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

3.3.3.7  Method VII - steam cleaning. Steam cleaning shall be followed with methods II, III, or IV to achieve a water-break free surface (see 4.7.3.1). Substrates that are steam cleaned shall pass the water break test as described in 4.7.3.1.

3.4  Types of conversion coatings, pretreatments and pre-primer coatings.

3.4.1  Type I. Type I coatings shall be applied by spray or immersion and have coating weights in the range of 300 - 500 mg/ft2 (1.5 - 5.0 g/m2). When painted, all corrosion and testing within this document applies.

3.4.2  Type II. Type II coatings shall be applied by spray, steam, immersion or hand wiping and have a minimum coating weight of 35 mg/ft2  (3.5 g/m2). When painted, all corrosion and testing within this document applies.

3.4.3  Type III. Type III coatings shall contain greater than 50% organic compounds by weight in the dried film, such as wash primers, adhesion promoters and flash-rush inhibitors as defined by the manufacturer of the coating. When painted, all corrosion and adhesion testing within this document applies. With the exception of wash primer conforming to DOD-P-15328 and MIL-C-8514, all products under this type shall be Cr6+  free and shall require product qualification.

3.4.4  Type IV. Type IV coatings shall contain greater than 50% inorganic compounds by weight in the dried film, such as conversion coatings, adhesion promoters, and flash-rust inhibitors, as defined by the manufacturer of the coating. When painted, all corrosion and adhesion testing within this document applies. Product qualification required for this coating type.

3.4.5  Type V. Type V coatings are the same as type I coatings except that the coating weight is in the range of 500 - 1100 mg/ft2  (5.0 - 11 g/m2). When painted, all corrosion and testing within this document applies.

3.4.6  Type VI. Type VI coatings shall be validated for performance using MIL-DTL-5541. Whenever one of the coating types is not cited in a relevant contractual document or drawing, select the type II coating in MIL-DTL-5541.

3.4.7  Type VII. Type VII coatings shall be validated for performance using MIL-A-8625, Anodic Coatings for Aluminum and Aluminum Alloys. When painted, all corrosion and adhesion testing within MIL-A-8625 applies.

3.4.8  Type VIII. Type VIII coated surfaces shall be abrasive blast cleaned. These coatings are classified as metal-rich finely divided metal powder, including ethyl silicates, alkyl silicates, potassium silicates, and metal-rich polymer coatings. When painted, all corrosion and adhesion testing within this document applies. Product qualification required for this coating type. In accordance with MIL-DTL-53072, a sealer coating of MIL-DTL-53022 or MIL-DTL-53030 shall be applied over the zinc-rich primer.

3.5  End item requirements. The following requirements shall apply to the applicator of the coating systems. All test specimens/coupons shall be produced in the same manner as the end item.

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