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Titanium Surface Treatments for Adhesive Bonding
NAVAL AIR DEVELOPMENT CENTER WARMINSTER PA AIRCRAFT AND CREW SYSTEMS TECHNOLOGY DIRECTORATE
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The aircraft industry prepares titanium surfaces for adhesive bonding using various types of abrasive, etchant, chemical, and anodize treatments. A study was made to determine pretreatment effects on adhesive bond durability of titanium under severe environmental conditions of temperature, humidity, and stress. Replicate sets of Ti-6Al-4V titanium specimens were provided to aircraft manufacturers who prepared the sets using eleven different pretreatment processes. The manufacturers also bonded the specimens with the same four adhesive systems. Wedge specimens, bounded from 0.150-inch thick Ti-6Al-4V titanium were tested in a 140 F, 100 relative humidity atmosphere for a period of eight weeks. Chromic acid anodize, alkaline etch, chromate-fluoride and alkaline peroxide treatments resulted in substantially lower crack growth rates than phosphate-fluoride treatments. There was a slight difference in performance ranking of bonding pretreatments depending upon the adhesive system used.
APPROVED FOR PUBLIC RELEASE