Attachment and permanence of polyaniline coatings on stainless steel submerged in saline fluids

Stainless steel (SS) thin plates were covered with polyaniline (PANI) with consecutive electric glow discharges in H2O2 and in aniline vapors to sensitize the SS surface and to polymerize aniline on the plates. The objective was to form smooth polymeric coatings attached to the metallic surface that resist saline fluids for several months. The coated samples were submerged during 2 months in static and dynamic Phosphate-Buffered Saline solutions with pH = 7.4 at 37 degrees C to partially simulate the chemical conditions of an implant in the circulatory system. The results indicated that in the static fluid, the PANI coating remained adhered to the SS surface with some slight cracks. In the dynamic fluids, 4.6 mL/s, the coatings showed partial detachment of the superficial layers; however, the interior layers remained attached. In both cases, the contact angles on the coating were in the limit between hydrophilic and hydrophobic surfaces. The chemical analysis suggested the formation of O bridges that could contribute to the chemical adhesion of PANI on the SS surface. In general, the results indicated a good potential to retain the polymeric coating on SS under long immersion in saline fluids.