“One-step electrodeposition method to generate a phytic-stearic-cerium hydrophobic coating on AZ91D magnesium alloy

A. P. LOPERENA; I.L. LEHR

Buenos Aires

Congreso; 11th World Congress of Chemical Engineering (WCCE11); 2023

Asociación Argentina de Ingenieros Químicos

Biodegradable metallic materials have been extensively studied in recent years due to their use in substitution and generation of tissues. Among others, magnesium appears as a very promising biomaterial [1,2].In recent years, environmentally friendly and biocompatible coatings such as those based on lanthanides or organic acids such as phytic acid, stearic acid have been studied.On the other hand, superhydrophobic coating has been considered to be a promising alternative for different biomedical applications due to their properties such as protein adsorption control, antibacterial activity and self-cleaning [3]. In addition, the superhydrophobic surfaces can enhance corrosion resistance of metallic materials [4].The main objective of this work is to generate a unique hydrophobic coating on AZ91D Mg alloys that combines both the corrosion inhibition properties of the cerium based films and the ability to form stable chelates of phytic and stearic acid with Mg ions.Materials and methodsThe working electrodes were prepared from rods of AZ91D magnesium alloy with an exposed area of 0.070 cm2. The samples were treated in an electrolyte solution containing phytic acid (Phy) (10-50 mM), stearic acid (SA) (1-30 mM) and cerium nitrate hexahydrate (Ce(NO3)3) (1-10 mM) in a purified nitrogen gas saturated atmosphere. The temperature employed was 50 ºC. The optimal experimental conditions (solution composition, temperature, formation time and applied potential) were determined to allow obtaining a coating with superior anticorrosive performance. Electrochemical studies were performed using an Autolab/PGSTAT 128N potentiostat/galvanostat. The degree of protection achieved was evaluated in simulated physiological solution (Ringer's solution) by monitoring the open circuit potential, polarization techniques and faradaic impedance. Static CA of the coating surfaces with Ringer solution was measured to evaluate the hydrophilicity or hydrophobicity of the samples. .ResultsAn uniform, compact and adherent coating was obtained on AZ91D magnesium alloy in a solution containing Phy, SA and Ce(NO3)3 under potentiostatic conditions (RPhy-SA/Ce). From the CA results, it was demonstrated that the hydrophilic phytic-cerium-based coatings surfaces can be converted into hydrophobic surfaces by the addition of SA in the treatment solution. The CA measurements for all the evaluated coatings suggest that 30 mM SA is the optimal bath concentration to generate superhydrophobic surfaces. Electrochemical studies agreement with the CA results. The films obtained at - 0.50 V for 30 min in 30 mM Phy, 30 mM SA and 5 mM Ce(NO3)3 pH 2.9 at 50 ºC showed superior anticorrosive efficiency compared to RPhy, RSA and RCe films in Ringer's solutions.ConclusionsA superhydrophobic coating with a superior anticorrosive efficiency in simulated physiological solution was obtained in a solution containing phytic acid, stearic acid and cerium nitrate. The improvement in the corrosion resistance is associated with the ability of phytic acid and stearic acid to form stable chelates on the substrate surface combined with the presence of insoluble cerium oxide precipitates.References1. Ali, M., Hussein, M.A,. Al-Aqeeli, N. (2019). Magnesium-based composites and alloys for medical applications: A review of mechanical and corrosion properties. Journal of Alloys and Compounds 792,1162-1190.2. Dong, J., Lin, T., Shao, H,. Wang, H., Wang, X., Song, K,. et al. (2022). Advances in degradation behavior of biomedical magnesium alloys: A review. Journal of Alloys and Compounds 908,1-16.3. Kumar, R., Sahani, A.K.(2021). Role of superhydrophobic coatings in biomedical applications. Materials today: proccedings 45 (6) 5655-5659.4. Qu, J., Chen, X. (2019). Corrosion resistance of phytic acid / Ce (III) nanocomposite coating with superhydrophobicity on magnesium. Journal of Alloys and Compounds 787,145-151.