Table 4-4. Color Code
(b) Procedure The procedures for marking aluminum by painting are as follows:
Drycleaning solvent is flammable and solvent vapors are toxic. Use P-D-680, Type II
Solvent in a well-ventilated area. Keep away from open flames. Avoid prolonged
solvent contact with skin.
Clean all grease, dirt, and foreign matter from the surface to be painted using drycleaning solvent,
Federal Specification P-D-680.
Paint each item with parallel stripes of equal width, 1/2 to 3/4 inch wide, placed side by side and i
sequence so that when read from nearest end of bar towards the middle, the material designation is shown in figure 4-1.
Cross-reference of old and new color code is presented in table 4-5.
Leave a space between the stripes of not more than 1/4 inch, when two or more like colors appear
adjacent to each other.
Leave a space of 3/4 to 1 inch between basic color number stripes and temper and strain hardening
(8) Types. Aluminum alloy types are listed in table 4-6.
Handling. In some instances, serviceable aluminum alloy parts and sheet have been disposed of due to lack
of knowledge by inspection personnel as to the effect of various depth scratches on the strength and corrosion resistance
of clad alloy. Also, attempts have been made to remove scratches from aircraft skin by sanding, buffing, or polishing,
resulting in removal of much of the cladding material and causing decrease in strength and corrosion resistance.
Assemblies fabricated from clad aluminum alloy sheet will not be rejected by inspection personnel, unless the defect is of
sufficient depth to adversely affect the mechanical properties or cover sufficient area to impair the corrosion resistance of
the assembly. Scratches or abrasions that do not penetrate the cladding will not affect corrosion resistance. Scratches
resulting from normal handling and processing of clad aluminum alloy sheet rarely extend through the cladding to
penetrate the core.
Do not attempt to remove scratches or other surface defects by sanding or buffing.
Such operations remove the protective layer of cladding.
(1) Effects of scratches. Scratches of various depths have different effects on clad aluminum alloys. Some
scratches remove enough of the cladding materials to cause a decrease in strength and corrosion resistance.