TT-C-490 Chemical Conversion Coatings And Pretreatments For Metallic Substrates Base For Organic CoatingsThis specification covers processes, pretreatments, and pre-primer surface preparations of metallic substrates for coating applicators. It covers metal surface preparation for delaying corrosion initiation and promoting primer adhesion. In addition, this specification covers the testing requirements for qualification of conversion coatings, the pretreatments and pre-primer coatings.

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TT-C-490F

TABLE II. CARC approved primers - Continued.

Specification	Dry film thickness	Substrate 1/	ASTM B117 (hours)	GMW 14872 (cycles)
MIL-DTL-53022, type IV	1.3 - 1.7 mils	CRS and AL	1,000	40
MIL-DTL-53030, type II	1.3 - 1.7 mils	CRS and AL	1,000	40
MIL-DTL-53084	0.8 - 1.2 mils	CRS and AL	1,000	-
A-A-59745	2.5 - 3.5 mils	CRS	-	120
MIL-PRF-85582	0.6 - 0.9 mils	AL	2,000	-

1/ Aluminum (AL) and cold rolled steel (CRS).

TERMS: 1 mil = 25.4 microns.

4.8 Qualification testing of pretreatments. Tests specified in 4.8.1-4.8.11 pertain to the chemical and coating suppliers submitting products for qualification to types III, IV and VIII.

4.8.1 Test conditions. Except as otherwise specified herein, the routine testing and referee testing shall be conducted in accordance with ASTM D3924. The dry film thickness of the epoxy primer being used in this testing shall be as specified in 4.8.4. Failure of any test result to fall within the specified ranges in section 3 shall constitute failure of the applicable test.

4.8.2 Test specimens/coupons. Steel test specimens/coupons shall be cold rolled SAE 1010 steel conforming to ASTM A109/A109M or ASTM A1008/A1008M. Hydrogen embrittlement coupons shall be type 1e as described in ASTM F519. The specimens/coupons shall have Rockwell B hardness (HRB)

55 to 75 and a surface roughness of 30 to 45 micro inches (arithmetic average) as rolled. Aluminum test specimens/coupons shall be aluminum alloy 2024-T3. Standard steel and aluminum test specimens/coupons shall be 3 x 6 x 0.0312 inches in size, except as specified herein.

4.8.3 Test procedures. Tests shall be conducted in accordance with ASTM, GM, or as specified herein (see 4.3). The right is reserved to make any additional tests deemed necessary to determine that the pretreatment meets the requirements of this specification.

4.8.4 Epoxy primer. Test specimens/coupons shall be prepared with the appropriate pretreatment that is being tested. These test specimens/coupons shall be solvent wiped and cleaned prior to applying epoxy primer. Apply epoxy primer conforming to MIL-DTL-53022, type IV or MIL-DTL-53030, type II to a dry film thickness of 1.5 ± 0.2 mils (37.5 ± 5 microns). For aviation system application evaluation,

MIL-PRF-23377 or MIL-PRF-85582 epoxy primers shall be used and applied to a dry film thickness of

0.6 - 0.9 mils (15 - 22.5 microns).

4.8.5 Storage stability. Along with the submission of the samples for testing, the manufacturer shall provide a statement describing the storage life of the material, the conditions for storage and the containers for storage. Check for compliance with 3.6.1.