Purpose:

State-of-the-art metal surface preparations for adhesive bonding consist primarily of anodizing or etching processes using strong acids or bases that rely on mechanical interactions for improved adhesion. These processes typically utilize hexavalent chromium and generate contaminated wastewater during rinsing. The surface preparations are followed by application of a chromated bond primer that can also contain high levels of volatile organic compounds (VOCs). Specific waterborne sol-gel chemistry, now commercially available, was developed during SERDP Project WP-130 Non-Chemical Surface Preparation. No-rinse processes utilizing sol-gel formulations were developed and optimized in the laboratory, demonstrating excellent adhesion via chemical bonding. The purpose of this project is to validate and demonstrate these high-performance sol-gel surface preparations that are environmentally friendly as well as simple and inexpensive to perform.

Description:

This project addresses surface preparation for adhesive bonding of aluminum, titanium, and steel substrates. The emphasis will be on defining tolerances for the steps involved in sol-gel processing under real-world constraints so that the procedures will be robust for implementation in a variety of applications. Processes using simple abrasion techniques, grit-blast pretreatment, and those used in conjunction with and without waterborne primer will be included in this demonstration. Demonstrations of several sol-gel processes will be conducted for Air Force, Navy, and Army depot- and field-level applications. The processes will be transitioned by refining the processing steps as necessary, generating data required by end-users to show that the processes are robust for implementation, and documenting procedures and savings.

Benefits:

The successful completion of this project will reduce the use of strong acids and bases, hexavalent chromium, and VOCs for Department of Defense bonded repair and original equipment manufacture. Because the sol-gel processes are quicker and simpler than existing approaches, maintenance costs and aircraft downtime will be reduced. Further savings in cost and time will be realized with a reduction in rework. Long-term moisture durability also will be significantly improved over current practices. (Anticipated Project Completion - 2007)

Contact:

Mr. James Mazza
Air Force Research Laboratory
Materials and Manufacturing Directorate
AFRL/MLSA, Building 652, Room 122
2179 12th Street
Wright-Patterson AFB, OH 45433-7718
Telephone: (937) 255-7778
Fax: (937) 656-4419
E-mail: james.mazza@wpafb.af.mil