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885oF (475oC) embrittlement. Embrittlement of stainless steels upon extended exposure to temperatures between 400 and 510oC (750 and 950oF). This type of embrittlement is caused by fine, chromium-rich precipitates that segregate at grain boundaries; time at temperature directly influences the amount of segregation. Grain-boundary segregation of the chromium-rich precipitates increases strength and hardness, decreases ductility and toughness. and changes corrosion resistance. This type of embrittlement can be reversed by heating above the precipitation range.
elastic deformation. A change in dimensions directly proportional to and in phase with an increase or decrease in applied force.
elasticity. The property of a material by virtue of which deformation caused by stress disappears upon removal of the stress. A perfectly elastic body completely recovers its original shape and dimensions after release of stress.
elastic limit. The maximum stress that a material is capable of sustaining without any permanent strain (deformation) remaining upon complete release of the stress. elastomer. A natural or synthetic polymer. which at room temperature can be stretched repeatedly to at least twice its original length, and which after removal of the tensile load will immediately and forcibly return to approximately its original length.
electrical conductivity. See conductivity.
electrical isolation. The condition of being electrically separated from other metallic structures or the environment.
electrical resistiviity. The electrical resistance offered by a material to the flow of current, times the cross-sectional area of current flow and per unit length of current path; the reciprocal of the conductivity. Also called resistivity or specific resistance.
electrochemical admittance. The inverse of electrochemical impedance.
electrochemical cell. An electrochemical system consisting of an anode and a cathode in metallic contact and immersed in an electrolyte. (The anode and cathode may be different metals or dissimilar areas on the same metal surface.)
electrochemical corrosion. Corrosion that is accompanied by a flow of electrons between cathodic and anodic areas on metallic surfaces.
electrochemical equivalent. The weight of an element or group of elements oxidized or reduced at 100% efficiency by the passage of a unit quantity of electricity. Usually expressed as grams per coulomb.
electrochemical impedance. The frequency-dependent complex-valued proportionality factor (dE/Ai) between the applied potential or current and the response signal. This factor is the total opposition (Ohms or Ohms.cm2) of an electrochemical system to the passage of charge. The value is related to the corrosion rate under certain circumstances.
electrochemical potential. The partial derivative of the total electrochemical free energy of a constituent with respect to the number of moles of this constituent where all factors are kept constant. It is analogous to the chemical potential of a constituent except that it includes the electric as well as chemical contributions to the free energy. The potential of an electrode in an electrolyte relative to a reference electrode measured under open circuit conditions.
electrochemical series. Same as electromotive force series. electrode. (1) An electronic conductor used to establish electrical contact with an electrolytic part of a circuit. (2) An electronic conductor in contact with an ionic conductor.
electrode polarization. Change of electrode potential with respect to a reference value. Often the free corrosion potential is used as the reference value. The change may be caused, for example by the application of an external electrical current or by the addition of an oxidant or reductant.
electrodeposition. The deposition of a substance on an electrode by passing electric current through an electrolyte.
electrode potential. The potential of an electrode in an electrolyte as measured against a reference electrode. The electrode potential does not include any resistance losses in potential in either the solution or external circuit. It represents the reversible work to move a unit charge from the electrode surface through the solution to the reference electrode.
electrode reaction. Interfacial reaction equivalent to a transfer of charge between electronic and ionic conductors. See also anodic reaction and cathodic reaction.
electrogalvanizing. The electroplating of zinc upon iron or steel.
electrokinetic potential. This potential, sometimes called zeta potential, is a potential difference in the solution caused by residual, unbalanced charge distribution in the adjoining solution, producing a double layer. The electrokinetic potential is different from the electrode potential in that it occurs exclusively in the solution phase; that is, it represents the reversible work necessary to bring a unit charge from infinity in the solution up to the interface in question but not through the interface.
electroless plating. A process in which metal ions in a dilute aqueous solution are plated out on a substrate by means of autocatalytic chemical reduction.
electrolysis. Production of chemical changes of the electrolyte by the passage of current through an electrochemical cell.
