Polymer Adhesion on Aluminum 2024-T3

Two surface coatings over aluminum untreated and with four pretreatments were used to develop characterization methods to quantify differences and similarities between thin film adhesion in the various combinations.  Aluminium 2024-T3 was pretreated by several standard methods: 1) Henkel’s proprietary chromate conversion coating, 2) Alodine 5200, 3) Pantheon’s proprietary non-chrome Prekote solution and 4) Silquest A 187 (γ-glycidoxypropyltrimethoxysilane). The pretreatments were compared to untreated Aluminium 2024-T3 surface coated with two polymer coatings;  a two component epoxy-polyamide primer (Deft 02GN083), and a one component thermoplastic DGEBA based polyepoxide   (Eponol 53-BH-35).  The surface properties of the pretreated aluminum panels were characterized by SEM-EDX, ATR and contact angle measurements to determine surface morphology, functional groups and acid-base properties.  The adhesion characteristics for the thin films, were related to the onset of gel formation at the coating/surface interface as characterized by chemorheology, DSC and TGA.  AFM was used to quantify the force-distance curves of the coatings at the molecular level over pretreated and non-pretreated aluminum in both the wet and glassy but pre-aged states.  The adhesion characterization was evaluated by pull-off adhesion, cross hatch and optical microscopy of the delaminating coatings and observed at various times related to aging intervals, with and without immersion in an aprotic solvent, N-methyl pyrrolidone.