in an acid

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3
Q

metal atoms lose
electrons and form metal ions

A

Oxidation

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4
Q

non-metallic
substances such as oxygen gain
electron

A

Reduction

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5
Q

overall corrosion reaction can be described in terms of

A

half-reactions

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6
Q

corrosion of metals occurs
within a localized electrochemical
cell

A

corrosion cell.

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7
Q

involves the spatial
separation of anodic and cathodic
areas on the metal surface leading
to formation of corrosion sites.

A

corrosion cell

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8
Q

where oxidation occurs,
leading to the release of metal ions.

A

anode

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9
Q

Reduction reactions take place at
the

A

cathode

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10
Q

serves as a medium
for ion transport

A

electrolyte

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11
Q

the potential difference
measured under standard conditions (1 M concentration, 1 atm
pressure, and a temperature of 25°C) for a half-cell reaction
relative to the SHE.

A

standard electrode potential

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12
Q

quantifies the tendency of a metal to undergo
oxidation or reduction relative to a standard reference electrode

A

standard electrode potential

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13
Q

historically important electrode. It is the halfcell in which hydrogen gas is bubbled over a
platinum electrode immersed in a solution having
a known concentration of hydrogen ions

A

STANDARD HYDROGEN ELECTRODE

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14
Q

On coupling
one of them turns into anodic and the other cathodic such that
the cell potential becomes positive.

A

ELECTRO MOTIVE
FORCE (EMF) SERIES

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15
Q

Hydrogen equilibrium bears

A

zero value

16
Q

most negative or
active half-cell tends to be

17
Q

most
positive or noble half-cell tends to be

18
Q

Relations between the energy and the potential of a cell

A

NERNST EQUATION

19
Q

outline regions of
active corrosion, oxides/hydroxides
formation, and thermodynamic immunity
for a metal

A

Potential-pH diagrams/Pourbaix diagrams

20
Q

If the oxides/hydroxides protect the underlying metal, then
this region

A

passive region

21
Q

Thermodynamically immune region ensures complete
prevention of metal from corrosio

A

anodic protection and cathodic protection

22
Q

control the cathodic and
anodic currents that are integral components of
corrosion processes

A

polarization effects

23
Q

deviation in
the potential (voltage) of an electrode from its
equilibrium

A

Overpotential

24
quired to initiate the electrochemical reaction at the electrode surface.
activation energy
25
Activation polarization is due to
retarding factors
26
most important variable that explains the large differences in the rate of hydrogen production on metallic surfaces.
exchange current density
27
often added to power cells such as the popular alkaline primary cells to stifle the thermodynamically favored production of gaseous hydrogen and prevent unpleasant incidents
Mercury
28
provide power in a highly acidic environment in a relatively safe manner unless excessive charging currents are used.
lead acid battery
29
arises from the variation in ion concentrations at the electrode interface
CONCENTRATION POLARIZATION
30
related to the mass transport limitations of reactants or products to or from the electrode surface.
CONCENTRATION POLARIZATION
31
When a chemical species participating in a corrosion process is in short supply, the mass transport of that species to the corroding surface can
become rate limiting
32
Mass transport to a surface is governed by three forces, that is
diffusion, migration, and convection.
33
The flux of a species O to a surface from the bulk is described with
Fick’s first law.
34