Metal Finishing Guide Book


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Figure 1: Contact angle determination on a solid surface according to Young.12 Figure 2: Wetting of an acid-activated copper surface by water measured and recorded with a tensiometer. Figure 3: Wetting of an acid-activated copper surface by water after treatment with Betatec gold post-dip, ��� = 76��. 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 properties 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 corrosion resistance for various types of metal surfaces without impairing the contact resistance and other technical properties, while free from toxic or hazardous 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 (tensiometer). 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 275

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