Corrosion 3 Flashcards
typically refers to the
degradation of metals due to chemical
reactions with their environment,
leading to deterioration and loss of
material.
Corrosion
occur when polymers are
exposed to heat above a
specified temperature limit
Chain Scission from Heat
is highly
dependent on the molecule structure
whether amorphous or crystalline.
Crystalline are more resistant to
organic substances and solvents
than amorphous polymers
Chemical resistance
Physical effects on polymers may lead to
swelling, dissolving or leakage of additives
small molecules infiltrate the structure
swelling
According to IUPAC, polymers are
substances composed of
macromolecules
The most common form of degradation
decrease in polymer chain length
the penetration of the
plastic by a corrodent, which causes
softening, swelling, and ultimate failure
Solvation
is caused by photons or light-breaking chemical bonds. Light of
any wavelength shorter than the threshold will break a bond, while longer wavelengths cannot
fracture it.
Photochemical degradation
is a molecular migration
through microvoids either in the
polymer or between polymer
molecules. This action is strictly a
physicalphenomenon
Permeation
can cause softening of the polymer,
introduce high stresses, and cause failure of
the bond on lined component
Swelling
is a material that is neither
metallic nor organic. It may be
crystalline, glassy or both crystalline
and glassy
ceramic
When compared to steel and plastic polymers,
technical ceramics offer
superior corrosion
resistance
they are exceedingly immune
to corrosion by almost all
environments, especially at room
temperature.
Ceramic materials
The solid material dissolves directly into the liquid through
dissociation or reaction with the solvent
Direct Dissolution
The corrosion process of a solid material by a liquid can
involve the formation of an interface or reaction product
between the solid and the solvent. This reaction product
mayor may not create an attached surface layer.
Indirect Dissolution
tend to be soluble in polar solvents (e.g.,
salt in water) and covalent materials tend to be soluble in
nonpolar solvents (e.g., SiC in hexane).
Ionic materials
is typically manufactured to
harness the optimal properties of two or more
materials, aiming to enhance overall
performance or capture specific attributes of
each component
composite
is highly stable in oxidizing atmospheres up to
1090°C, while boron nitride is stable only up to 850°C
Boron carbide
are commonly used in composites for low temperature applications, particularly in polymer matrices for
marine or moist environments.
Glass fibers
is defined as a process in which the
object due to applied force changes its size or shape in a
way that is not reversible
Plastic deformation
involves the sliding of blocks of crystal
over one another along different crystallographic
planes known as slip planes
slip
the portion of
crystals takes up an orientation related to the
orientation of the rest of the untwined lattice in a
symmetrical and definite way
twinning
is the development of a network
of fine random cracks or fissures on the
surface of concrete or mortar caused by
shrinkage of the surface layer
Crazing
is a failure mechanism that
involves the cracking of materials and
structural components due to cyclic (or
fluctuating) stress
Fatigue
is the stress produced by
any change in the temperature of the
material.
Thermal stress
is the deterioration of a
material from its initial state due to time
Physical aging
is a hygroscopic material, meaning that it will
continually trying to achieve an equilibrium conditionwith
its environment
Wood
or cracking, is one symptom of non-uniform
drying, and it is common and typically not structurally
significant
Checking
is the process by which
a substance is altered via photons,
especially those found in the wavelengths
of the sun’s rays.
Photodegradation
can undergo chemical
deterioration due to exposure to acids, alkalis, salts, or
other corrosive substances, which can result in changes
to their composition or structure.
Non-metallic materials
melt when heated up and
solidify when cooled down.
Thermoplastics
Usually causes a pronounced decrease in corrosion rate.
Lowering temperature
Often used as a practical method of corrosion
control.
Decreasing velocity
In modern practice, this is accomplished by vacuum
treatment, inert gas sparging, or through the use of oxygen
scavengers
Removing oxygen or oxidizers
Decreasing corrosive concentration is usually elective
Changing concentration
have the ability to be
reheated, remolten, and resolified.
thermoplastic coating
