Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Figure 1: Contact angle determination on a solid surface according to Young.12 Figure 3: Wetting of an acid-activated copper surface by water after treatment with Betatec gold post-dip, = 76°. Figure 2: Wetting of an acid-activated copper surface by water measured and recorded with a tensiometer. Figure 4: Wetting of an acid-activated nickel surface by water after treatment with Betatec gold post-dip, = 92°. often used as post-dips because they improve lubrication and abrasion proper- ties while simultaneously avoiding fretting corrosion. Nonetheless, because most lubricants, chemically speaking, are insulators a negative influence on the surface contact properties is observed. This article will describe such an aqueous post-dip treatment, providing cor- rosion resistance for various types of metal surfaces without impairing the con- tact resistance and other technical properties, while free from toxic or haz- ardous substances that may cause harm to the environment and living organisms. BETATEC*: POST-DIP TO IMPROVE CORROSION RESISTANCE The innovative Betatec aqueous gold post-dip requires a treatment time of only a few seconds after applying the gold deposit. Table 1 summarizes the process parameters. Properties of the post-dip include: • Imparting hydrophobic (water repelling) surface behavior • Repelling the action of corrosive vapor • Improved corrosion resistance. CONTACT ANGLE MEASUREMENT Contact angle measurements were carried out for wetted gold surfaces, before and after treatment, to determine the hydrophobic properties of Betatec post-dip. Measurements were carried out using a contact angle measuring device (ten- siometer). A mean of 30 individual measurements was used to minimize errors. The wetting of a solid surface with a liquid depends on the respective surface 148

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