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 coating adhesion and minimize the possibility of defects such as blistering, peeling, flaking, and under film
rusting. Surfaces to be painted for preservation must be completely free of mill scale, rust, loose paint,
dirt, oil, grease, salt deposits, and moisture. To prevent embedding contaminants during surface
preparation, oil or grease must be removed before using power tool or abrasive-blast surface preparation.
Rusted surfaces shall be freshwater rinsed, where practicable, to remove water-soluble contaminants
before abrasive blasting or additional surface preparation by other means. Weld spatters and flux
compounds should be removed by grinding or chipping.
a. All exterior hull surfaces and floodable tanks shall be pressure washed 1500 to 2500 PSI prior to
mechanical cleaning or blasting to remove salts and chlorides. This will prevent contamination of the new
paint system.
b. Removing Old Paints. In touchup painting for preservation, when only localized areas or spots need
attention, removal of old paint must go beyond the visibly defective areas until an area of intact and
adhering paint film is attained, with no rust or blisters underneath. The edges of tightly adherent old paint
remaining around the area must be tapered (feathered) to allow proper blending and prevent laying new
paint over loose or cracked paint. When painted surfaces show evidence of corrosion, peeling, blistering
checking, scaling, or general disintegration, the paint is to be removed down to the bare surfaces.
c. Preparing Old Paint in Good Condition. Old paint in good condition provides an excellent base for
repainting. When a surface is to be repainted and the old paint is not to be removed, the surface shall be
roughened with an abrasive, cleaned, and dried before new paint is applied. Roughening may be omitted
when hydro blasting of underwater hull areas results in clean vinyl anti-fouling paint showing the original
red or black color. Roughening may also be omitted where painting is being done for appearance, rather
than preservation, and some peeling or flaking can be tolerated.
metallic surfaces for painting. If abrasive blasting is not specified or permitted, mechanical means shall be
used. If the surface to be painted is subject to flash rusting, blast-clean only the area that can be coated
with paint immediately, before flash rusting can occur.
a. Steel Surfaces. When blasting to bare steel is specified or required, surfaces shall be cleaned to
near-white condition, as prescribed in paragraph 3-17.b. Near White Metal Blast.
b. Aluminum Surfaces. Aluminum surfaces shall be cleaned free of corrosion products, dirt, and other
contaminants by light abrasive blasting. Use of 80-grit aluminum oxide or garnet abrasive at 65
lb/in2pressures has resulted in satisfactory aluminum surface preparation, with minimum metal removal.
NOTE
The abrasive sanding discs used on aluminum must not have been used previously on other
metals or to remove copper or mercury pigmented paints.
c. Spot Cleaning. Spot cleaning after blasting can be done by power brushing or orbital sanding. For
cleaning aluminum, only use clean dry sand, stainless steel wire brushes, stainless steel pads, or
abrasive sanding discs. If the cleaned aluminum surface is not painted immediately or becomes
contaminated with oil or grease, the surface shall be washed with a liquid detergent cleaner, rinsed with
fresh water, and allowed to become completely dry before paint is applied.
3-6. Plastic Surfaces. Plastic surfaces requiring painting shall be lightly roughened. All extraneous
matter shall be removed by washing with detergent, rinsing, wiping with a solvent, or by other suitable
means. Glazed surfaces shall be sanded to promote adhesion.
3-7. Surface Cleaning Methods. The goal of surface cleaning is to provide a roughened surface, which
is free of contamination and gouges or sharp projections. Roughening is necessary to attain the
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