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 - 10 of 27
PublicationHard Anodizing and Plasma Electrolytic Oxidation of an Additively Manufactured Al-Si alloy(Elsevier Science, 2021-05-26) Mora Sánchez, H.; Olmo, Rubén del; Rams, J.; Torres, B.; Mohedano Sánchez, Marta; Matykina, E.; Arrabal Durán, RaúlPlasma Electrolytic Oxidation (PEO) and Hard Anodizing (HA) coatings are investigated on an Additively Manufactured (AM) Al10Si1Mg alloy obtained via Direct Metal Laser Sintering (DMLS). Results are compared to those obtained for a conventional A361 cast alloy. Findings revealed that the microstructure of the AM alloy, consisting of α-Al cells enclosed in a Si network, produces coatings that are more uniform –in terms of morphology, thickness and roughness of the coating/substrate interface– than those obtained on the cast alloy. However, enhanced oxidation of the fine Si network in the AM alloy results in softer coatings. In both alloys, PEO coatings demonstrate superior wear protection than HA due to the presence of mullite in the former. The anisotropy in the microstructure of the AM alloy influences the tribological behaviour of studied coatings, with the XZ plane showing superior wear performance. 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. PublicationEffect of cerium (IV) on thin sulfuric acid anodizing of 2024-T3 alloy(Elsevier Science BV, 2021-10-07) Olmo, R. del; Mohedano Sánchez, Marta; Visser, P.; Rodríguez Rodríguez, Araceli; Matykina, E.; Arrabal Durán, RaúlChromic acid anodizing (CAA) is still being used today for corrosion protection of fatigue-critical components in the aeronautic industry due to the lack of feasible alternatives. Ce-containing sulfuric acid anodizing (SAA) has been identified as a promising strategy for the development of alternatives to toxic CAA. This work explores thin sulfuric acid anodizing (TSAA) focusing on the following effects: (i) current density and voltage values; (ii) concentration of Ce(IV). Screening of the optimum combination in search of minimum thickness and the best corrosion resistance was performed using electrochemical impedance spectroscopy (EIS). Two Ce-containing anodic films were selected and further investigated in comparison with the inhibitor-free film in terms of morphology (FEG-SEM, TEM), composition (RBS), corrosion resistance (EIS, NSST), high-cycle fatigue and paint adhesion. The results indicate that the path to approach the CAA performance lies through thin (<1 μm) SAA-Ce films formed at low current density. PublicationDesign and Multidimensional Screening of Flash-PEO Coatings for Mg in Comparison to Commercial Chromium(VI) Conversion Coating(MDPI, 2021-02-17) Wierzbicka, Ewa; Mohedano Sánchez, Marta; Matykina, Endzhe; Arrabal Durán, RaúlREACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) regulations demand for an expedient discovery of a Cr(VI)-free alternative corrosion protection for light alloys even though the green alternatives might never be as cheap as current harmful technologies. In the present work, flash- plasma electrolytic oxidation coatings (FPEO) with the process duration < 90 s are developed on AZ31B alloy in varied mixtures of silicate-, phosphate-, aluminate-, and fluoride-based alkaline electrolytes implementing current density and voltage limits. The overall evaluation of the coatings’ anticorrosion performance (electrochemical impedance spectroscopy (EIS), neutral salt spray test (NSST), paintability) shows that from nine optimized FPEO recipes, two (based on phosphate, fluoride, and aluminate or silicate mixtures) are found to be an adequate substitute for commercially used Cr(VI)-based conversion coating (CCC). The FPEO coatings with the best corrosion resistance consume a very low amount of energy (~1 kW h m−2 µm−1). It is also found that the lower the energy consumption of the FPEO process, the better the corrosion resistance of the resultant coating. The superb corrosion protection and a solid environmentally friendly outlook of PEO-based corrosion protection technology may facilitate the economic justification for industrial end-users of the current-consuming process as a replacement of the electroless CCC process. PublicationCalcium Doped Flash-PEO Coatings for Corrosion Protection of Mg Alloy(MDPI, 2020-07-09) Wierzbicka, Ewa; Pillado Rios, Borja; Mohedano Sánchez, Marta; Arrabal Durán, Raúl; Matykina, EndzheThis study demonstrates a significant improvement of the corrosion resistance