Sol-Gel Technology for Low-VOC, Nonchromated Adhesive Bonding Applications SERDP; Project PP-1113, Task 1

摘要

A government-industry team, primarily funded by the Strategic Environmental Research and Development Program (SERDP) under Project PP-1113, developed new environmentally friendly metal surface preparations for adhesive bonding applications. These processes were based on waterborne, nonchromated chemistry developed by Boeing and designated Boegel-EPII. Preparation of aluminum, titanium, and stainless steel adherends was investigated for on- component repair as well as original equipment manufacturer (OEM) applications. The bulk of the work was conducted to establish pretreatment steps for cleaning, deoxidizing, and roughening metal surfaces. Multiple viable approaches, varying in degree of effectiveness and complexity, were developed. Sol-gel chemistry application processes were also investigated as were post-treatment priming operations. Surface characterization efforts and kitting studies for the multicomponent sol-gel chemistry received significant attention. Performance of surface preparations was primarily evaluated by means of the wedge test, although many additional tests were conducted, on several epoxy-based film and paste adhesives. The best processes developed, utilizing alumina grit-blasting pretreatment, are quite robust and yielded excellent bond strength and moisture durability results, rivaling the best existing practices. Variations using nongrit-blast approaches outperformed many approved repair processes. Government and industry organizations have begun to implement the new sol-gel processes for aluminum, titanium, and steel adhesive bonding applications.