Abstract
The goal of this work was to compare the performance of our home-built dynamic sessile drop contact angle (CA) goniometer with our NIMA Dynamic Surface Tensiometer. Water CA measurements on different alloy samples (aluminium brass, copper-nickel 70/30, stainless steel 304) have been carried out by 1) sessile drop and 2) Wilhelmy plate method. Different sets of substrates were i) cleaned; ii) cleaned and pre-treated; iii) cleaned, pre-treated and coated with atactic polystyrene. During these experiments, the main features of the two setups in connection with our sample properties were understood. We therefore found it desirable and justified to sum up our findings.
Highlights
Contact angle (CA) measurement is perhaps the simplest routine measurement to give information about the success of a coating procedure
The original samples were sections of condenser tubes, and the curvature presented a problem in the objective evaluation of the measured CAs. (A mathematical correction derived for the curvature will be presented later elsewhere.) the samples were flattened in a press
The small arrows on the Figure indicate where the sample first came into contact with water surface during immersion, respectively the point where it detached from the water surface during withdrawal
Summary
Contact angle (CA) measurement is perhaps the simplest routine measurement to give information about the success of a coating procedure. The first method is direct, as the liquid droplet is placed on the surface to be characterized and the image is captured and the angle of contact formed at the gas/liquid/solid interfaces is evaluated. The method can be used in both static and dynamic mode. During this latter, the drop is continuously increased by adding liquid to it and the CA is measured in function of the drop volume. The highest possible angle measured is regarded as the advancing CA. The drop size is gradually decreased by withdrawing liquid from it, while the CA is again recorded in function of the volume. The lowest possible measured angle is taken as the receding CA
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