2. Apply a coat of vinyl to protect the first primer
screws to cover all exposed threads, remove
coat as soon as practicable.
suspension lugs, and fill lug holes with rags.
6. Use only sand or black grit (mineral grit) of 40 to
CAUTION
80 mesh.
Phosphoric acid is highly corrosive. Wear goggles, a
7. Use an abrasive only once.
rubber apron, and chemical-resistant rubber gloves
8. Do NOT sandblast in the immediate area of the
when handling acid. Read the material safety data
filling hole cover.
sheet (MSDS), available from your supervisor,
before handling or using phosphoric acid.
9. Do NOT sandblast flange or sealing areas.
ALUMINUM SURFACES
EXTERNAL THERMAL-COATED
SURFACES
Aluminum, in its pure state, is very resistant to
corrosion, but it is too soft and weak for most
Bombs missing more than 7 square inches of
applications. Therefore, aluminum alloys are used in
thermal coating are not considered to be thermally
the manufacture of the Mine Mk 67, as well as some
protected and, therefore, are restricted from issue to
mine components, such as actuation counters, clock
aircraft carriers. Bombs missing less than 7 square
delays, and flight gear. These are all subject to
inches can be repaired by using a putty knife or a cold
corrosive attacks.
chisel and a hammer to remove any unbonded coating
Corrosion is most severe when moisture is present
from the bomb body.
or when the aluminum is in contact with another type
Particular attention should be given to the forward
of metal or with another type of aluminum alloy. The
end. If the coating is unbonded, it comes off in chunks.
first indication of corrosion is the appearance of white
If the coating is bonded, it comes off in small chips and
powdery residue in the area of contact. Later, pitting
a residue is left on the bomb. Remove the coating in all
and scoring of the aluminum surface are evident.
directions from the unbonded coating until the bonded
Finally, the aluminum deteriorates completely.
coating is reached. Bombs with minor chips, cracks,
Use an abrasive cloth to remove corrosion from a
and so forth, that are not rejected must have areas
painted aluminum surface. Then clean the surface with
where the coating is missing touched up with primer.
a cleaning compound solvent, prime with zinc
On the Mk 65 mine, the thermal coat is
chromate, and repaint with applicable paints as listed
epoxy-based with asbestos or ceramic fibers. Do not
in chapter 2 of NAVSEA SW550-AA-MMI-010.
sand or make dust. The surface can be cut or shaped
STAINLESS STEEL SURFACES
with a knife to define the repair area. Remove the
m i n i m u m p o s s i b l e a m o u n t o f m a t e r i a l . We a r
Stainless steel is an alloy of steel and chromium.
safety-approved organic vapor respirators, goggles,
The chromium helps to prevent corrosion. Stainless
and gloves when using solvents or paint or when
steel is used in manufacturing the Mine Mk 56 and its
applying a thermal coat. Repair the mine according to
Mk 2 instrument rack. The surface of the metal has a
the instructions in NAVSEA SW550-AA-MMI-010.
tendency to pit when it is exposed to a marine
environment. Corrosion on stainless steel is indicated
PAINTING OF MINES
by either a rough surface or a red, brown, or black stain.
Painting is the process of applying coats of paint to
Use an abrasive cloth or a power tool to remove
surfaces, primarily for the preservation of the surfaces.
corrosion from stainless steel. After you remove the
It seals the pores of wood and steel, arrests decay, and
corrosion, you may need to apply a primer. This can be
helps prevent the formation of rust and other types of
done in the following two steps:
corrosion.
1. Apply a solution of phosphoric acid and resin.
Basically, a paint job consists of one primer coat
(This application coats the surface with a plastic
and one or more finish coats. The primer coat is the first
fi l m t h a t i m p r ove s t h e a d h e s ive n e s s o f
coat applied to a properly prepared and cleaned
surface. It improves the adhesiveness of the outer, or
subsequent primer coats.)
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