Hydrophobic Surface Films
ASTM International Committee E21 on Space Simulation and Applications of Space Technology is requesting input on upcoming revisions for two standards under the jurisdiction of Subcommittee E21.05 on Contamination.
The two standards to be revised are F21, Test Method for Hydrophobic Surface Films by the Atomizer Test, and F22, Test Method for Hydrophobic Surface Films by the Water-Break Test. Commonly known as water-break tests, the two standards are used to evaluate surface cleanliness by observing surface wetting by water.
“Observation of the behavior of water after application by atomizer, as in F21, or on removal of the part from immersion, as in F22, has been used for decades, if not centuries, to assess surface cleanliness,” says Nikki Lowrey, senior contamination control engineer, Jacobs Technology Inc. “These test methods, while not quantitative, are frequently used as rapid, low-cost methods to verify that surfaces are sufficiently free of hydrophobic contaminants to proceed to application of primer, plating, adhesives, conversion coatings or other surface treatments.”
All interested parties are invited to participate in E21.05’s work. In order to proceed with revisions to F21 and F22, E21.05 would like feedback on current industry practices in water-break testing, particularly in the following areas:
- Purity requirements for the test water;
- Low-cost alternatives to the cleaved mica blank method for verification of the absence of hydrophilic contaminants in the test materials that may invalidate the test;
- Addition of a section discussing the relationship of F21 and F22 to surface energy and the quantitative measurement of cleanliness by contact angle, comparative test solutions (such as in D2578, Test Method for Wetting Tension of Polyethylene and Polypropylene Films, or other methods);
- Consideration for an addition to F22 on the application of this method to testing on large parts where water break is observed after flowing water over the surface from a nozzle.
- Addition of notes on the proper use and misuse of water-break testing, including proper drying after the test to prevent recontamination.
CONTACT ASTM Staff: Rick Lake • Phone: 610-832-9689 | Upcoming Meeting: April 19 • April Committee Week • Phoenix, Ariz.
This article appears in the issue of Standardization News.