generally occurs at a stress far below the fatigue limit in
a laboratory environment, even though the amount of
corrosion is very small. For this reason, protection of
all parts subject to alternating stress is particularly
important wherever practical, even in environments that
are only mildly corrosive.
PREVENTION AND CONTROL
Much has been done over the years to improve the
corrosion resistance of newer Navy warships.
Improvements include the selection and combination of
materials of construction, chemical surface treatments,
insulation of dissimilar metals, and protective paint
finishes. All these improvements are aimed at reducing
maintenance as well as improving reliability. Despite
refinements in design and construction, corrosion
control is a problem that requires a continuous
With this idea in mind, the NAVSEASYSCOM has
developed some excellent ship class corrosion control
manuals for you to use as reference tools aboard ship.
There are two manuals a GS supervisor should read.
They are the Corrosion Control and Prevention Manual
f o r
D D - 9 6 3
c l a s s
N A V S E A
S9630-AB-MAN-010, and the Standard Corrosion
Control Manual, NAVSEA S9630-AE-MAN-010.
As a leading petty officer or work center supervisor,
one of your most important aids in the prevention and
control of corrosion is an adequate cleaning program.
The term clean means to do the best job possible using
the time, materials, and personnel available. A daily
wipedown of all machinery is better than no cleaning at
all. The importance of frequent cleaning cannot be
overemphasized. Any cleaning procedures, however,
should be in the mildest form possible to produce the
desired results. For example, spraying water around
multipin connectors can cause electrical shorts or
grounds, with a possible loss of control functions or
In general, gas turbine engines and enclosures
should be cleaned as often as necessary to keep surfaces
free of salt, dirt, oil, and other corrosive deposits. A
thorough inspection and cleaning of gas turbine intakes
and enclosures should always be done in conformance
with PMS requirements.
These cleanings and
inspections should be done before getting underway,
after an extended stay in port, and after returning to port
from an extended time at sea.
Since marine gas turbines are more subject to
internal corrosion than engines used in other types of
applications, internal cleaning is of particular
importance. This is accomplished by means of water
A mixture of B & B 3100 water-wash
compound and distilled water is injected into the engine
air inlet while it is being motored and then rinsed with
distilled water in the same manner. It is then operated
for about 5 minutes to remove all liquid. For more
detailed information on this procedure, consult the
applicable PMS card.
Characteristics of Metals
As a GS supervisor, you should have a thorough
knowledge of the characteristics of the various metals
used throughout the engineering plant, as well as the
To some extent, all metals are subject to corrosion
To keep corrosion to a minimum, corrosion-resistant
metals are used to the fullest extent possible consistent
with weight, strength, and cost considerations. On
exposed surfaces, the major preventive for providing
relative freedom from corrosion is a coating of
protective surface film. This film can be in the form of
an electroplate, paint, or chemicaI treatment, whichever
is most practical.
Most of the metals used in the engineering plants
require special preventive measures to guard against
corrosion. In the case of aluminum alloys, the metal is
usually anodized or chemically treated and painted.
Steel and other metals such as brass or bronze (with the
exception of stainless steels) use cadmium or zinc
plating, protective paint, or both. In all cases, the
protective finish must be maintained to keep active
corrosion to an absolute minimum.
DEPRESERVATION OF GAS TURBINE
The main purpose of engine preservation is to
prevent corrosion of the various types of materials that
make up the engine and its accessories. Preservation
also ensures against gumming, sticking, and corrosion
of the internal passages.
Engine preservation and depreservation is vital
because the corrosion of engine structures can and does
have a great effect on the operational and structural
integrity of the unit. Therefore, it is important that you
know about methods of preservation, materials used,
and depreservation procedures.