Fundamental of corrosion

The deterioration of materials due to reactions with their environments
is the currently accepted broad definition of corrosion. From a
practical standpoint, the term materials refers to those substances used
in the construction of machines, process equipment, and other manufactured
products. These materials include metals, polymers, and ceramics.
The environments are liquids or gases, although under special circumstances
certain solid-solid reactions might be included as
corrosion. The breadth of this definition can best be appreciated by considering
examples, starting with cases that are usually recognized as
corrosion and proceeding to those that are less obvious or are not generally
recognized as corrosion:
• Rusting of steel and cast iron in water, including humid air, as occurs
with domestic and industrial water tanks and supply piping, automobiles,
and exposed steel structures
• Corrosion of copper, aluminum, and cast iron in automotive cooling
systems
• Corrosion of iron-base, copper-base, nickel-base, etc. alloys in the
chemical process industry
• Corrosion of automobile exhaust systems by direct reaction of the
metal with high-temperature gases and by condensation of water
and absorption of the oxides of sulfur and nitrogen to produce aqueous
acid environments
• Corrosion of turbine blades in gas turbines by hot combustion gases
• Corrosion of metallic surgical implant materials used in orthopedic,
cardiovascular, and dental devices resulting in the release of metal
ions to tissues, and degradation of the physical properties of polymeric
implant materials due to interactions with tissue fluids and/or
blood
• Corrosion of iron-base and nickel-base alloys by liquid metals used
as heat transfer agents (e.g., liquid sodium, potassium, and lithium)
• Enhanced deterioration of structural concrete and stone by interaction
with condensed moisture and acidic contaminants in the air,
such as the oxides of sulfur and nitrogen
• Stress-corrosion cracking (SCC) of gold and brass by mercury
• SCC and pitting of stainless steel in sea water