CHMA11H3 Lecture Notes - Lecture 34: Electrowinning, Electrosynthesis, Electroplating

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CHMA11 Lecture 31: Applications of Electrochemistry
- Industrial Applications of electrolysis
o Electroplating: platting a less expensive metal with a drastically more expensive,
pure type
Done to prolong the life of metals
o Electrorefining: extracting the refined from of a metal from the raw ore form
o Electrosynthesis: process of using electrolysis to synthesize various compounds
- Rust formation
o Corrosion: unwanted voltaic cell activity that results in unwanted oxidation
yielding rust
These reactions tend to be spontaneous
Corrosion is enhanced in acidic solutions
Strained regions of metals like the tip or bend sections are more anodic
and acidic
Results in preferential rusting in these regions
o Regions become oxidized more
Also more active metals tend to have a greater oxidation ability
o Makes them get oxidized and thus more corrosion prone
than less active metals
o Sacrificial Anodes: using a metal more acidic than the target metal you want to
protect in order to surround and protect the target metal
The more acidic surrounding metal will be more active
Has to be in electrical contact with the metal you want to protect
The more active metal will thus get oxidized and rust
o Keeps the target metal underneath from rusting
o Process of rust formation
Most common site of corrosion is the interface between the anodic
region of the metal and a given water droplet
This is the section of the metal at which it loses an electron and
forms an ion
The cathodic region is represented by the very edge and surface of the
water droplet
It will pick up an electron from the anodic region of the metal
This electron interacts with the water and causes it to lose a
o Yields a hydroxide ion
Therefore the transferred electron, metal ion and hydroxide are all of the
reactants needed to initiate rust formation
These substances initiate a cascade of other reactions
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