Screwing Problems Solved
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Assembling screw connection elements and fasteners with chromium(VI)-free surfaces against electrocoated surfaces or aluminium parts has often caused fastening problems in the past, especially in particularly difficult applications. These problems have now been convincingly solved by an optimised silica-based seal with an integrated lubricant.
The implementation of EU Directive 2000/53/EC („End-of-Life Vehicle Directive“) in 2007 prohibited the use of coatings containing chromium(VI) in the automotive industry. The conversion to chromium(VI)-free surfaces for screws initially resulted in screwing problems. This was not, however, due to the chromium(VI)-free basecoat itself, especially because proven zinc flake coatings without chromium(VI) have been available for decades (Delta-MKS-Systeme).
Instead, problems were caused by the new silica-based sealers with an integrated lubricant that replaced the previously used wax-based lubricants. The silica-based topcoats offered better corrosion...