Corrosion Flashcards
What is corrosion?
Includes all the interactions between the environment and the metallic surface
The major factors are the micro environemtn like composition of the metals, temperature, pH, oxygen dissolved
What is electrochemical corrosion?
Occurs when a metal reacts with an electrolyt, such as water.
The metal is an anode, the electrolyte is the cathod (the cathod can also be another metal)
The anode gives electrone to the cathod
Oxidation happens at the anode
Describe the corrosion process for Zinc
Zinc react with oxygen and water to form Zn²⁺ and OH-.
At the anode the oxidation happens when the Zn looses electrones.
At the cathode is where the oxygen reduction happens where the oxygen and water picks up the electrons and becomes hydroxide OH-
What is wet corrosion?
Wet corrosion is electrochemical corrosion
What is dry corrosion?
No liquid electrolyte, exists in dry environments, due to gases instead.
What is corrosion rate?
Refers to the speed at which the corrosion happens in
The corrosion can have an active behavior or an actie-passive behavior (forms a barrier)
What are som rules of thumb for corrosion?
Moist air is more corrosive than dry air
Hot air is more corrosive than cold air
Hot water is more corrosive than cold water
Polluted air is more corrosive than clean air, like industrial environments
Acids are more corrosive than bases (alkalies) to steels
Salt water is more corrosive than freshwater
Stainless steel will outlast ordinary steel
No corrosion will occur in a vacuum, even at very high temperatures
Which are the different types of corrosion?
Uniform corrosion
Galvanic corrosion
Differential aeration corrosion
Pitting corrosion
Crevice corrosion
Intergranular corrosion
Stress corrosion
