Evaluation of Cerium conversion Coating Parameters on Strength and Adhesion Properties of Optimized Epoxy Adhesives containing Butadiene Elastomers and Graphene Oxide Particles

The low strength of epoxy adhesives as well as their non-adhesion to aluminum surfaces have posed a serious challenge to the use of this resin in some special applications, including the aerospace industry. In order to improve tensile strength, two types of rubber acrylonitrile butadiene styrene (ABS) and methacrylate butadiene styrene (MBS) rubber modifiers were used. In order to better adherence of epoxy composites to the aluminum alloy AA2024-T3, the cerium conversion coating was used in optimal conditions. The results of electrochemical impedance spectroscopy and polarization curve showed that the obtained cerium conversion coating at 20 g / l cerium nitrate concentration, pH of 3.5, and 15 min of immersion time, has provided a uniform coating on the surface with the highest corrosion resistance and adhesion properties. Besides, the images of field emission scanning electron microscopy showed the formation of uniform cerium conversion coatings on the sample surface. The results of the stress-strain experiment showed that the addition of 4% of ABS and 1% of GO increased the tensile strength of up to 70% and 47%, respectively. Using conversion coatings resulted in a 60% increase of adhesion properties in the lap shear test. The pull-off test also proved a significant rise in adhesion strength due to the presence of conversion coatings.