electrolyte. (1) A chemical substance or mixture usually liquid, containing ions that migrate in an electric field. (2) A chemical compound or mixture of compounds which when molten or in solution will conduct an electric current.
electrolytic cell. An assembly, consisting of a vessel, electrodes. and an electrolyte, in which electrolysis can be carried out.
electrolytic cleaning. A process of removing soil. scale. or corrosion products from a metal surface by subjecting it as an electrode to an electric current in an electrolytic bath.
electrolytic protection. See cathodic protection. electromotive force. Electrical potential; voltage. electromotive force series (emf series). A list of elements arranged according to their standard electrode potentials, with "noble" metals such as gold being positive and 'active" metals such as zinc being negative.
electron flow. A movement of electrons in an external circuit connecting an anode and cathode in a corrosion cell, the current flow is arbitrarily considered to be in an opposite direction to the electron flow. electroplating. Electrodepositing a metal or alloy in an adherent form on an object serving as a cathode.
electropolishing. A technique commonly used to prepare metallographic specimens, in which a high polish is produced by making the specimen the anode in an electrolytic cell, where preferential dissolution at high points smoothes the surface.
electrotinning. Electroplating tin on an object.
embrittlement. The severe loss of ductility or toughness or both, of a material, usually a metal or alloy. Many forms of embrittlement can lead to brittle fracture. Many forms can occur during thermal treatment or elevated temperature service (thermally induced embrittlement). Some of these forms of embrittlement, which affect steels, include blue brittleness, 885oF (475oC) embrittlement. quench-age embrittlement , sigma-phase embrittlement, strain-age embrittlement, temper embrittlement, tempered martensite embrittlement, and thermal embrittlement. In addition, steels and other metals and alloys can be embrittled by environmental conditions (environmentally assisted embrittlement). The forms of environmental embrittlement include acid embrittlement, caustic embrittlement, corrosion embrittlement, creep-rupture embrittlement, hydrogen embrittlement, liquid metal embrittlement, neutron embrittlement, solder embrittlement, solid metal embrittlement, and stress-corrosion cracking.
endurance limit. The maximum stress that a material can withstand for an infinitely large number of fatigue cycles. See also fatigue strength.
environment. The surroundings or conditions (physical, chemical, mechanical) in which a material exists.
environmental cracking. Brittle fracture of a normally ductile material in which the corrosive effect of the environment is a causative factor. Environmental cracking is a general term that includes corrosion fatigue, high-temperature hydrogen attack, hydrogen blistering, hydrogen embrittlement, liquid metal embrittlement, solid metal embrittlement, stress-corrosion cracking, and sulfide stress cracking. The following terms have been used in the past in connection with environmental cracking, but are becoming obsolete: caustic embrittlement, delayed fracture. season cracking, static fatigue, stepwise cracking, sulfide corrosion cracking, and sulfide stress-corrosion cracking. See also embrittlement.
environmentally assisted embrittlement. See embrittlement.
epoxy. Resin formed by the reaction of bisphenol and epichlorohydrin.
equilibrium (reversible) potential. The potential of an electrode in an electrolytic solution when the forward rate of a given reaction is exactly equal to the reverse rate. The equilibrium potential can only be defined with respect to a specific electrochemical reaction.
erosion. Destruction of metals or other materials by the abrasive action of moving fluids, usually accelerated by the presence of solid particles or matter in suspension. When corrosion occurs simultaneously, the term erosion-corrosion is often used.
erosion-corrosion. A conjoint action involving corrosion and erosion in the presence of a moving corrosive fluid, leading to the accelerated loss of material.
eutectic. (1) An isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling, the number of solids formed being the same as the number of components in the system. (2) An alloy having the composition indicated by the eutectic point on an equilibrium diagram. (3) An alloy structure of intermixed solid constituents formed by a eutectic reaction.
eutectoid. (1) An isothermal reversible reaction in which a solid solution is converted into two or more intimately mixed solids on cooling, the number of solids formed being the same as the number of components in the system. (2) An alloy having the composition indicated by the eutectoid point on an equilibrium diagram. (3) An alloy structure of intermixed solid constituents formed by a eutectoid reaction.
