Method 3 substrate examination and evaluation the

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Method 3: Substrate Examination and Evaluation The test methods are as described in the Steel Structures Painting Manual . 1. Vol. 1, Chapter 6, pp.201-202, Tooke gage examination through a 50X internal microscope. 2. Vol. 1, Chapter 6, pp.200. Coating inspection requirements specify use of a minimum 30X power pock- et-sized microscope to examine the coating field evaluations.
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SYSTEMS PAGE 48 Method 4: Dry Film Thickness Testing The gages that may be employed include: 1. SSPC-PA 2 (Type 1 gages), SSPC Method for Measurement of Dry Film Thickness with Magnetic Gages; Steel Structures Painting Manual , Vol. 1, Chapter 6, pp.198-200. 2. SSPC-PA 2 (Type 2 gages), SSPC fixed probe or magnetic flux gages; Steel Structures Painting Manual , Vol. 1, Chapter 6, pp.201-202. Method 5: Coatings Cure Evaluation ASTM D1640, Test Methods for Drying, Curing, or Film Formation of Organic Coatings , is specified as a recom- mended field method. Field evaluation of coating cure is generally difficult because there are no universally reli- able filed tests for such purposes. Solvent rub tests, sandpaper tests and microscopic examinations can be uti- lized in field testing. If field testing results are inconclusive, coating samples can be taken for extensive laboratory analysis. Compatibility of Overcoating System Prior to selection of materials to overcoat existing coatings, the recommendations of the manufacturers of pro- posed overcoatings should be solicited. Paints that will cause "lifting" of the existing coating must not be allowed. The compatibility testing of the competitive materials shall be conducted in accordance with ASTM D5064, Standard Practice for Conducting a Patch Test to Assess Coating Compatibility , and the following (if different sys- tems are present on different parts of the structure, each system must be tested): A 12-in. diameter section in the middle of the test area shall have the existing coating removed to bare steel (SSPC-SP 11). The edges of the bared area are to be feathered using power tools. This area shall be primed with the selected paint(s) to determine if the primer lifts the edges off the existing paints. Apply candidate coatings by proposed method of application to the entire test panel area. (The top coat(s) should be applied to the primed area in accordance with the manufacturer's recommendations.) Inspect surface after the coating is fully cured (7 days or 2 weeks at 77° Fahrenheit [25°C] and 50 percent rela- tive humidity) for signs of lifting, wrinkling, cracking or other film defects. If time permits. The evaluation period should be extended beyond exposure to the first "deep freeze" to ensure compatibility of the topcoat. Only coatings exhibiting no peeling or removal (Scale 5A of ASTM D3359) will be allowed. Degradation—Because existing paint systems may degrade rather rapidly, the tests specified above should be conducted no more than 180 days prior to the beginning of work to ensure that the decision on scope of work (e.g., spot painting versus total removal) is still valid.
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