3 - Electrochemistry and Corrosion Flashcards
represents the greatest
destruction of metal on a tonnage
basis.
Uniform Corrosion
Metal deterioration that
happens in tight spaces where
a stagnant liquid gets trapped
Crevice Corrosion
Exists between two dissimilar
metals with potential difference
in a conductive solution.
Galvanic Corrosion
A highly localized form of attack that eats away at the metal,
creating small holes or cavities
Pitting Corrosion
Due to chemical
composition difference at
the grain boundaries from
the bulk of the grain.
Intergranular Corrosion
This type of corrosion
targets alloys, which are
mixtures of different metals.
Selective Leaching
The repeated impact of the particles can cause loss
of material that leads to pits, grooves, or cavities
Erosion Corrosion
Occurs when a metal is
exposed to a corrosive
environment under tensile
stress
Stress Cracking Corrosion
Can lead to various forms of
damage like embrittlement,
blistering, and cracking
Hydrogen Damage
Occurs in the presence of a
liquid containing ions
(electrolyte)
Wet Corrosion
Occurs at elevated
temperatures above 400°C
(750ºF) from gases, solid or
molten salts, or molten metals.
High- Temperature
Corrosion
The kinetics are influence by various
factors such as temperature, pH,
and presence of impurities.
Wet Corrosion
The kinetics are influenced by
factors such as diffusion rates and
electrolyte resistance.
High- Temperature
Corrosion
a generic term that
applies to high carbon-iron
alloys containing silicon.
Cast iron
Considered as the least
expensive of the engineering
metals.
Gray Cast Iron
have practically
all of the carbon in the form of
iron carbide
White Cast Iron
These are produced by hightemperature heat treatment of
white iron of proper
composition.
Malleable Cast Iron
The graphite is present as
nodules or spheroids as a
result of a special treatment of
the molten metal.
Ductile Cast Iron
The excellent corrosion resistance of
high silicon irons is due to the
formation of a passive _______
SiO2 surface
later
contains about 14.5% silicon
and 0.95% carbon.
Duriron
Composed of up to 2.14%
carbon
Steels
Contained at least 11%
chromium.
Stainless Steels
Can be hardened by heat
treatment similar to ordinary
steel.
Martensitic
Stainless Steels
Essentially nonmagnetic and
cannot be hardened by heat
treatment.
Austenitic
Stainless Steels
Can only be hardened by cold
working, just like Austenitic
stainless steel.
Ferritic
Stainless Steels
Hardened and strengthened by
solution-quenching, followed
by heating for substantial times
at temperature approximately in
the range of 800 to 1000 F.
Precipitation-hardened
Stainless Steels
is different from
most other metals in that it
combines corrosion
resistance with high
electrical and head
conductivity, formability,
machinability, and
strength when alloyed.
Copper
s have better
physical properties than copper
alone, and they are also more
resistant to impingement
attack; hence, brasses are
used in preference to copper for
condenser tubes.
Copper – Zinc Alloys
Lightweight metal having good
corrosion resistance to the
atmosphere and most aqueous
media
ALUMINUM
Has the lowest density of all
structural metals (1.7g/cm3
vs steel with 7.85g/cm3)
MAGNESIUM
Magnesium and magnesium alloys are resistant to:
Atmosphere
Distilled water
Alkalis
is ductile and
tough mainly because of its
face-centered cubic
structure.
Pure nickel
Consists of 10-30% copper
and 70-90% nickel
CUPRONICKELS
The mixture of formed
oxides (NiO and Cr2O3
)
combine to form nickel
chromite (NiCr2O4
) that
protects it from oxidation.
Nichrome
Impurities within a
metal can act as tiny
battery cells,
accelerating corrosion.
Conversely, purer
metals generally
exhibit better corrosion
resistance.
Metal Composition
The arrangement of
atoms in the metal’s
crystal lattice can
influence its
susceptibility to attack
by corrosive agents.
Crystal Structure
Highly acidic or
alkaline environments
(low or high pH,
respectively) can
significantly increase
corrosion rates for
most metals.
pH level
Oxygen often plays a
crucial role in many
corrosion processes,
acting as an oxidizing
agent.
Aeration
The presence of
___________ is essential
for most corrosion
processes to occur, as it
provides the necessary
conductive medium for
ionic movement.
Moisture
__________________ on
the metal can make it
more susceptible to
corrosion, especially
localized forms
Mechanical Stresses
In some environments,
microorganisms like
bacteria can accelerate
corrosion through
various mechanisms, a
phenomenon known as
_______________.
microbiologically
influenced corrosion
(MIC)
