Section IV. SPECIAL PROCEDURES FOR MAGNESIUM

TM 750-245-4

satisfactory hiding power, color, gloss, and smoothness.

Criteria are:

If the surface does not meet these requirements, it

(1) Major items must be the correct color in

should be repainted. Removing the existing paint may

accordance with applicable system documentation.

not be necessary.

(2) The correct color of items disassembled

(7) Exterior surfaces or trailers, vans,

from major items shall be recorded on the inspection

antennas, interior walls and ceiling of vans, and

tag.

surfaces of cabinets and consoles shall be smooth,

(3) There shall be no dried overspray, runs,

continuous and like new. Touch up or spot painting will

sags, blisters, dirt, grit, orange peel, or other

be allowed for areas of up to 1/2-square foot.

imperfections. The imperfection shall be removed and

b. Finishing. The inspector should inspect the

the local area repainted.

items requiring a finish. Items requiring painting after a

(4) There shall be no peeling, flaking, or other

finish coat should be inspected in accordance with

evidence of poor adhesion. When poor adhesion is

paragraph a above. The inspector will ascertain that the

indicated, the paint on the entire surface must be

item meets the required standards and is ready to be

removed and the surface cleaned and repainted.

returned to the using organization.

(5) The painted items shall be examined for

(1) shall be smooth, fine grained, adherent

adhesion after the coated items have dried for a

and free from visible blisters, pits, nodules, porosity,

minimum of 24 hours for quick-drying and baking

indications of burning, excessive edge build-up and

systems, and for a minimum of 72 hours for all other

other detrimental defects. Superficial staining shall not

systems. Water-resistant, pressure-sensitive adhesive

be cause for rejection.

tape (3/4-inch wide) shall be used. Press a 2-inch

(2) Slight discoloration from baking will not be

length of a somewhat longer piece firmly onto a flat or

cause for rejection.

cylindrical surface of the item, rubbing out all air bubbles

under the tape. Allow approximately 10 seconds for the

(3) Cadmium plating should have no white

test area to return to room temperature. Grasp a free

corrosion products on the surface. Bright or dull finish is

end of the tape and at a rapid speed, strip it from the

acceptable.

item by pulling the tape back upon itself at 180 degrees

(4) Presence of black-silver oxide or silver

(in such a manner that the tape is folded back-to-back

sulphide (tarnish) shall not be cause for rejection of

during the procedure). Observe for bare spots where

silver-plated items.

the paint is removed. Disregard flecks of paint on tape

(5) All coatings shall be visually checked for

where the underlying metal or phosphate coating is not

continuity and uniformity.

visibly exposed.

(6) Any items which reveal bare spots due to

(6) Paint

shall

have

uniformity

and

some contamination must be completely reworked.

Section IV. SPECIAL PROCEDURES FOR MAGNESIUM

2-12. Facilities

2-11. General

All treatment equipment should be inspected at random

a. The cleaning, finishing, and painting of

by the quality control inspector. The inspections are

magnesium is covered in this section because of its

made to determine that the equipment and facilities for

unusual characteristics.

cleaning, treating, and painting of magnesium are

b. Magnesium is a silver-white, light, malleable

adequate. He also should insure that proper safety

ductile, bivalent, metallic element that occurs

equipment is available. If samples of treatment solution

abundantly in nature. It is used in metallurgical and

are taken which reveal inadequate solutions or safety

chemical processes, photography and signaling

hazards, corrective action must be taken immediately by

equipment. It is highly flammable, and is a good

the inspector.

pyrotechnic because of the intense light it produces on

burning. Structurally, it is used as an alloy.

2-13. Magnesium Cleaning

c. The material must be treated with certain

a. Acid is used to clean magnesium by pickling or

finishes to prevent excessive corrosion, indicated by a

to remove oxide layers of old chemical finishes, burned

powdery substance. Special and cautious techniques

on drawing and forming lubricants and other water-

must be utilized while machining or cleaning this metal

insoluble or non-emulsifiable substances.

due to its highly flammable composition. It is often used

in design, when weight limitations are imperative.

2-3