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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
- Natural resins:
resins from trees, plants, fish
- 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
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
- 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
- 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
- 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
- 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
- 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.