T O. 1-1A-9
Complete qualification and requalification requirements are cited in Specification MIL-W-6858.
2-193. CLEANING/PREPARATION FOR SPOT WELDING. The surface of parts to be spot welded shall be free of
paint, oxides, scale, ink, grease, dirt, or other contaminates detrimental to the welding process.
2-194. Cleaning of individual (separate) parts may be accomplished by one/combinations of the following methods: a.
Immersion cleaning with Specification P-C436, prepared by dissolving 10-12 ounces of compound per gallon of water
and heated to 2000 and 2120F.
Immersion will vary in accordance with type of contnmin2rlts to be removed. Ordinary soils, etc., require 6-10
Paint can be removed by immersion in paint and varnish remover Specification MIL-R-7751 (see T.O. 1-1-2 and
1-1-8 for preparation/application). Spot paint removal can be accomplished by application of MIL-R-25134.
Spray-wash with compound with Specification MIL-C-5543 or Specification P-S-751 (see T.O. 1-1-1 and 1-1-2
for preparation/application of solution).
Vapor degreasing with trichloroethylene, Specification MIL-T-7003 (aircraft parts) or Specification MIL-T-27602.
Trichloroethylene solvent produces dangerous and toxic fumes. Do not breath fumes for
prolonged periods. Use adequate ventilation. When using solvents, alkllne solutions acids,
etc., wear approved clothing, acid/solvent resisting gloves, aprons/ coveralls, and face
respirators. If solutions are splashed into eyes, flush thoroughly with water immediately and
then report to the dispensary. For additional instructions contact local safety officer.
If parts are to be used in areas of oxygen storage and transfer systems and on surfaces of
missiles using liquid propellant, do not use dry cleaning solvent or solvent that is not
compatible. In addition, such parts shall be cleaned as specified (see T.O. 42C-1-11 and T.O.
00-25-223). Failure to observe these precautions can result in serious or fatal injury to
2-195. After grease, oils, dirt, etc., are removed by one of the above methods and parts are rinsed in hot water, material
with heavy oxides and scale shall be cleaned by one of the following methods as applicable:
Parts (300 series chromium-nickel grades) in which acid solutions can not be trapped and are readily rinseable,
may be cleaned by mixtures of nitiric and hydrofluoric acid in water. The correct percentage content of the two acids for
a given oxide/scale removal job shall be determined by testing. Make test panel (1" x 4")of the same material as that of
part being cleaned and process through complete cleaning and descaling cycle. The part is then inspected to determine
if it is clean and for etching, intergranular attack, or excessive metal loss which would cause component to be
condemned. The acid concentration, immersion time or solution temperature is then adjusted until required results are
obtained. The procedures controls, etc., must be established by competent operators trained in the handling of
chemicals and metal inspection. Solutions acid content for the removal of heavy scale may be from 5 to 25% nitric acid
and from 1/2 to 3% of hydrofluoric acid by volume. For light scale acid varies from 10 to 15% nitric acid and 3/4 to 1-
1/4% hydrofluoric. For heavy oxides the percentage of hydrofluoric may have to be increased to 3%by volume. Bath
temperatures are normally maintained at 120°-140°F.
The more nitric acid present in portion to hydrofluoric the less rapid the action will be.
Conversely, the higher the percentage of hydrofluoric in proportion to the nitric acid, the more
rapid the action will be. Table 2-18 shows the effect of the adjustable variables on the action
(descaling) of the solutions. From this table, it can be readily determined that the nitric acid
inhibits the action of the hydrofluoric.