Cerium and aluminum molybdates as inhibitors of the aluminum AA1050 corrosion process in aqueous NaCl solutions

• Published in: Materials and corrosion 2024-01, Vol.75 (1), p.73-83
• Main Authors: Byrne, Christian E., Quesada Cangahuala, Nereida V., D'Alessandro, Oriana, Deyá, Cecilia
• Format: Article
• Language: English
• Subjects: Aluminum; aluminum molybdate; Cathodic polarization; Cerium; cerium molybdate; Corrosion inhibitors; Linear polarization; Molybdates; Sodium chloride
• ISSN: 0947-5117; 1521-4176
• DOI: 10.1002/maco.202313940

Cerium molybdate and aluminum molybdate were synthesized by precipitation at controlled pH. The inhibitory properties of these solids on the corrosion process of aluminum in near‐neutral aqueous NaCl solutions were studied. Potentiodynamic polarization curves showed that both molybdates act as mixed‐type inhibitors. This is due to molybdate anion acts as an anodic inhibitor, while the trivalent cations Ce(III) and Al(III) have an inhibitory effect on the cathodic reaction. Linear polarization tests demonstrated a large increase in polarization resistance when these solids are added, resulting in an inhibition efficiency of 97% in both cases. Scanning electron microscopy and X‐ray energy dispersive microanalysis of the exposed surfaces revealed the formation of compact protective films rich in Mo and with no detectable Cl levels. Ce2(MoO4)3 and Al2(MoO4)3, were tested for corrosion inhibition of Al. While MoO42− acts as an anodic inhibitor, generating a Mo‐rich passivating layer that hinders chloride‐induced attack, Ce(III) or Al(III) act as cathodic inhibitors, generating a layer of insoluble oxides and hydroxides in the cathodic active zones.