Session 1: Aerospace/Defense Response to REACh
This talk focuses on development of the next generation of sol-gel pretreatments, i.e. sol-gel pretreatments with added corrosion protection for aerospace Al alloys.
Advances in Surface Finishing Technology
Corrosion protection of aerospace alloys has traditionally relied on the use of hexavalent chromium conversion coatings (CCC). However hexavalent chromium is a carcinogen and is toxic to the environment. Elimination of hexavalent chromium from conversion coatings, primers and processes will enable worker safety, enable cost avoidance by eliminating use of hazardous chemicals, baths and wastes and allow Boeing to be REACH, OSHA and EPA regulation compliant.
Boegel is an organo-silane based adhesion promoter qualified to BMS10-128 and primarily used on clad aluminum skins of the 737, 747, 767 and 777 aircrafts. The use of Boegel on these platforms eliminated the use of chromate conversion coatings on the exterior surface of the aircrafts and helped solve the rivet rash problems caused by poor paint adhesion to aluminum rivets.
Boegel EPII (commercially available as AC131 from 3M) was originally designed to enhance bond adhesion to aluminum surfaces and adhesion to subsequent epoxy primers, however provided no sacrificial standalone corrosion resistance to the base substrate. This study details investigating the addition of corrosion inhibitors to Boegel (corrosion resistant Boegel or CRB) to provide an extra layer of corrosion protection adjacent to the metal surface without compromising paint adhesion. Corrosion resistance of CRB was evaluated with best performing non-chromate primers from PPG, Akzo Nobel, Hentzen and Av-Dec and a PPG polyurethane topcoat. The corrosion performance of CRB was also compared to standard sol-gel (AC-131 from 3M), Alodine 1200, Alodine 5200 and SurTec 650V pre-treatments.