Corrosion Glossary - L

Lacquer: a fast-drying usually clear coating that is highly flammable and dries by solvent evaporation only. Can be reconstituted after drying by adding solvent.
Lamellar corrosion: a form of corrosion in which the expanding corrosion products stack up as layers. Similar to exfoliation of high strength aluminum alloys.
Laminar flow: the flow of fluid in which the flow paths are in smooth, parallel lines, with essentially no mixing and no turbulence.
Langelier index: A calculated number used to predict the calcium carbonate (CaCO3) stability of a water; that is, whether a water will precipitate, dissolve, or be in equilibrium with calcium carbonate. It is sometimes erroneously assumed that any water that tends to dissolve calcium carbonate will always be corrosive.
Lanthanides: commonly referred to as 'Rare Earth' metals. Examples: Neodymium, Lanthanum and Yttrium.
Lap joint: a welded joint in which two overlapping metal parts are joined by means of a fillet, plug or slot weld.
Lapping: rubbing two surfaces together, with or without abrasives, for the purpose obtaining extreme dimensional accuracy or superior surface finish.
Laser alloying: the application of a powder to a surface followed by fusing and alloying into the surface via the heat from an impinging laser.
Laser glazing: the melting and quenching of a surface to form a fine grained structure or 'glaze'.
Laser hardening: the localized surface heating of a medium carbon steel by an incident laser so that the temperature is raised above 900oC. 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.
Latex-based paint: general term used for water-based emulsion paints made with synthetic binders such as 100% acrylic, vinyl acrylic, terpolymer or styrene acrylic. A stable emulsion of polymers and pigment in water.
Leaching: a process in which metal is extracted from mined ore by means of adding a soluble substance. Commonly used in gold mining.
Leakage: the uncontrolled quantity of fluid which enters or leaves through the enclosure of air or gas passages.
Life Cycle Costing: a process of estimating and assessing the total costs of ownership, operation and maintenance of an item of equipment during its projected equipment life. Typically used in comparing alternative equipment design or purchase options in order to select the most appropriate option.
Lime: the common name for calcium oxide (CAO). Hydrated lime is calcium hydroxide, Ca(OH)₂, the cement in concrete.
Lime scale: hard water scale containing a high percentage of calcium carbonate.
Limestone: a sedimentary rock, largely calcium carbonate, and usually also containing significant amounts of magnesium carbonate.
Linear alkyl sulfonate: a term applied to a family of straight chain chemical compounds, widely used as detergents; sometimes called "soft" detergents because they are more readily degraded to simpler substances by biological action than the previously used alkyl benzene sulfonate.
Lining: the material used on the furnace side of a furnace wall. it is usually of high grade refractory tile or brick or plastic refractory material.
Liquid impingement erosion: progressive loss of material from a solid surface due to continue exposure to impacts by liquid drops or jets.
Liquid metal embrittlement: catastrophic brittle failure of a normally ductile metal when in contact with a liquid metal and subsequently stressed in tension.
Liquid metal fast breeder reactor (LMFBR): nuclear reactor that uses a liquid metal, such as sodium, to transfer heat from the reactor to a steam generator. A breeder reactor makes more fuel than it uses by converting uranium-238 to plutonium-239.
Liquid penetrant examination (PT): a method of nondestructive examination. Typical discontinuities found with this method are cracks and laminations
Liter: the basic metric unit of volume; 3.785 liters equal 1 U.S. gallon; 1 liter of water weighs 1000 grams.
Lithopone: a white pigment of barium sulfate and zinc sulfide.
Load: the rate of output required; also the weight carried.
Load factor: the ratio of the average load in a given period to the maximum load carried during that period.
Local action corrosion: corrosion caused by local corrosion cells on a metal surface.
Local cell: a galvanic cell resulting from inhomogeneities between areas on a metal surface in an electrolyte. The inhomogeneities may be of physical or chemical nature in either the metal or its environment.
Local corrosion cell: an electrochemical cell created on a metal surface because of a difference in potential between adjacent areas on that surface.
Localized corrosion: corrosion at discrete sites, for example, pining, crevice corrosion, and stress corrosion cracking.
Logistic support analysis (LSA): A methodology for determining the type and quantity of logistic support required for a system over its entire lifecycle. Used to determine the cost effectiveness of asset based solutions.
Long-line current: electric current through the earth from an anodic to a cathodic area of a continuous metallic structure. (Usually used only where the areas are separated by considerable distance and where the current results from concentration-cell action.
Low water cutoff: safety device that shuts off the boiler/burner in the event of low water, preventing pressure vessel failure.
LPPS: see vacuum or low pressure plasma spraying.
Lubricant: any substance interposed between two surfaces for the purpose of reducing the friction or wear between them.
Lug: any projection, like an ear, used for supporting or grasping.
Luggin probe or Luggin-Haber capillary: a device used in measuring the potential of an electrode with a significant current density imposed on its surface. (The probe minimizes the IR drop that would otherwise be included in the measurement and without significantly disturbing the current distribution on the specimen.