exchange current. When an electrode reaches dynamic equilibrium in a solution, the rate of anodic dissolution balances the rate of cathodic plating. The rate at which either positive or negative charges are entering or leaving the surface at this point is known as the exchange current.
exchange current density. The rate of charge transfer per unit area when an electrode reaches dynamic equilibrium (at its reversible potential) in a solution: that is. the rate of anodic charge transfer (oxidation) balances the rate of cathodic charge transfer (reduction).
exfoliation. Corrosion that proceeds laterally from the sites of initiation along planes parallel to the surface, generally at grain boundaries, forming corrosion products that force metal away from the body of the material, giving rise to a layered appearance.
external circuit. The wires, connectors, measuring devices, current sources, etc., that are used to bring about or measure the desired electrical conditions within the test cell. It is this portion of the cell through which electrons travel.
failure. A general term used to imply that a part in service (1) has become completely inoperable, (2) is still operable but is incapable of satisfactorily performing its intended function, or (3) has deteriorated seriously, to the point that it has become unreliable or unsafe for continued use.
Faraday's law. (1) The amount of any substance dissolved or deposited in electrolysis is proportional to the total electric charge passed. (2) The amounts of different substances dissolved or deposited by the passage of the same electric charge are proportional to their equivalent weights.
fatigue. The phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the tensile strength of the material. Fatigue fractures are progressive and grow under the action of the fluctuating stress.
fatigue crack growth rate, da/dN. The rate of crack extension caused by constant-amplitude fatigue loading, expressed in terms of crack extension per cycle of load application.
fatigue life. The number of cycles of stress that can be sustained prior to failure under a stated test condition.
fatigue limit. The maximum stress that presumably leads to fatigue fracture in a specified number of stress cycles. If the stress is not completely reversed, the value of the mean stress, the minimum stress, or the stress ratio should also be stated. Compare with endurance limit.
fatigue strength. The maximum stress that can be sustained for a specified number of cycles without failure, the stress being completely reversed within each cycle unless otherwise stated.
ferrite. (1) A solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated (for instance, as chromium ferrite), the solute is generally assumed to be carbon. On some equilibrium diagrams, there are two ferrite regions separated by an austenite area. The lower area is alpha ferrite; the upper, delta ferrite. If there is no designation, alpha ferrite is assumed. (21 In the field of magnetics, substances having the general formula: M2+O.M23+O3, the trivalent metal often being iron.
filiform corrosion. Corrosion that occurs under some coatings in the form of randomly distributed threadlike filaments.
film. A thin, not necessarily visible, layer of material.
fish eyes. Areas on a steel fracture surface having a characteristic white crystalline appearance.
flakes. Short, discontinuous internal fissures in wrought metals attributed to stresses produced by localized transformation and decreased solubility of hydrogen during cooling after hot working. In a fracture surface, flakes appear as bright silvery areas; on an etched surface, they appear as short. discontinuous cracks. Also called shatter cracks or snowflakes.
flame spraying. Thermal spraying in which a coating material is fed into an oxyfuel gas flame, where it is melted. Compressed gas may or may not be used to atomize the coating material and propel it onto the substrate.
foreign structure. Any metallic structure that is not intended as part of a cathodic protection system of interest.
fouling. An accumulation of deposits. This term includes accumulation and growth of marine organisms on a submerged metal surface and also includes the accumulation of deposits (usually inorganic) on heat exchanger tubing.
fouling organism. Any aquatic organism with a sessile adult stage that attaches to and fouls underwater structures of ships.
fractography. Descriptive treatment of fracture, especially in metals, with specific reference to photographs of the fracture surface. Macrofractography involves photographs at low magnification (<25x); microfractography, photographs at high magnification (>25x).
fracture mechanics. A quantitative analysis for evaluating structural behavior in terms of applied stress, crack length, and specimen or machine component geometry. See also linear elastic fracture mechanics.
