Ch 10 Flashcards
Define corrosion
Destructive attack of a metal by electro chemical interaction or chemical reaction with its environment
List the three conditions for corrosion
Oxidizing agent and Reducing agent
Must be thermodynamically favourable
Reaction occurs at surfaces of the material
What happens at the anode?
Oxidization
Loss of electrons
What happens at the cathode?
Reduction
Gain of electrons
What happens to oxidizing agents?
They’re reduced
What happens to reducing agents?
They’re oxidized
What is not typically involved in the cathode reaction for corrosion?
Metal ions
List the four components to an electrochemical cell, which all must be present for corrosion to occur
Anode
Cathode
Electrical connection
Electrolyte
What does the electrolyte do?
Conducts current via ions
Must be in contact with anode and cathode
How to stop corrosion
Remove one or more of the components from the electrochemical cell
Corrosion: what does passive mean?
Alloy forms, a protective layer
Corrosion: what does active mean?
When the alloy does not produce a protective layer
Why doesn’t stainless steel corrode
Because it corrodes very rapidly than forms, a protective layer, a very thin, inert metal oxide that prevents further reaction
For stainless steel the passive Cr2O3 layer forms
What does the galvanic series show
Inert and active
Define galvanic cell/composition cell
Galvanic corrosion occurs when dissimilar metals are connected and exposed to an electrolyte