Journal of Adhesion Science and Technology, Vol.9, No.1, 81-95, 1995
EFFECTIVENESS OF WATER-BORNE PRIMERS FOR STRUCTURAL ADHESIVE BONDING OF ALUMINUM AND ALUMINUM-LITHIUM SURFACES
Three commercially available water-borne structural adhesive primers (two of which contain chromates) were evaluated for their effectiveness on both aluminum and aluminum-lithium alloy surfaces. The water-borne primers evaluated were American Cyanamid's BR 250 WBP and BR 250 WBP-NC, and 3M's EC 3982. The study control was 3M's EC 3924B, a solvent-borne epoxy primer. Studies included shear strength evaluations for each primer system using 3M's AF-163-2K film adhesive at 24-degrees-C and 104-degrees-C for both metals, at -55-degrees-C for aluminum-lithium, and at 93-degrees-C after 2 weeks exposure to a 93-degrees-C/condensing humidity environment for aluminum samples. Wedge crack extension tests were performed for samples exposed to 60-degrees-C and condensing humidity for 2 weeks. Floating roller peel studies were conducted on aluminum test samples only at -55, 24, and 104-degrees-C. A statistical analysis was performed to determine if the performance of the water-borne primers was as good as the performance of the solvent-borne primer. Statistical analyses of the data obtained indicated that only EC 3982 water-borne primer performed as well as the solvent-borne control when tested on aluminum-lithium. However, the water-borne primers performed as well as the solvent-borne primer when tested on aluminum in all cases except lap shear testing at 93-degrees-C (which was preceded by sample conditioning at 93-degrees-C and condensing humidity).