Home>ASTM Standards>ASTM D5064-16a(R2021) pdf free download

ASTM D5064-16a(R2021) pdf free download

ASTM D5064-16a(R2021) pdf free download.Standard Practice for Conducting a Patch Test to Assess Coating Compatibility
1. Scope
1.1 This practice covers the procedures for assessing coat- ing compatibility when maintenance of an in-place coating system is being contemplated. It does not address procedures for assessing the integrity of the existing coating to determine if it can be repainted, nor does it establish the compatibility of the maintenance coating system with the substrate or corrosion products. The practice is intended for use in the field. SSPC-TU 3 discusses the risks associated with the mainte- nance painting practice known as overcoating. N OTE 1—Pass-Fail Criteria (for example, adhesion requirements) are not established by this practice. These should be established by the user or specifier with input from the coating manufacturer. 1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.4 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
6. Procedure
6.1 Select test locations for evaluation that adequately characterize differences in configuration of the structure and the exposure environment; that is, vertical versus horizontal surfaces; sheltered versus unsheltered exposure; atmospheric verses splash zone or immersion. Additional factors must be considered for previously immersed areas. For these cases consult the coating manufacturer. A minimum of three test locations with one test patch in each is recommended. 6.2 The size of each test patch is limited by the size and configuration of the test locations. Each test patch shall be as large as possible, with a minimum size of 1.0 m 2 (10.8 ft 2 ) recommended. 6.3 Prepare the surface of the test areas using the methods specified for the maintenance painting procedure (Note 2). Alternative methods of preparation may also be evaluated in separate, adjacent tests. N OTE 2—This practice is intended to assess compatibility with the existing coating only and does not apply to areas where the substrate is exposed by the methods of preparation. 6.4 Measure the existing coating thickness in accordance with Test Methods D6132, D4138, or Practice D7091, as appropriate for the type of substrate. 6.5 Measure the air and surface temperatures, the relative humidity and the dew point temperatures and verify that the conditions are within the limits recommended by the coatings manufacturer for the product(s) being tested. 6.6 Apply the test coating to the thickness recommended by the coating manufacturer. Use the application technique as intended for use during production operations. If agreed upon between the purchaser and the seller, the method of coating application may be different from that proposed for use on the job, that is, brush application of the test patch even though spray application is intended to be used on the job. However, this can cause anomalies in the data and is not generally recommended.6.7 Immediately after application, measure the wet-film thickness in accordance with Practice D4414. Inspect each patch for application defects such as runs, sags, and pinholes. If such defects cannot be corrected as a part of the initial application process, prepare a new test patch. 6.8 After the coating has dried, measure the dry-film thick- ness in accordance with Test Methods D6132, D4138, or D7091. Make corrections to the application, if necessary, by either applying more material if the dry film thickness is low (build-up coat) or applying another test patch if the dry film thickness is above the recommended maximum. N OTE 3—When using Test Method D6132 or Practice D7091, the dry film thickness is the difference in average thickness of the coating system less the average thickness of the in-place coating.

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