Corrosion Glossary - N

Nanometer: abbreviated "nm", a unit of length equal to one thousandth of a micrometer.
Naphtha: a petroleum distillate used mostly by professionalsfor cleanup and to thin solvent-based coatings. A volatile organic compound (see VOC).
Natural aging: spontaneous aging of a supersaturated solid solution at room temperature. see also aging. compare with artificial aging.
Natural circulation: the circulation of water in a boiler caused by differences in density.
Natural gas: gaseous fuel occurring in nature.
Natural resins: resins from trees, plants, fish and insects.
Negative charge: the electrical charge on an electrode or ion in solution, due to the presence of an excess of electrons. (See electron, anion.)
Negative head: a condition of negative pressure or partial vacuum.
Negative pressure: a pressure below that of the surrounding atmospheric pressure at a specific point; a partial vacuum.
Nernst equation: an equation that expresses the exact electromotive force of a cell in terms of the activities of products and reactants of the cell.
Net positive suction head required (NPSHR): this is the minimum head required to stop the pump from cavitating when it is pumping cold water.
Neutral: in electrical systems, the term used to indicate neither an excess nor a lack of electrons; a condition of balance between positive and negative charges. In chemistry, the term used to indicate a balance between acids and bases; the neutral point on the pH scale is 7.0, indicating the presence of equal numbers of free hydrogen (acidic) and hydroxide (basic) ions.
Neutralization: the addition of either an acid or a base to a solution to control its pH. The use of alkaline or basic materials to neutralize the acidity of some waters is a common practice in water conditioning.
Neutralizer: A common designation for alkaline materials such as calcite (calcium carbonate) or magnesia (magnesium oxide) used in the neutralization of acid waters.
Neutron embrittlement: embrittlement resulting from bombardment with neutrons, usually encountered in metals that have been exposed to a neutron flux in the core of a reactor. In steels, neutron embrittlement is evidenced by a rise in the ductile-to-brittle transition temperature.
Nickel plating: the electrolytic deposition of nickel to form a corrosion barrier or to reclaim a worn part. Can also include hard ceramic particles to from a wear resistant composite coating.
Nitriding: introducing nitrogen into the surface layer of a solid ferrous alloy by holding at a suitable temperature in contact with a nitrogenous material, usually ammonia or molten cyanide of appropriate composition. Quenching is not required to produce a hard case.
Nitrocarburizing: any of several processes in which both nitrogen and carbon are absorbed into the surface layers of a ferrous material at temperatures below the lower critical temperature and, by diffusion, create a concentration gradient. Nitrocarburizing is performed primarily to provide an anti scuffling surface layer and to improve fatigue resistance.
Nitrogen: diatomic gas. Used as a primary and secondary gas in plasma spraying. Inert to most materials, with some exceptions like titanium.
Nitrogen dioxide: gas molecule consisting of one nitrogen atom and two oxygen atoms that is a combustion by-product of burning fossil fuels. The combustion temperature is high enough to oxidize atmospheric nitrogen.
Noble: the positive (increasingly oxidizing) direction of electrode potential.
Noble metal: a metal with a standard electrode potential that is more noble (positive) than that of hydrogen.
Noble potential: a potential more cathodic (positive) than the standard hydrogen potential.
Nodular powder: irregular particles having Knotted, rounded, or similar shapes.
Non carbonate hardness: water hardness due to the presence of compounds such as calcium and magnesium chlorides, sulfates or nitrates; the excess of total hardness over total alkalinity.
Nonrenewable: not able to be replaced. Fossil fuels are nonrenewable energy sources.
Nonvolatile: the portion of a coating left after the solvent evaporates; sometimes called the solids content.
Normal solution: an aqueous solution containing one gram equivalent of the active reagent in 1 liter of the solution.
Normal stress: the stress component perpendicular to a plane on which forces act.
Normalizing: heating a ferrous alloy to a suitable temperature above the transformation range and then cooling in air to a temperature substantially below the transformation range.
NOX: abbreviation for all of the family of oxides of nitrogen.
Nozzle: a short flanged or welded neck connection on a drum or shell for the outlet or inlet of fluids; also a projecting spout through which a fluid flows.
NPSHR: net positive suction head required.

Link to glossary of corrosion and materials maintenance terms