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ASTM F21-14

ASTM F21-14

Standard Test Method for Hydrophobic Surface Films by the Atomizer Test

2020-04-28 /Historical
Superseeded by:
Significance and Use:

5.1 The atomizer test as described in this test method is rapid, nondestructive, and may be used for control and evaluation of processes for the removal of hydrophobic contaminants. The test may also be used for the detection and control of hydrophobic contaminants in processing environments. For this application, a surface free of hydrophobic films is exposed to the environment and subsequently tested.4

5.2 This test method is related to Test Method F22. This test method may be suitable as an alternative to the water-break test when the surface of interest should not or cannot be immersed or doused with water, or when such immersion or dousing is impractical.

Note 1: This test method is not appropriate where line of sight evaluation is not feasible; or for assembled hardware where there is a risk for entrapment of water in faying surfaces or complex structures where it may not be effectively removed.

5.3 This test method is not quantitative and is typically restricted to applications where a go/no go evaluation of cleanliness will suffice.

5.4 For quantitative measurement of surface wetting, test methods that measure contact angle of a sessile drop of water or other test liquid may be used in some applications. Measurement methods based on contact angle are shown in Test Methods C813, D5946, and D7490; and Practice D7334.

5.4.1 Devices for in situ measurement of contact angle are available. These devices are limited to a small measurement surface area and may not reflect the cleanliness condition of a larger surface. For larger surface areas, localized contact angle measurement, or other quantitative inspection, combined with water break testing may be useful.

5.5 This test method is only for use on test surfaces composed of materials, such as metal surfaces, that are hydrophilic (“wettable”) when clean. Some materials such as gold and many plastics are poorly wetted by water, making contamination difficult to detect by this method.


1.1 This test method covers the detection of the presence of hydrophobic (nonwetting) films on surfaces and the presence of hydrophobic organic materials in processing environments. When properly conducted, the test will enable detection of fractional molecular layers of hydrophobic organic contaminants. On very rough or porous surfaces the sensitivity of the test may be significantly decreased.

1.2 The values stated in SI units are to be regarded as the standard. The inch-pound 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 appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

hydrophilic films; organic contamination; surface contamination; water-break;
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