Chapter 2 Corrosion Flashcards
Define corrosion
The deterioration of a material, usually a metal, that results from a reaction with its environment
What is passivation?
A layer of oxides formed on the surface of a metal that provides corrosion protection. Stainless steel for example.
What are the elements of a corrosion cell?
Anode, Cathode, Metallic Pathway, Electrolyte
Describe what happens at the anode
The metal dissolves into the electrolyte
What is the electrolyte?
A Conductive medium in which ions are carried from the anode to the cathode.
What is the function of the metallic pathway?
Allows the passage of electrons between the anode and cathode
What is the galvanic series?
A listing of metals in order of reactivity (more or less noble) in seawater at 25*C
The general rules of galvanic corrosion are:
The less noble ( or more reacitive ) metal when connected to a more noble ( or less reactive metal ) will corrode preferentially
Name at least five factors that affect the rate of corrosion.
Oxygen, Temperature, Chemical Salts, Humidity (wetness), Pollutants & Acid Gases
General corrosion is:
Results in a relatively uniform loss of material over the entire surface.
Results in a general thinning of the affected surface.
Relatively east to inspect.
Does no cause catastrophic failures.
Localized corrosion is:
Typically Pitting and Crevice Corrosion. It is typically of the most concern as damage is concentrated and loss of integrity or structural failure can result.
List some of the common tools/methods used for corrosion control
Design, Inhibitors, Material selection, Cathodic protection, Protective coatings, Alteration of the environment
