Bonding properties between nitrile-butadiene rubber and aluminum alloy treated by anodizing methods

In this work, the bonding properties between the LD7 aluminum alloy anodized by sulfuric acid or phosphoric acid and nitrile-butadiene rubber (NBR) were investigated. The bonding properties between the anodized aluminum alloys and NBR were compared with those between aluminum alloys treated by burnishing or sandblasting and NBR. The results revealed that, in comparison with sulfuric acid anodized samples, samples anodized in phosphoric acid solutions showed higher 90° peel strength. Under the same conditions, an increase in the anodic film thickness in the studied range may improve the adhesion property between rubber and an aluminum alloy. In comparison with aluminum alloys treated by burnishing or sandblasting, the surface of the anodized aluminum alloy showed homogeneously dispersed pores, which resulted in better and homogeneous bonding properties. A vacuum-drying process on the anodized aluminum alloys after they were coated with adhesives facilitated penetration of the adhesive molecules into the pores on the oxide layer, which considerably improved the bonding properties. In addition, rubber macromoleeules could also penetrate the pores in the aluminum oxide layer, leading to a strong physical anchor-hold interaction after a long time of soaking and diffusion.