Thermodynamics and Kinetics of Corrosion Flashcards
(56 cards)
the term used to describe this
reduction, denoted as ΔG (G decreases along with the reaction
time)
Reaction affinity
is a quantitative measure
of a chemical reaction’s tendency to start, which includes the reaction of a
metallic material with its environment.
Gibbs free energy change (ΔG)
It is also a direct measure of the work capacity or the maximum electric
energy possible that is available from a system
Gibbs free energy change (ΔG)
the change in free energy can be classified as a ____________function and is__________ of the reaction path.
state; independent
can be defined as a product of charges moved (Q) and the
electrochemical potential (E) through which it is moved
electrical work
in the
case of electrochemical cells and the charge is represented as 1 mol of
reactant in which n mol of electrons are transferred, the electrical work
done by the cell is quantified
-nE
which are crucial part of the corrosion process, can be
used to express the tendency of a metal to corrode
emf
for any type of cell means there is also a higher
tendency for the overall chemical reaction of the cell to proceed, which is
applicable to any type of cell
higher value of E
the standard free energy of the cell reaction,
ΔG° is directly related to the standard cell potential difference across the
cell, wherein
G= -nFE
____________ value of ΔG results in a larger tendency to make the reaction proceed
more negative
__________value of ΔG° (the reactants and products
are in their standard states) signifies an obvious likelihood for magnesium
to react with water and oxygen
large significant negative
For a reaction to take place, the driving voltage must be _
positive
On the other hand, when the initial and final Gibbs free energy are the
same (ΔG = 0) or when there is a negative driving voltage (ΔG > 0),
there is enough reason to conclude that a reaction might
not occur
when __________, it is said that the reaction is said to be in an equilibrium
state
ΔG = 0
When _____________, it is said that the system is more likely to change
in the other direction to that stated, unless the external energy of the
system is affected by external forces.
ΔG > 0
For dissolved species, ______________ which includes the effects of the system
’
s
environment
activity coefficient
In case of gaseous species, __________ includes the effects of the system’s environment
fugacity coefficient
Furthermore, the tendency of a material to corrode is ____________
of reaction rate
not a direct measure
It is not always true that a _____________ of ΔG will result in a higher corrosion rate
large negative value
a _______________
always indicates that a reaction will not proceed under certain
conditions
positive value of ΔG
The standard conditions for solid, liquid compounds, and even elements is
the pure compound or element
The standard conditions for gases is set at
P = 100kPa
C = 1M
The equilibrium electrodes are also termed
Half cells
If these electrodes are maintained at
equilibrium conditions, they are now called
standard half-cells
