Download Corrosion Glossary - N Nanometer: abbreviated "nm", a unit of

Corrosion Glossary - N
Nanometer: abbreviated "nm", a unit of length equal to one thousandth
of a micrometer.
Naphtha: a petroleum distillate used mostly by professionals for 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.