3- Metallic Corrosion Flashcards
2 factors that drive corrosion
thermodynamic (oxidation/reduction) and kinetic barriers
what properties does corrosion compromise in a material?
mechanical integrity
biocompatibility
aesthetics
what factors determine implant corrosion
– Thermodynamic forces that cause oxidation and reduction – Surface barrier such as surface oxide layer
what are some environmental factors that influence corrosion
ion concentration
fluid velocities
human body-conducive to corrosion
define ionization
formation of metallic cations under acidic or reducing conditions
M -> M++e-
define oxidation
reaction of a metal with oxygen
M + O2–> MO2
define hydroxylation
reaction of water under alkaline or oxidizing conditions
corroded state is what preferred energy state?
corroded state i preferred since lowest energy state
define galvanic series
Ranks the reactivity of metals/alloys in seawater
uniform attack
general corrosion that is evenly distributed over entire corrosion region… rusting iron, tarnishing of silverware….
most detectable/preventable
galvanic corrosion
two different metals/alloy that are in close proximity in an electrolytic enviornment..
bad… remember titanium femoral stems coupled with CoCr heads
crevice corrosion
found in crevices of deep, narrow flows at interface
can arise from localized oxygen depetion and metal ion concentration gradients
pitting corrosion
formation of pits; local thickness reduction, difficult to detect
intergranular corrosion
preferential attack along grain boundries
fretting
wear process due to relative motions in highly loaded devices exaggerated by corrosive environment
