MIL-STD-171F
4. GENERAL REQUIREMENTS
4.1 Materials. All materials used shall conform to the requirements of the applicable specifications. Types, classes, grades, etc., shall be specified on the part drawing by the procuring activity. Materials may be subject at any time to such tests of the pertinent specification as the procuring activity shall prescribe to determine compliance with the applicable specification.
4.1.1 Applicable documents. The specifications and standards referenced in this document shall be the issue in effect on the date of invitation for bids. The finish or system requirement in the tables does not indicate the latest document designation as evidenced by the omission of the revision letter following the document number. *
4.2 Substitution for specified finishes, processes, or materials. If, because of special conditions of service or design, the contractor considers that a finish, method, or material, other than that specified herein, is necessary or more suitable, such finish, method, or material may be used upon written approval of the contracting officer. Unless otherwise specified, the contractor shall demonstrate the suitability of the proposed substitute by submission of samples, test specimens, test data or other evidence as required by the procuring activity.
4.3 Preparation and cleaning of surfaces. Before any plating, metal conversion or painting, all surfaces shall be free from soils and corrosion; for example, grease, oil, solder flux, welding flux, weld spatter, sand, rust, scale, and all other contaminates that might interfere with the intimate application of the finish. Cleaning shall be done immediately before the finishing operation, or suitable precautions shall be taken to ensure that the surfaces remain clean until they are to be finished. When a cleaning procedure is not specified by the procuring activity or as a part of the applicable finish specification, the supplier shall use any cleaning procedure which will produce a clean surface and not adversely affect the surface being cleaned, or the subsequently applied coating.
4.3.1 Castings. Porous castings may require sealing to assure that they are leakproof, and to prevent bleeding-out of treating chemicals which would cause staining or corrosion of the metal surface and damage to the finishing system. Impregnation or sealing of castings should be accomplished after machining and complete removal of oils, greases, and other surface contaminants. Reference should be made to MIL-STD-276 or MIL-I-13857, as applicable.
4.4 Drainage of processing solutions from parts. Where possible, finishing of parts shall be done prior to assembly. For example, aluminum sheet to be lap-seamed or riveted should be anodized prior to the joining operation. Where this is not possible the finishing and fabrication of items shall be handled in such a way that processing solutions shall not become trapped within any part of the assemblies such as lock seams, lap joints, spot welds, rivets, bolts or other places where processing solutions will remain on the part.
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