Alginate (ALG) is a natural polymer used in a wide range of applications. Cerium is a sustainable corrosion inhibitor for many metal substrates. In this study, ALG/Ce3+ hydrogel microparticles are presented as an innovative cerium(III) reservoir system for the smart release of cerium ions. The active corrosion inhibition capacity of the ALG/Ce3+ complex was investigated. Tests using ALG/Ce3+ macrogels (beads) and electrochemical experiments showed that, in saline media, ALG/Ce3+ hydrogel was able to release Ce3+, which was subsequently exchanged with Al3+, Fe2+ and Fe3+ and, thus slowing the corrosion process of AA2024 (aluminum alloy) and AISI1020 (carbon steel) substrates, respectively. It is suggested that the presence of metal ions originated from the corrosion process triggers the cerium release. The corrosion protection of ALG/Ce3+ of the aluminum alloy was confirmed by polarization curves, electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET) and the protection of the carbon steel was demonstrated by EIS experiments. To the best of our knowledge, this is the first time that an alginate-based complex has been reported as an ion exchange corrosion-inhibiting system for metal substrates.

The tinplate, used in the packaging sector and formed from a metal substrate, comprises a steel base which has undergone a surface treatment to produce a thin layer of FeSn2, a tin layer and an oxide tin layer. Currently, packaging using surface treatment is based on the use of chromates because these metals provide an excellent corrosion resistance. Nontoxic alternatives to pre-treatments have been developed in recent years to replace the chromate process. The aim of this work is to analyze the performance of a new hybrid organic-inorganic film obtained from sol-gel consisting of the alkoxide precursors 3-(Trimethoxysilylpropyl)methacrylate (TMSM) and tetraethoxysilane (TEOS) with the addition of cerium nitrate with the scanning vibrating electrode technique (SVET), and electrochemical and morphological characterizations. Moreover, the evolution of the corrosion of the substrate was evaluated to propose a mechanism of corrosion. The results showed a galvanic coupling between the Sn/SnO2 coat (cathode) and the defects exposed at the ferrous base (anode). The organic-inorganic hybrid film containing a cathodic corrosion inhibitor was able to retard the corrosion of the tinplate.