Person: Arrabal Durán, Raúl
Universidad Complutense de Madrid
Faculty / Institute
Ingeniería Química y de Materiales
Ciencia de los Materiales e Ingeniería Metalúrgica
Now showing 1 - 5 of 5
PublicationLDH Post-Treatment of Flash PEO Coatings(MDPI, 2019-05-30) Olmo, Rubén del; Mohedano Sánchez, Marta; Mingo, Beatriz; Arrabal Durán, Raúl; Matykina, EndzheThis work investigates environmentally friendly alternatives to toxic and carcinogenic Cr (VI)-based surface treatments for aluminium alloys. It is focused on multifunctional thin or flash plasma electrolytic oxidation (PEO)-layered double hydroxides (LDH) coatings. Three PEO coatings developed under a current-controlled mode based on aluminate, silicate and phosphate were selected from 31 processes (with different combinations of electrolytes, electrical conditions and time) according to corrosive behavior and energy consumption. In situ Zn-Al LDH was optimized in terms of chemical composition and exposure time on the bulk material, then applied to the selected PEO coatings. The structure, morphology and composition of PEO coatings with and without Zn-Al-LDH were characterized using XRD, SEM and EDS. Thicker and more porous PEO coatings revealed higher amounts of LDH flakes on their surfaces. The corrosive behavior of the coatings was studied by electrochemical impedance spectroscopy (EIS). The corrosion resistance was enhanced considerably after the PEO coatings formation in comparison with bulk material. Corrosion resistance was not affected after the LDH treatment, which can be considered as a first step in achieving active protection systems by posterior incorporation of green corrosion inhibitors. PublicationDegradation Behaviour of Mg0.6Ca and Mg0.6Ca2Ag Alloys with Bioactive Plasma Electrolytic Oxidation Coatings(MDPI, 2019-06-13) Moreno Turiegano, Lara; Mohedano Sánchez, Marta; Mingo, Beatriz; Arrabal Durán, Raúl; Matykina, EndzheBioactive Plasma Electrolytic Oxidation (PEO) coatings enriched in Ca, P and F were developed on Mg0.6Ca and Mg0.6Ca2Ag alloys with the aim to impede their fast degradation rate. Different characterization techniques (SEM, TEM, EDX, SKPFM, XRD) were used to analyze the surface characteristics and chemical composition of the bulk and/or coated materials. The corrosion behaviour was evaluated using hydrogen evolution measurements in Simulated Body Fluid (SBF) at 37 °C for up to 60 days of immersion. PEO-coated Mg0.6Ca showed a 2–3-fold improved corrosion resistance compared with the bulk alloy, which was more relevant to the initial 4 weeks of the degradation process. In the case of the Mg0.6Ag2Ag alloy, the obtained corrosion rates were very high for both non-coated and PEO-coated specimens, which would compromise their application as resorbable implants. The amount of F− ions released from PEO-coated Mg0.6Ca during 24 h of immersion in 0.9% NaCl was also measured due to the importance of F− in antibacterial processes, yielding 33.7 μg/cm2, which is well within the daily recommended limit of F− consumption. PublicationData: Energy consumption, wear and corrosion of PEO coatings on preanodized Al alloy: the influence of current and frequency. Journal of Materials Research and Technology, 21, pp. 2061-2075 (2022).Mohedano Sánchez, Marta; López Martínez, Esther; Mingo, Beatriz; Moon, Sungmo; Matykina, Endzhe; Arrabal Durán, Raúl; Pillado Rios, Borja PublicationLayered Double Hydroxide Coatings Loaded with Corrosion Inhibitors for Corrosion Protection of AZ31 †(MDPI, 2021) Pillado Rios, Borja; Mohedano Sánchez, Marta; Olmo Martínez, Rubén del; Mingo, Beatriz; Matykina, Endzhe; Arrabal Durán, RaúlLayered double hydroxide (LDHs) coatings were developed for the corrosion protection of AZ31 Mg alloy. AZ31 is widely used in the transport industry due to its low mass density and good mechanical properties. LDH coatings were fabricated under co-precipitation conditions and applied under hydrothermal conditions. Two different systems Zn-Al LDH and Li-Al LDH were studied. Specimens were post-treated via immersion for 2 h at 45 °C in inhibitor aqueous baths. Na2WO4·H2O and LiNO3 inorganic inhibitors were used, respectively, to produce inhibitor-loaded systems: Zn-Al LDH(W) and Li-Al LDH(Li). The characterization of the coatings was carried out by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The corrosion process was studied by electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET). The surface was also evaluated via the determination of water drop contact angle and the performance of a paint adhesion test using an epoxy primer. The characterization of the coating revealed two-layered coatings with a denser inner layer and a flaky outer layer. Both coatings improved the corrosion resistance of the AZ31 alloy. Loading with inhibitor further increased the corrosion resistance by one order of magnitude (bare substrate, Z10mHz~102 Ω cm2; LDH, Z10mHz~103–4 Ω cm2; LDH-inhibitor, Z10mHz~105 Ω cm2). PublicationEffects of pre-anodizing and phosphates on energy consumption and corrosion performance of PEO coatings on AA6082(Elsevier, 2021-01-22) Mohedano Sánchez, Marta; Mingo, Beatriz; Mora Sánchez, Hugo; Matykina, Endzhe; Arrabal Durán, RaúlA significant reduction in the energy consumption of Plasma Electrolytic Oxidation (PEO) coatings on AA6082 alloy was obtained using strategies based on electrolyte selection and a precursor anodic film. PEO coatings were developed on AA6082 in silicate-based electrolytes with different phosphate species without and with a precursor oxide layer. The electrical response and, therefore, the specific energy consumption depended on the phosphate species and most notably on the applied pretreatment. The best result was obtained after anodic pretreatment and PEO in silicate-polyphosphate electrolyte with a reduction up to ⁓66% in comparison with the most conventional treatment (direct PEO in orthophosphate electrolyte). The corrosion response is not affected significantly by the pre-anodizing treatment either for short or prolonged immersion times revealing that coatings synthesised under high-energy efficient conditions have comparable corrosion performance under aggressive corrosive environments compared to conventional PEO processes.