fracture toughness. A generic term for measures of resistance to extension of a crack. The term is sometimes restricted to results of fracture mechanics tests, which are directly applicable in fracture control. However, the term commonly includes results from simple tests of notched or precracked specimens not based on fracture mechanics analysis. Results from test of the latter type are often useful for fracture control, based on either service experience or empirical correlations with fracture mechanics tests. See also stress intensity factor.
free carbon. The part of the total carbon in steel or cast iron that is present in elemental form as graphite or temper carbon. Contrast with combined carbon.
free corrosion potential. Corrosion potential in the absence of net electrical current flowing to or from the metal surface.
free ferrite. Ferrite that is formed directly from the decomposition of hypoeutectoid austenite during cooling, without the simultaneous formation of cementite. Also called proeutectoid ferrite.
free machining. Pertains to the machining characteristics of an alloy to which one or more ingredients have been introduced to give small broken chips, lower power consumption, better surface finish, and longer tool life; among such additions are sulfur or lead to steel, lead to brass, lead and bismuth to aluminum, and sulfur or selenium to stainless steel.
fretting. A type of wear that occurs between tight-fitting surfaces subjected to cyclic relative motion of extremely small amplitude. Usually, fretting is accompanied by corrosion, especially of the very fine wear debris.
fretting corrosion. The accelerated deterioration at the interface between contacting surfaces as the result of corrosion and slight oscillatory movement between the two surfaces.
furan. Resin formed from reactions involving furfuryl alcohol alone or in combination with other constituents.
galvanic anode. A metal which, because of its relative position in the galvanic series, provides sacrificial protection to metals that are more noble in the series, when coupled in an electrolyte.
galvanic cell. A cell in which chemical change is the source of electrical energy. It usually consists of two dissimilar conductors in contact with each other and with an electrolyte, or of two similar conductors in contact with each other and with dissimilar electrolytes
galvanic corrosion. Accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetallic conductor in a corrosive electrolyte.
galvanic couple. A pair of dissimilar conductors, commonly metals, in electrical contact. See also galvanic corrosion.
galvanic couple potential. See mixed potential.
galvanic current. The electric current that flows between metals or conductive nonmetals in a galvanic couple.
galvanic series. A list of metals and alloys arranged according to their relative corrosion potentials in a given environment. Compare with electromotive force series.
galvanize. To coat a metal surface with zinc using any of various processes.
galvanneal. To produce a zinc-iron alloy coating on iron or steel by keeping the coating molten after hot dip galvanizing until the zinc alloys completely with the base metal.
galvanometer. An instrument for indicating or measuring a small electric current by means of a mechanical motion derived from electromagnetic or electrodynamic forces produced by the current.
galvanostatic. An experimental technique whereby an electrode is maintained at a constant current in an electrolyte.
gaseous corrosion. Corrosion with gas as the only corrosive agent and without any aqueous phase on the surface of the metal. Also called dry corrosion.
gamma iron. The face-centered cubic form of pure iron, stable from 910 to 1400oC (1670 to 2550oF).
general corrosion. See uniform corrosion. Gibbs free energy. The thermodynamic function DeltaG = DeltaH - TDeltaS. where H is enthalpy, T is absolute temperature, and S is entropy. Also called free energy, free enthalpy, or Gibbs function.
glass electrode. A glass membrane electrode used to measure pH or hydrogen ion activity.
grain. An individual crystal in a polycrystalline metal or alloy: it may or may not contain twinned regions and subgrains.
grain boundary. A narrow zone in a metal corresponding to the transition from one crystallographic orientation to another, thus separating one grain from another; the atoms in each grain are arranged in an orderly pattern.
grain-boundary corrosion. Same as intergranular corrosion. See also interdendritic corrosion.
graphitic corrosion. Deterioration of gray cast iron in which the metallic constituents are selectively leached or converted to corrosion products leaving the graphite intact. The term graphitization is commonly used to identify this form of corrosion, but is not recommended because of its use in metallurgy for the decomposition of carbide to graphite. See also dealloying and selective leaching.
graphitization. A metallurgical term describing the formation of graphite in iron or steel. usually from decomposition of iron carbide at elevated temperatures. Not recommended as a term to describe graphitic corrosion.
