Evaluation of novel multifunctional polymeric Schiff bases as anticorrosive agents for the medical grade 316L stainless steel.

In the field of biomaterials, the 316L stainless steel (316L SS) alloy is utilized in several countries as a temporary biomaterial without any prior treatment. In this work, corrosion protection and biocompatibility enhancements of the 316L SS alloy were performed. The influence of recently synthesized novel antibacterial, antimicrobial, and antioxidant polymeric materials, as corrosion inhibitors, on the 316L stainless steel surface was investigated. Initially, the primary amino groups of casein were reacted with the active carbonyl group of cinnamaldehyde to yield casein-cinnamadehyde (Ca-Cin) Schiff bases. These Schiff bases were then allowed to interact with the 316L SS alloy, resulting in self-assembled monolayers (SAMs) covering its surface. The features of these SAMs were then evaluated under simulated body fluid (SBF) conditions by electrochemical methods. Results confirmed the formation of SAMs from the studied Schiff bases, serving as mixed-type inhibitors on the 316L SS surface via a charge transfer mechanism. Moreover, these materials displayed both concentration- and immersion time-dependent corrosion inhibition efficiency, which exceeded 90% at 1000 ppm for Ca-Cin6 after 120 minutes of immersion in its solution. The corrosion inhibition efficiencies of these Schiff bases were optimized by investigating their dependence on the studied variables. The calculated thermodynamic parameters pointed out spontaneous adsorption of the Schiff base molecules on the metallic surface, obeying the Langmuir adsorption isotherm. These results reinforce that the materials under investigation exhibit promising features for refining the 316L stainless steel surface for implant applications.