ASTM D1186-01 pdf free download.Standard Test Methods for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to a Ferrous Base.
1.1 These test methods cover the nondestructive measurement of the dry film thickness of nonmagnetic coatings applied over a ferrous base material using commercially available test instruments. The test methods are intended to supplement manufacturers’ instructions for the manual operation of the gages and are not intended to replace them. They cover the use of instruments based on magnetic measuring principles only. Test Method A provides for the measurement of films using mechanical magnetic pull-off gages and Test Method B provides for the measurement of films using magnetic electronic gages.
1.2 These test methods are not applicable to coatings that will be readily deformahie under the load of the measuring instruments, as the instrument probe must be placed directly on the coating surface to take a reading.
1.3 The values given in SI units of measurement are to he regarded as the standard. The values in parentheses are for intbrmation only.
3. Summary of Test Method
3. 1 Instruments complying with this test method measure thickness by using a spring calibrated to determine the force required to pull a magnet from a ferrous base coated with a nonmagnctic film. The instrument must be placed directly on the coating surface to take a reading.
3.2 The attractive force of the magnet to the substrate varies inversely with the thickness of the applied film. The spring tension required to overcome the attraction of the magnet to the substrate is shown on the instrument scale as the distance (in mils or microns) between the magnet and the substrate.
4. Significance and Use
4.1 Many coating properties are markedly affected by the thickness of the dry film such as adhesion, corn)sion protection, flexibility, and hardness. To be able to compare results obtained by different operators, it is essential to know film thick ness.
4.2 Most protective and high performance coatings are applied to meet a requirement or a specification for the dry-film thickness of each coat, or for the complete system. or both. Coatings must be applied within certain minimum and maximum thicknesses to fill their expected function. In addition to potential performance deficiencies, it is uneconomical to apply more material than necessary when coating large areas. This test method is used to measure film thickness of coatings on ferrous metals.
5. Apparatus
5. 1 Permanent Magnet, small, either attached directly to a coil spring (“pencil” gage) or to a horizontal lever arm that is attached to a helical spring (“dial-type” gage). Increasing force is applied to the magnet by extending the coil spring in the first case or turning a graduated dial that coils the helical spring in the second. The readings obtained are shown directly on the instrument scale.
5.2 coating Thickness Standards, with assigned values traceable to national standards are available from several sources, including most manufacturers of coating thickness gages.ASTM D1186 pdf download.