My Account
View Quote (0)
Submit Quote|
Corrosion Monitoring Products
Markets and Applications
Field Services and Training
CONTACT US
|
Home » Corrosion Glossary
Corrosion GlossaryA | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U |V | W | X |Y |Z  Corroded Fittings Active - A state in which a metal tends to corrode (opposite of passive). Anion - an ion or radical which is attracted to the anode because of the negative charge on the con or radical (as Cl-, OH-). Anode - (Opposite of cathode) the electrode at which oxidation or corrosion occurs. Anodic Inhibitor - An inhibitor of metal corrosion that reduces the rate of the anodic or corrosion reaction. Auxiliary Electrode - The electrode of an electrochemical cell that is used to transfer current to or from a test electrode. Bandwidth - (Ultrasonics) Range of frequencies around a mean value that constitutes the nominal frequency. Cathode - (Opposite of anode) the electrode where reduction (and practically no corrosion) occurs. Cathodic Protection - Reduction or elimination of corrosion by making the metal a cathode by means of an impressed DC current or attachment to a sacrificial anode (usually Mg, Al, or Zn). Cation - A positively charged ion (as H+, Zn++) or radical (as NH4+) which migrates toward the cathode. Cell - A circuit consisting of an anode and a cathode in electrical contact with a solid or liquid electrolyte. Concentration Cell - An electrolytic cell, the EMF of which is caused by a difference in concentration of some component in the electrolyte. (This difference leads to the formation of discrete cathode and anode regions). Corrosion - The chemical deterioration of a material, usually a metal, because of a reaction with its environment. Corrosion Inhibitor - A substance which sharply reduces corrosion when added in small amounts to water, acid or other liquid. Corrosion Potential - The potential of a corroding surface in an electrolyte relative to a reference electrode measured under open-circuit conditions. Corrosion Rate - The amount of corrosion occurring in unit time. (For example, mass change per unit area per unit time; penetration per unit time). Coupons - Specimens of materials exposed to tests or real environments to assess the effect of degradation on the material. Crevice Corrosion - Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from full exposure to the environment because of close proximity between the metal and the surface of another material. chemical deterioration of a material, usually a metal, because of a reaction with its environment. Current Density - The electrical current flowing to or from a unit area of an electrode surface. Depolarization - The elimination or reduction of polarization by physical or chemical means; depolarization results in increased corrosion. Electrochemical Impedance Spectroscopy (AC Impedance) - A method to study the impedance of a metal/fluid interface by electrochemical properties by applying a sinusoidal polarization potential to the interface through a range of frequencies. Electrolyte - An ionic conductor (usually in aqueous solution). Electromotive Force Series (EMF Series) - 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-Corrosion - Corrosion which is increased because of the abrasive action of a moving stream; the presence of suspended particles greatly accelerates abrasive action. Exfoliation - A thick, layer-like growth of loose corrosion products (observed in some cases on steel and aluminum alloys). Fretting Corrosion - Fretting refers to metal deterioration caused by repetitive slip at the interface between two surfaces. When metal loss is increased by corrosion, the term "fretting corrosion" should be used. 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 Series - A list of metals arranged according to their relative corrosion potentials in some specific environment; sea water is often used. General Corrosion - Corrosion in a uniform manner. Half Cell - A pure metal in contact with a solution of known concentration of its own ion, at a specific temperature, develops a potential which is characteristic and reproducible; when coupled with another half cell, an overall potential develops which is the sum of both half cells. Heat Affected Zone (HAZ) - Refers to area adjacent to a weld where the thermal cycle has caused microstructural changes which generally affect corrosion behavior. Hydrogen Embrittlement - Hydrogen-induced cracking (HIC) or severe loss of ductility caused by the presence of hydrogen in the metal. (Often generated from atomic hydrogen produced from cathodic reactions). Hydrogen Probes - Probes designed to measure the permeation rate of atomic hydrogen H+ (measured as hydrogen gas H2) associated with hydrogen-induced cracking. Impressed Current - An electric current supplied by a power source that is external to the electrode system. (An example is DC current for cathodic protection). Inhibitor - A chemical substance or combination of substances that, when present in the proper concentration and forms in the environment, prevents or reduces corrosion. Intergranular Corrosion - Corrosion which occurs preferentially at grain boundaries. Linear Polarization Resistance (LPR) - (see Polarization Resistance). At small applied polarization potentials, the Relationship between applied potential approximates the polarization resistance. Microbiologically-Influenced Corrosion (MIC) - Corrosion which is substantially increased as the result of the presence of bacteria (such as sulfate reducing bacteria, S.R.B.; or acid-producing bacteria, A.P.B. Noble Metal - A metal which is not very reactive (assilver, gold, or copper) and may be found naturally in metallic form on earth. Oxygen Concentration Cell - A galvanic cell caused by a difference in oxygen concentration at two points on a metal surface. Passive - The state of a metal when it is much more resistant to corrosion than its position in the EMF series would predict. Passivation is a surface phenomenon. Pitting - Highly localized corrosion resulting in deep penetration at only a few spots. Polarization - The shift in electrode potential resulting from the effects of current. Polarization Resistance - The slope (dE/di) at the corrosion potential of a potential (E) versus current density (i) curve. (It is inversely proportional to the corrosion current density when the polarization resistance technique is applicable). Potential Surveys - Measurement of potential of a structure or pipeline relative to a reference electrode potential pitting Pulse Width - (Ultrasonics) Duration time of a single transmitted pulse. Radiography (X-ray) - Use of X-rays to measure thickness or imperfection within solid materials. Redox Potential - The potential of a reversible oxidation-reduction electrode measured with respect to a reference electrode, corrected to the hydrogen electrode, in a given electrolyte. Resolution - (Ultrasonics) The ability of a system to give simultaneous separate indications from discontinuities that are close together both in depth and lateral position Sacrificial Anode - The use of an alloy electrode less noble than the structure to which it is connected, to induce galvanic corrosion on the electrode (anode) in preference to that of the structure. Selective Corrosion - The selective corrosion of certain alloying constituents from an alloy (as dezincification), or in an alloy (as internal oxidation). Soil Resistivity - The electrical resistivity of the soil. This is important in cathodic protection systems as it affects current distribution through the soil and potentials on the protected structure. Stress Corrosion or Stress-Accelerated Corrosion - Corrosion which is accelerated by stress. Stress Corrosion Cracking - Cracking which results from stress corrosion. Tafel Slope - The slope of the linear portion of a plot of potential versus the log of the current density for a particular electrode in a corroding system. Ultrasonic Measurement - The timing of the transmission of ultrasonic sound waves through a material to determine the material's thickness. Uniform Corrosion - (see General Corrosion). |