Exam 1 (Ch. 5-6) Flashcards
(metals/ceramics) are more susceptible to degradation in vivo?
metals
___________ is characterized by the leaching of ions from a metallic surface into the surrounding environment
corrosion
corrosion occurs through the coupling of ___________ and _____________ reactions
oxidation (generates electrons) and reduction (consumes electrons)
oxidation occurs at the (anode/cathode)
anode (vowels)
in a galvanic cell (or battery), electrons flow from….
the anode (more negative standard reduction potential) to the cathode (alphabetical)
in galvanic corrosion, what acts as the salt bridge? which metal dissolves faster?
physiological fluid, and the more active metal (anodic) dissolves faster
what does a Pourbaix diagram show?
for a given metal, a Pourbaix diagram shows regions of corrosion and non-corrosion as a function of cell potential and pH. diagonal dashed lines represent the stability of water - aqueous corrosion occurs between them
what are the three main regions on the Pourbaix diagram? order them top to bottom
passivation, corrosion, immunity
in the immune region of a Pourbaix diagram, it is not energetically favorable for corrosion to occur. what is this also called?
cathodic protection (the metal cannot act as an anode)
define passivation
oxidation on the surface leads to the formation of a stable solid film that coats the metal and prevents electrons from flowing in or out
_______ corrosion occurs when oxygen is depleted within a narrow, deep crack, creating an anode and decreasing local pH
crevice
________ corrosion occurs when the passivation film on the surface is disrupted (think a car’s paint job)
pitting
__________ corrosion occurs at the grain boundaries, which tend to be anodic because they are higher energy
intergranular
stress corrosion cracking leads to ___________ in metals
brittle fracture
_________ corrosion occurs due to continued bending, loading, or motion
fatigue
________ corrosion is unique in that it is not related to loading, and involves removal of the passivating layer by mechanical means
fretting
______ _________ involves breaking primary bonds and can occur via hydrolysis or oxidation reactions
chain scission
how can the presence of metals near polymeric components increase their degradation?
metal-catalyzed oxidation occurs, which forms strong oxidizing agents that attack the polymer coating, leading to brittle fracture
what are other ways polymers can degrade?
enzyme-catalyzed degradation, environmental stress cracking
degradation is ________, while erosion is ________
the breaking of chemical bonds within a material, any change in the size or shape of a material (broader)
ceramic bioerosion occurs mainly due to…
interactions with water
(hydrated/nonhydrated) ceramics degrade faster
hydrated
polycrystalline materials are _________ but ____________ than single-crystal
stronger but degrade faster
synthetic polymers can degrade via _________ or __________, while natural polymers can only degrade via _________
hydrolysis or enzyme interaction, enzyme interaction
