Evaluation of the effect of sodium alginate, hydroxyethyl cellulose, aspartame, and poly(ethylene oxide)-b-poly(propylene oxide) copolymer on the in-vitro corrosion of AZ31 Mg alloy in simulated body fluid.

Abstract

Research on Mg-based implants has increased recently because of their compatibility and biodegradability. Despite this promise, challenges related to high corrosion rates hampered wide-scale deployment. This paper explores the inhibiting properties of biomacromolecules, sodium alginate (ALG), hydroxyethyl cellulose (HEC), aspartame (ASP), and poly(ethylene oxide)-b-poly(propylene oxide) copolymer (PEO-b-PPO) on AZ31 Mg alloy in simulated body fluid at 37 °C. Results revealed that PEO-b-PPO accelerated, ALG insignificantly inhibited, while ASP and HEC showed moderate inhibition. At 2000 ppm, ASP and HEC offered 54 % and 53 % protection after 48 h and over 65 % if blended. Mechanistic insights were gained via XPS, FTIR, and distribution of relaxation times (DRT) analysis. Three corrosion mechanisms, Cl^- transport, charge transfer, and ion transport across inherent MgO lattice are revealed by DRT and occurred at f = 5 Hz, f = 21 Hz and 832 Hz, and f = 100,000 Hz. Inhibitors' presence prolonged the relaxation time or changed the frequency of occurrence. Carbonates (Mg, Ca), hydroxides (Mg), and phosphates are the main corrosion products. Adsorbed ASP and HEC molecules are mixed with these products to protect the alloy. These findings offer a better understanding of the underlying mechanisms that could facilitate the development of target-oriented corrosion inhibitors for Mg.