The water break test is a common way to test for surface cleanliness. It allows the user to test for the presence of hydrophobic contaminants, which can be detrimental to adhesion. It is usually considered non-destructive to the part because it uses only water.
How the Water Break Test is Performed
To perform a water break test in accordance with the ASTM-F22 Handbook, the material is dipped in water and withdrawn vertically. The behavior of that water on the surface reveals the surface energy which is determined by the cleanliness level. If the surface is clean it will show high surface energy and the water will spread out due to its attraction to the surface. This strongly correlates to adhesion ability.
Uses of the Water Break Test
Water break is mostly used on metals to expose the presence of contaminants or after surface processes such as etching, anodizing, painting, priming, coating, grit-blasting, or sanding. However, these tests can be messy and sometimes can result in unintended contaminating due to impure water. The user must also allot a significant amount of time for the part to dry after the test. These tests require a trained user who can determine a "go" or "no go" result. This leads to subjectivity. Lastly, the test can lack sensitivity as a surface can visually appear clean, when it's not.
Is There a Surface Cleanliness Measurement Instrument?
In contrast, the Surface Analyst™ is sensitive to the top 2-3 molecular layers of a surface. By using a single drop of highly purified water deposited on the surface you can accurately predict how successful adhesion will be with virtually no mess and no threat to the measurement surface. This is a contact angle measurement. Furthermore, the Surface Analyst is a small, handheld, user friendly instrument, that has the ability to measure on almost any surface or surface orientation, regardless of shape or roughness. The automatic calculation of contact angle removes operator subjectivity. The Surface Analyst measures on a cleanliness scale as opposed to a binary go/no go result. So measurements taken with the Surface Analyst can more closely map out a surface's characteristics.
Handpicked Related Surface Testing Content:
Resources to Learn About Surface Science
To find out more about an alternative to the water break test, download the "Manufacturer's Roadmap to Eliminating Adhesion Issues in Production" ebook. This guide gives clear insight into eliminating guesswork around adhesion so manufacturers can achieve consistent and successful results.