Table 4-6. Aluminum Alloy Types - CONT
Seamless Tubing, Round, Square, Rectangular and Other Shapes - continued
F (As Fabricated)
6061 (61S) and
6061 (61S) and
(2) Allowable defects. The following surface defects do not affect strength or corrosion resistance:
Scratches that penetrate surface layer but do not extend beneath cladding.
Small corroded areas that do not extend through cladding, or into core material.
(3) Harmful scratches. Scratches which extend through cladding and penetrate core material create stress
concentrations. These stress concentrations will cause fatigue failure when the part is highly stressed or subjected to
repeated stress reversals. Use sheet in this condition for nonstressed applications.
(4) Testing. A spot test is a convenient method of determining whether or not a scratch extends through
cladding to core. Procedures for performing a spot test 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.
(a) Clean and degrease sheet with drycleaning solvent, Federal Specification P-D-680.
(b) Prepare a caustic solution of 10 percent (by weight) of sodium hydroxide, Federal Specification 0-S-598,
(c) Place a drop of solution on part of the scratch, and allow 5 minutes for solution to react.
(d) Rinse solution away with water and allow sheet to dry.