ASTM D1212-91(R2020) pdf free download

ASTM D1212-91(R2020) pdf free download.Standard Test Methods for Measurement of Wet Film Thickness of Organic Coatings
1. Scope
1.1 These test methods cover the determination of wet film thickness of organic coatings such as paint, varnish, and lacquer. Two methods are described as follows: 1.1.1 In Test Method A, the Wet Film Thickness Gage (English or Metric graduation (see 5.1)) is used to measure wet film thicknesses up to 60 mils on the English scale series, and up to 700 µm on the metric scale series (Sections 5 – 8). 1.1.2 In Test Method B, the Pfund Gage is used to measure wet film thicknesses up to 14.2 mils (360 µm) (Sections 9 – 13). 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.
3. Summary of Test Methods
3.1 The material is applied in the laboratory to plane, rigid test panels or in the field to the surface being coated. The wet film thickness is determined as quickly as possible to reduce shrinkage due to solvent loss. 3.2 In Test Method A, a gage with one eccentric and two concentric wheels is rolled over the surface and the point where the eccentric wheel first touches the wet film is determined. 3.3 In Test Method B, a gage with a convex lower surface is pushed into the wet film until the center touches the substrate. The diameter of the spot of wet coating left on the convex surface is measured and the film thickness calculated from the diameter of the spot and the radius of curvature.
4. Significance and Use
4.1 Wet film thickness measurements aid in the prediction of dry film thickness. In instances where dry film thickness cannot be measured nondestructively, wet film thickness is frequently specified. Also, the ability to determine wet film thickness during application can provide the opportunity to correct the application procedures.
5. Apparatus
5.1 Wet Film Thickness Gage—Two versions ofthe gage are now in use: 3 The original design as shown in Fig. 1 and a later design as shown in Fig. 2. Both designs consists ofan eccentric center wheel supported by two concentric wheels so as to provide two scales that are bilaterally symmetrical. As the gage is rolled on the film, there is a change in clearance between the wet film and the eccentric wheel. The point at which the film first touches the center wheel measures the thickness of the film. 5.2 The later design shown in Fig. 2, moves the eccentric wheel from between the concentric wheels, as shown in Fig. 1, to the outside of the gage and closer to one of the concentric wheels. Gage reading errors of parallax across the gage are eliminated as the two scales are placed directly on the eccentric wheel and errors when measuring on uneven support surfaces are reduced by placing the eccentric wheel closer to one of the supporting concentric wheels. 5.3 Best precision is obtained when using the near linear central portion of each scale, constituting about 80 % of its total range as shown in the diagram in Fig. 1 and Fig. 2. Therefore, the range of the particular gage selected for use should be such that the measured film thickness falls within, and preferably toward the center of the middle 80 % of each scale. Gages are available covering the following ranges in mils and microns