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Corrosion Glossary - I
- Ignition: the initiation of combustion.
- Immersion plating: depositing a metallic
coating on a metal immersed in a liquid solution, without the aid of an external
electric current. Also called dip plating.
- Immunity: a state of resistance to corrosion
or anodic dissolution of a metal caused by
thermodynamic stability of the metal.
- Impingement: a process resulting in
a continuing succession of impacts between (liquid or solid) particles and a
- Impingement corrosion: a form of
erosion-corrosion generally associated
with the local impingement of a high-velocity, flowing fluid against a solid
- Impregnation: a process of filling the
pores of a coating with resin,
wax or oil.
- Impressed current:
an electric current supplied by a device employing a power source that is external
to the electrode system. (An example is d~ current for cathodic protection).
- Inclusions: particles of foreign material
in a metallic matrix. the particles are usually compounds (such as oxides, sulfides,
or silicates), but may be of any substance that is foreign to (and essentially
insoluble in) the matrix.
- Incubation period: a period prior to
the detection of corrosion while the metal is in contact with a corrosive agent.
- Indicator: a material which can be used
to show the endpoint of a chemical reaction, usually by a color change, or a
chemical concentration by a depth or shade of color.
- Induction heating: the heating of a
electrically conductive material by an induction coil producing alternating
magnetic fields which induce alternating electric currents to flow in the material
and cause heating by resistance. Used in many heating process (induction fusing,
induction plasma, induction hardening etc..).
- Induction hardening: the localized surface
heating of a medium carbon steel by an induction coil so that the temperature
is raised above 900°C. The part is quenched (or self-quenches by virtue of the
remaining cool bulk of the component) and tempered to produce a hard martensitic
structure at the surface.
atmosphere: an atmosphere in an area of heavy industry with soot,
fly ash, and sulfur compounds as the principal constituents.
- Inert anode:
an anode that is insoluble in the electrolyte under the conditions prevailing
in the electrolysis.
- Infant Mortality: The relatively high
conditional probability of failure during the period immediately after an item
returns to service.
- Influent: the stream entering a unit,
stream or process, such as the hard water entering an ion exchange water softener.
steel cast in a
metal mold ready for rolling or forging.
It is distinct from a casting, which is not rolled or forged. Ingots are usually
rectangular, called slabs; square, called blooms, polygonal, eight- or 12-sided
for forging. Squares and polygonal ingots can be fluted or corrugated to increase
the surface area and reduce the tendency to crack while cooling.
a chemical substance or combination of sub-stances that, when present in the
proper concentration and forms in the environment, prevents or reduces corrosion.
- Injector: a device utilizing a steam
jet to entrain and deliver feed water into a boiler.
- Inorganic: being or composed of matter
other than hydrocarbons and their derivatives, or matter that is not of plant
or animal origin. contrast with organic.
- Inorganic matter: matter which is not
derived from living organisms and contains no organically produced carbon; includes
rocks, minerals and metals.
- Inorganic zinc-rich paint:
coating containing a
zinc powder pigment in an
- Insulation: a material of low thermal
conductivity used to reduce heat losses.
- Intensiostatic: See galvanostatic.
- Interconnected porosity: a network of
pores in and extending to the surface of a coating.
- Ion-Implantation: a process in which
a beam of positive ions is projected towards and into the surface. It is carried
out in partial vacuum and the ions diffuse into the surface layer of the substrate.
Typically this is carried out with nitrogen giving a nitrided effect.
- Ion nitriding: also called plasma nitriding.
A vacuum glow discharge technique of nitriding. See Nitriding.
- Ion plating: a process in which positive
ions produced in a glow discharge are attracted to the substrate which is connected
as the cathode. The ions are typically made by evaporation.
- Irregular powder: particles lacking
- Intercrystalline corrosion: See intergranular
- Intergranular: between crystals or grains.
- Intergranular corrosion: preferential
corrosion at or adjacent to the grain boundaries of a metal or alloy.
- Intergranular cracking:
cracking or fracturing that occurs between the grains or crystals in a polycrystalline
aggregate. Also called intercrystalline cracking.
- Intergranular fracture: brittle fracture
of a metal in which the fracture is between the grains, or crystals, that form
the metal. also called intercrystalline fracture. contrast with transgranular
- Interlock: a device to prove the physical
state of a required condition, and to furnish that proof to the primary safety
- Intermittent blowdown: the blowing down
of boiler water at intervals.
- Internal oxidation: the formation of
isolated particles of corrosion products beneath the metal surface. (This occurs
as the result of preferential oxidation of certain alloy constituents by inward
diffusion of oxygen, nitrogen, sulfur, etc.).
- Internal treatment: the treatment of
boiler water by introducing chemicals directly into the boiler.
- Intumescence: a mechanism whereby fire-retardant
paints protect the substrates to which they are applied. An intumescent paint
puffs up when exposed to high temperatures, forming an insulating, protective
layer over the substrate.
- Ion: an atom, or group of atoms, that
has gained or lost one or more outer electrons and thus carries an electric
charge. Positive ions, or cations, are deficient in outer electrons. Negative
ions, or anions, have an excess of outer electrons.
- Ion exchange: the reversible interchange
of ions between a liquid and solid, with no substantial structural changes in
- Ion exchange: a reversible process in
which ions are released from an insoluble permanent material in exchange for
other ions in a surrounding solution; the direction of the exchange depends
upon the affinities of the ion exchanger for the ions present, and the concentrations
of the ions in the solution.
- Ion exchanger: a permanent, insoluble
material which contains ions that will exchange reversibly with other ions in
a surrounding solution. Both cation and anion exchangers are used in water conditioning.
- Ionization: the process in which atoms
gain or lose electrons; sometimes used as synonymous with dissociation, the
separation of molecules into charged ions in solution.
- Ionization constant: a constant specific
for each partially ionizable chemical compound to express the ratio of the concentration
of ions from the compound to the concentration of undissociated compound.
- Iron bacteria: microorganisms which
are capable of utilizing ferrous iron, either from the water or from steel pipe,
in their metabolism, and precipating ferric hydroxide in the sheaths and gelatinous
deposits. These organisms tend to collect in pipe lines and tanks during periods
of low flow, and to break loose in slugs of turbid water to create staining,
taste and odor problems.
- Isocorrosion diagram: a graph or chart
that shows constant corrosion behavior with changing solution (environment)
composition and temperature.