green liquor. The liquor resulting from dissolving molten smelt from the kraft recovery furnace in water. See also kraft process and smelt.
groundbed. A buried item, sueh as junk steel or graphiterods, that serves as the anode for the cathodic protection of pipelines or other buried struetures. See also deep groundbed.
half cell. An electrode immersed in a suitable electrolyte, designed for measurements of electrode potential.
halogen. Any of the elements of the halogen family, consisting of fluorine. chlorine, bromine, iodine, and astatine.
hard chromium. Chromium plated for engineering rather than decorative applications.
hardenability. The relative ability of a ferrous alloy to form martensite when quenehed from a temperature above the upper critical temperature. Hardenability is commonly measured as the distance below a quenched surface at which the metal exhibits a specific hardness (50 HRC. for example) or a specific percentage of martensite in the microstructure.
hardfacing. Depositing filler metal on a surface by welding. spraying, or braze welding to increase resistance to abrasion, erosion, wear, galling. impact, or cavitation damage.
hard water. Water that contains certain salts, such as those of calcium or magnesium, which form insoluble deposits in boilers and form precipitates with soap.
heat-affected zone. That portion of the base metal that was not melted during brazing, cutting, or welding, but whose microstructure and mechanical properties were altered by the heat.
heat check. A pattern of parallel surface cracks that are formed by alternate rapid heating and cooling of the extreme surface metal. sometimes found on forging dies and piercing punches. There may be two sets of parallel cracks. One set perpendicular to the other.
hematite. (1) An iron mineral crystallizing in the rhombohedral system; the most important ore of iron. (2) An iron oxide, Fe2O3, corresponding to an iron content of approximately 70%.
high-temperature hydrogen attack. A loss of strength and ductility of steel by high-temperature reaction of absorbed hydrogen with carbides in the steel resulting in decarbnrization and internal fissuring.
holidays. Discontinuities in a coating (such as porosity, cracks, gaps, and similar flaws) that allow areas of base metal to be exposed to any corrosive environment that contacts the coated surface.
hot corrosion. An accelerated corrosion of metal surfaces that results from the combined effect of oxidation and reactions with sulfur compounds and other contaminants, such as chlorides, to form a molten salt on a metal surface that fluxes, destroys, or disrupts the normal protective oxide. See also gaseous corrosion.
hot cracking. Also called solidification cracking, hot cracking of weldments is caused by the segregation at grain boundaries of low-melting constituents in the weld metal. This can result in grain-boundary tearing under thermal contraction stresses. Hot cracking can be minimized by the use of low-impurity welding materials and proper joint design. See also cold cracking. Iamellar tearing and stress-relief cracking.
hot working. Deforming metal plastically at such a temperature and strain rate that recrystallization takes place simultaneously with the deformation, thus avoiding any strain hardening. Contrast with cold working.
hot dip coating. A metallic coating obtained by dipping the base metal into a molten metal.
hot shortness. A tendency for some alloys to separate along grain boundaries when stressed or deformed at temperatures near the melting point. Hot shortness is caused by a low-melting constituent, often present only in minute amounts, that is segregated at grain boundaries.
humidity test. A corrosion test involving exposure of specimens at controlled levels of humidity and temperature. Contrast with salt-fog test.
hydrogen-assisted cracking (HAC). See hydrogen embrittlement.
hydrogen-assisted stress-corrosion cracking (HSCC). See hydrogen embrittlement.
hydrogen blistering. The formation of blisters on or below a metal surface from excessive internal hydrogen pressure. Hydrogen may be formed during cleaning, plating, corrosion, and so forth.
hydrogen damage. A general term for the embrittlement, cracking, blistering. and hydride formation that can occur when hydrogen is present in some metals.
