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 solid surface.
Impingement corrosion: a form of erosion-corrosion generally associated with the local impingement of a high-velocity, flowing fluid against a solid surface.
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.
Industrial 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.
Ingot: 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.
Inhibitor: 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 inorganic vehicle.
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 symmetry.
Intercrystalline corrosion: See intergranular corrosion.
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 fracture.
Interlock: a device to prove the physical state of a required condition, and to furnish that proof to the primary safety control circuit.
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 the solid.
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.

Link to glossary of corrosion and materials maintenance terms