A-A-50557 Primer, Water-Borne, Acrylic or Modified Acrylic, for Metal Surfaces No S/S DocumentThis commercial item description covers a waterborne primer, acrylic or modified acrylic, suitable for use on exterior or interior metal surfaces. The primer is intended for use on properly prepared exterior and interior metal surfaces in non-marine environments including those where Volatile Organic Compound VOC emissions are controlled by air quality regulations as described below. The primer is intended to be used over bare metal with two coats of a waterborne topcoat, or over previously painted surfaces with one coat of topcoat. The primer should only be applied at temperatures between 50 degrees F 10 degrees C and 100 degrees F 38 degrees C and a relative humidity no higher than 85 percent.

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3.3  Quantitative requirements.

A-A-50557

3.3.1  Drying time.  The dry-to-touch time shall be a maximum of one hour, and the dry-to-recoat time shall be a maximum of 4 hours when tested in accordance with ASTM D 1640.

3.3.1.1  Testing conditions.  Unless otherwise specified, all tests shall be conducted using a dry film thickness of 0.001   0.0001 mils (0.25   0.02 mm) on a smooth steel surface prepared per type 3, procedure D of ASTM D 609.  All tests shall be run at room temperature as defined by ASTM D 3924.  The paint shall be allowed to dry for a minimum of 24 hours at room temperature.

3.4  Qualitative requirements.

3.4.1  Condition in container.  The primer, as received, shall be ready-mixed, and shall show no evidence of biological growth, livering, skinning, putrefaction, rust from corrosion of the container, or hard settling of the pigment.  Any settled pigment shall be readily dispersible in the liquid portion by hand stirring for five minutes to form a smooth, homogeneous product, free from persistent foam.  When stored for two weeks in either condition, 40   3   F (4.45 ±1.65 °C) or 100   3   F (37.77 ± 1.65 °C), the primer shall show no gelation, pigment settling, excessive thickening, coagulation, lumps, or coarse particles, and when applied to a glass panel shall dry to a smooth, uniform finish.

3.4.2  Color.  When tested in accordance with ASTM D 1729, the color shall be a general match to the color specified (see 7.2).

3.4.3  Working properties.  When tested as specified in ASTM D 2932, the primer coating shall brush and spray easily and dry to a smooth, uniform film, free from dusting, mottling, sagging, lap marks, color seperation, orange peel, or excessive brush marks.

3.4.4  Microbial growth resistance.  When tested in accordance with ASTM D 3273, the degree of microbial growth shall have not more than the maximum disfigurement rating of 8 as specified in ASTM D 3274.

3.4.5  Flexibility.  The primer coating shall not crack or flake when bent over a 0.125 inch (3.18 mm) diameter mandrel, as described in ASTM D 522.  The test shall be performed on a draw down of the primer coating on tinplate panels.  The dry film thickness shall be 0.0015

0.0001 inch (38   2   m).  The coating shall air dry for 24 hours and then conditioned for 2 hours at 221   F (105   C) prior to testing.

3.4.6  Adhesion.  When tested in accordance with ASTM D 3359 Method B, the adhesion shall be rated 4B or better.  Prepare the test specimen by applying the primer to a cold-rolled steel panel conforming to ASTM D 609, Type 1, prepared for coating by Method D.  Draw down a film of

the primer using a 0.003 inch (76   m) (approximately 0.006 inch (152   m) gap clearance) film applicator and allow to dry at room temperature for 72 hours.

3.4.7  Flash rusting resistance.  The primer shall exhibit  no flash rusting or rust bleed-through. After removing a portion of the dried primer with a suitable organic solvent the primer shall show

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