hydrogen embrittlement. A process resulting in a decrease of the toughness or ductility of a metal due to the presence of atomic hydrogen. Hydrogen embrittlement has been recognized classically as being of two types. The first, known as internal hydrogen embrittlement, occurs when the hydrogen enters molten metal which becomes supersaturated with hydrogen immediately after solidification. The second type. environmental hydrogen embrittlement, results from hydrogen being absorbed by solid metals. This can occur during elevated-temperature thermal treatments and in service during electroplating, contact with maintenance chemicals, corrosion reactions, cathodic protection, and operating in high-pressure hydrogen. In the absence of residual stress or external loading. environmental hydrogen embrittlement is manifested in various forms, such as blistering, internal cracking, hydride formation, and reduced ductility. With a tensile stress or stress-intensity factor exceeding a specific threshold, the atomic hydrogen interacts with the metal to induce subcritical crack growth leading to fracture. In the absence of a corrosion reaction (polarized cathodically), the usual term used is hydrogen-assisted cracking (HAC) or hydrogen stress cracking (HSC). In the presence of active corrosion, usually as pits or crevices (polarized anodically), the cracking is generally called stress-corrosion cracking (SCC). but should more properly be called hydrogen-assisted stress-corrosion cracking (HSCC). Thus, HSC and electrochemically anodic SCC can operate separately or in combination (HSCC). In some metals, such as highs-strength steels, the mechanism is believed to be all, or nearly all, HSC. The participating mechanism of HSC is not always recognized and may be evaluated under the generic heading of SCC.
hydrogen-induced cracking (HIC). Same as hydrogen embrittlement.
hydrogen overvoltage. Overvoltage associated with the liberation of hydrogen gas.
hydrogen stress cracking (HSC). See hydrogen embrittlement.
hydrolysis. (1) Decomposition or alteration of a chemical substance by water. (2) In aqueous solutions of electrolytes, the reactions of cations with water to produce a weak base or of anions to produce a weak acid.
hydrophilic. Having an affinity for water. Contrast with hydrophobic.
hydrophobic. Lacking an affinity for, repelling, or failing to absorb or adsorb water. Contrast with hydrophilic. hygroscopic. (1) Possessing a marked ability to accelerate the condensation of water vapor; applied to condensation nuclei composed of salts that yield aqueous solutions of a very low equilibrium vapor pressure compared with that of pure water at the same temperature. (2) Pertaining to a substance whose physical characteristics are appreciably altered by effects of water vapor. (3) Pertainirig to water absorbed by dry soil minerals from theatmosphere; the amounts depend on the physicochemical character of the surfaces, and increase with rising relative humidity.
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 corrosion. A form of erosion-corrosion generally associated with the local impingement of a high-velocity, flowing fluid against a solid surface.
impressed current. Direct current supplied by a device employing a power source external to the electrode system of a cathodic protection installation.
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 corrodent.
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.
inhibitor. A chemical substance or combination of substances that, when present in the environment, prevents or reduces corrosion without significant reaction with the components of the environment.
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 zinc-rich paint. Coating containing a zinc powder pigment in an inorganic vehicle.
intensiostatic. See galvanostatic.
intercrystalline corrosion. See intergranular corrosion.
intercrystalline cracking. See intergranular cracking.
interdendritic corrosion. Corrosive attack that progresses preferentially along interdendritic paths. This type of attack results from local differences in composition, such as coring commonly encountered in alloy castings.
intergranular. Between crystals or grains. Also called intercrystalline. Contrast with transgranular.
intergranular corrosion. Corrosion occurring preferentially at grain boundaries, usually with slight or negligible attack on the adjacent grains. Also called intercrystalline corrosion.
intergranular cracking. Cracking or fracturing that occurs between the grains or crystals in a polycrystalline aggregate. Also called intercrystailine cracking. Contrast with transgranular 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 .
intergranular stress corrosion cracking (ICSCC). Stress-corrosion cracking in which the cracking occurs along grain boundaries.
intermediate electrode. Same as bipolar electrode.
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, and so forth.
intumescence. The swelling or bubbling of a coating usually because of heating (term currently used in space and fire protection applications).
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.
iron rot. Deterioration of wood in contact with iron-based alloys.
isocorrosion diagram. A graph or chart that shows constant corrosion behaviour with changing solution (environment) composition and temperature.
