01 March 2005
to be protected. As the current passes to the metal,
Atomization - The formation of tiny droplets of liquid, as
corrosion is suppressed.
in the paint spraying process.
Catalyst - The component of a two-part curing-type
Austenitic - A form of stainless steel that is essentially
sealant that causes the polymer to react.
nonmagnetic and not hardenable by heat treatment.
Austenitic stainless steels have the highest corrosion
Caustic Embrittlement - Aluminum and its alloys are
rapidly attacked by even dilute alkali solutions. The
result of the combined action of tensile stress and
corrosion due to the alkali solution causes caustic
Base Compound - The major component of a two-part
curing-type sealant that contains the polymer (usually
Cavitation - The sudden formation and collapse of low
referred to as Part B).
pressure bubbles in a liquid stream by means of
mechanical forces. Cavitation is often encountered
Bilge - The lowest point of an aircraft's inner hull. This
area is where cable runs, wire bundles, coaxial cables,
lights, and antennas are typically installed.
Cell - In corrosion processes, a cell is a single unit of
electrolysis that is responsible for corrosion. It consists
Bleeding - A defect in which pigment from a lower coat
of an anode and a cathode immersed in an electrolyte
of paint diffuses into an upper coat and discolors it.
and electrically joined together. The anode and cathode
may be two separate metals or dissimilar areas on the
Brush Coat - The thin coating of sealant usually applied
over fasteners, seams, and various parts and small
exposure to the environment that results in a powdery,
chalky residue on the painted surface.
Capillary Action - The action by which the surface of a
Channel Seal - A seal formed by injecting a noncuring
liquid, in contact with a solid, is raised or lowered. This
sealant material into a groove machined in one faying
is caused by the relative attraction of the liquid molecules
surface of the mating or overlapping structure after
for each other (surface tension) and those of the solid.
The "wicking" of a fluid up a cloth is an example of
Checking - Fine cracks in a surface film due to excessive
shrinkage of the film or expansion of the surface.
Carbonize - To reduce or convert into carbon, usually
by high heat or partial burning.
Chemical Conversion Coating - A chemical treatment
of a metal surface, such as aluminum or magnesium,
Cathode - The negatively charged electrode of an
which results in a protective (corrosion resistant) layer
electrolytic cell, where the action of the corrosion current
on the metal's surface. Types of application include
causes a reduction reaction. This results in the nearly
immersion, brushing, or spraying with the selected
complete elimination of corrosion.
chemical solution. Coatings covered by MIL-C-5541
are examples. The protective layer also greatly enhances
Cation - A positively charged ion of an electrolyte which
migrates toward the cathode. Metallic ions, such as iron
or copper, are cations.
Chlorides - Certain compounds of chlorine that are
extremely corrosive. Most pitting corrosion is associated
Cathodic Protection - Corrosion protection achieved
with chlorides. Many varieties are present in seawater
by supplying electrons to the metal to be protected. The
and contribute to making seawater corrosive.
source of the protective current may be a sacrificial
metal, such as magnesium, zinc, or aluminum, which
creates a galvanic coupling. The current may also be
supplied by a power source (rectifier, generator, or
battery) attached to an appropriate anode and the metal