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Corrosion Glossary - M
- Macrohardness: the hardness of a
coating as measured on a macroscopic
scale, which shows the coatings bulk properties.
- Magnetron sputtering: in this PVD process,
the sputtering action is enhanced by intense magnetic fields.
- M alkalinity: Methyl orange alkalinity.
(See total alkalinity.)
- MAG: metal active gas welding process
usingcarbon dioxide (CO2) and argon (CO2) mixtures.
- Magnetic Particle Examination (MT):
a method of detecting cracks at or near the surface in magnetic alloys.
- Make-up: the water added to boiler feed
to compensate for that lost through exhaust, blowdown, leakage, etc.
- Manganese greensand: greensand which
has been processed to incorporate in its pores and on its surface the higher
oxides of manganese. The product has a mild oxidizing power, and is often used
in the oxidation and precipitation of iron, manganese and/or hydrogen sulfide,
and their removal from water.
- Manganese zeolite: synthetic gel zeolite
which has been processed in the same manner as manganese greensand, and used
for similar purposes.
- Manhole: the opening in a pressure vessel
of sufficient size to permit a man to enter.
- Manifold: a pipe or header for collection
of a fluid from, or the distribution of a fluid to a number of pipes or tubes.
- Material Safety Data Sheet (MSDS): information
sheet that lists any hazardous substance that comprises one percent or more
of the product's total volume. Also lists procedures to follow in the event
of fire, explosion, leak or exposure to hazardous substance by inhalation, ingestion
or contact with skin or eyes. Coatings manufacturers are required to provide
retailers with an MSDS for every product they sell to the retailer. Sales clerks
should make MSDS available to retail customers.
- Matrix: the continuous phase of a material
or coating in which separate
particles of another constituent are embedded. An example is tungsten carbide
particles embedded in a cobalt matrix.
- Maximum allowable working pressure:
the maximum gauge pressure permissible in a completed boiler. This pressure
is based upon either proof tests or calculations for every pressure part of
a vessel using nominal thickness exclusive of allowances for corrosion and thickness
required for loadings other than pressure. It is the basis for the pressure
setting of the pressure relieving devices protecting the vessel.
- Maximum continuous load: the maximum
load which can be maintained for a specified period.
- Maximum contaminant level (MCL): the
maximum allowable concentration of a contaminant in water as established in
the U.S. EPA Drinking Water Regulations.
- Mechanical bonding: usually represented
by mechanical interlocking of the deposited particles with the rough heights
on the substrate surface produced during grit blasting.
- Mechanical filter: a filter primarily
designed for the removal of suspended solid particles, as opposed to filters
with additional capabilities.
- Media: the plural form of "medium".
- Medium: a material used in a filter
bed to form a barrier to the passage of certain suspended solids or dissolved
- Mesa corrosion: mesa corrosion is one
of the common types of corrosion experienced in service involving exposure of
carbon or low alloy steels to flowing wet carbon dioxide conditions at slightly
elevated temperatures. An iron carbonate surface scale will often form in this
type of environment which can be protective rendering a very low corrosion.
However, under the surface shear forces produced by flowing media, this scale
can become damaged in a localized attack
produces mesa-like features.
- Metal dusting: accelerated deterioration
of metals in carbonaceous gases at elevated temperatures to forrn a dust-like
See thermal spraying.
- Metallurgical bonding: produced by diffusion
or chemical bonding between the coating and substrate.
- Methylene Blue Active Substances: chemical
compounds which react with methylene blue to form a blue compound which can
be used to estimate the concentration by measurement of the depth of color.
Substances measured include ABS and LAS types of detergents, thus the term is
commonly used as an expression of detergent concentration.
- Microbiologically Influenced Corrosion:
sometimes called Microbial Corrosion or Bio corrosion refers to corrosion that
is affected by the action of microorganisms in the environment.
- Micrograph: a micrograph is produced
when a section of the coating is taken, polished to show the particulate layers
and then photographed through a microscope.
- Microhardness: the hardness of a coating
as measured on a microscopic scale. Can show the hardness of individual phases
within the coating and avoid the effects of porosity.
- Micrometer (Ám): formally known as micron.
A linear measure equal to one millionth of a meter or .00003937 inch. The symbol
for the micrometer is Ám.
- Micron: See micrometer.
- Microstructure: the structure of a prepared
surface of a metal as revealed by a microscope at a magnification exceeding
- MIG: the metal inert gas (argon or other)
- Mil: One thousandth of an inch.
- Mill scale: the heavy oxide layer formed
during hot fabrication or heat treatment of metals.
- Mineral: a term applied to inorganic
substances such as rocks and similar matter found in the earth strata, as opposed
to organic substances such as plant and animal matter. Minerals normally have
definite chemical composition and crystal structure.
- Mineral acidity: Acidity due to the
presence of inorganic acids such hydrochloric, sulfuric and nitric acids, as
opposed to acidity due to carbonic acid or organic acids.
- Mineral spirits: paint thinner.
Solvent distilled from petroleum.
the potential of a specimen (or specimens in a galvanic couple) when two or
more electrochemical reactions are occurring simultaneously.
- MMA: the manual metal arc welding process.
- Moisture: water in the liquid or vapor
- Moisture in steam: particles of water
carried in steam, expressed as the percentage by weight.
- Moisture loss: the boiler flue gas loss
representing the difference in the heat content of the moisture in the exit
gases and that at the temperature of the ambient air.
- Molal solution: concentration of a solution
expressed in moles of solute divided by 1000 g or 1 kg
- Molar solution: aqueous solution that
contains 1 mole (gram-molecular weight) of solute in 1 liter of the solution.
- Mole: one mole is the mass numerically
equal (in grams) to the relative molecular mass of a substance. It is the amount
of substance of a system that contains as many elementary units (6.023 10^23)
as there are atoms of carbon in 0.012 kg of the pure nuclide C12.
- Molecule: the simplest combination of
atoms that will form a specific chemical compound; the smallest particle of
a substance which will still retain the essential composition and properties
of that substance, and which can be broken down only into atoms and simpler
- Moneypenny-Strauss test:
corrosion testing in a copper-sulfate
solution containing sulfuric acid. used to detect the susceptibility of stainless
steel to intergranular corrosion.
- Monomer: a molecule usually an organic
compound, having the ability to join with a number of identical molecules to
form a polymer.
- Most probable number (MPN): the term
used to indicate the number of microorganisms which, according to statistical
theory, would be most likely to produce the results observed in certain bacteriological
tests; usually expressed as a number per 100 ml of water.
- Mottle: (coating) a term often used
interchangeably with flooding or floating.
- MPN: the abbreviation for "most probable
- Muriatic acid: archaic term for hydrochloric
acid, HCl (acidum salis, marine acid, spirit of salt).