of an AZ31B magnesium alloy achieved by the application of 1 um-thin coatings generated by an environmentally friendly flash plasma electrolytic oxidation (FPEO) process in Ca-containing electrolytes. Two compounds with different solubility, calcium oxide (CaO) or calcium glycerophosphate (CaGlyP), were used as sources of Ca in the electrolyte. Very short durations (20–45 s) of the FPEO process were employed with the aim of limiting the energy consumption. The corrosion performance of the developed coatings was compared with that of a commercial conversion coating (CC) of similar thickness. The viability of the coatings in a full system protection approach, consisting of FPEO combined with an inhibitor-free epoxy primer, was verified in neutral salt spray and paint adhesion tests. The superior corrosion performance of the FPEO_CaGlyP coating, both as a stand-alone coating and as a full system, was attributed to the formation of a greater complexity of Ca2+ bonds with SiO2 and PO4 3- species within the MgO ceramic network during the in situ incorporation of Ca into the coating from a double chelated electrolyte and the resultant difficulties with the hydrolysis of such a network. The deterioration of the FPEO_CaGlyP coating during immersion was found over ten times slower compared with Ca-free flash-PEO coating. PublicationCorrosion of Steel Rebars in Anoxic Environments. Part II: Pit Growth Rate and Mechanical Strength(MDPI AG, 2021) García, Elena; Torres, Julio; Rebolledo, Nuria; Arrabal Durán, Raúl; Sánchez, JavierReinforced concrete may corrode in anoxic environments such as offshore structures. Under such conditions the reinforcement fails to passivate completely, irrespective of chloride content, and the corrosion taking place locally induces the growth of discrete pits. This study characterised such pits and simulated their growth from experimentally determined electrochemical parameters. Pit morphology was assessed with an optical profilometer. A finite element model was developed to simulate pit growth based on electrochemical parameters for different cathode areas. The model was able to predict long-term pit growth by deformed geometry set up. Simulations showed that pit growth-related corrosion tends to maximise as cathode area declines, which lower the pitting factor. The mechanical strength developed by the passive and prestressed rebar throughout its service life was also estimated. Passive rebar strength may drop by nearly 20% over 100 years, whilst in the presence of cracking from the base of the pit steel strength may decline by over 40%. PublicationEnergy consumption, wear and corrosion of PEO coatings on preanodized Al alloy: the influence of current and frequency(MPDI, 2022-10-13) Mohedano Sánchez, Marta; López, E.; Mingo Román, Beatriz; Moon, S.; Matykina, Endzhe; Arrabal Durán, RaúlThe influence of current and frequency on energy consumption of plasma electrolytic oxidation (PEO) of a commercial aluminium alloy pre-treated by conventional anodizing in sulphuric acid has been investigated. The combination of a 20-μm thick precursor anodic porous film, high current (500 mA cm−2) and frequency (400 Hz) during PEO enables up to 76% energy savings compared to direct PEO treatment (50 Hz). The time needed to achieve a uniform coating thickness was also reduced from 3350 s to 750 s, for PEO_50 and A + PEO_400, respectively. The wear and corrosion performance of the optimised coatings (400 Hz) were also improved despite the lower thickness of the coatings. Such improvement was mainly attributed to the microstructural refinement associated with high frequency processing and early transaction to the “soft-sparking” regime. The modification of the frequency has a stronger influence on the corrosion response than the presence of the anodic precursor. The best corrosion response was obtained for PEO_400 followed closely by A + PEO_400. PublicationCatálogo de actividades prácticas sobre corrosión y protección de materiales metálicos para el aprendizaje autónomoArrabal Durán, Raúl; Matykina, Endzhe; Mohedano Sánchez, Marta; Pardo Gutiérrez del Cid, Ángel; Muñoz Sánchez, Jesús Ángel; Gómez de Castro, Consuelo; Mora Sánchez, Hugo; Samaniego Miracle, Alejandro; Mateo Gómez, Gerardo; Pillado Ríos, Borja; Moreno Turiégano, Lara; Olmo Martínez, Rubén del; López Martínez, Esther; Carnero García, Jonás; Ramos Capón, CarolinaEl fin último del presente proyecto de innovación es la creación de recursos didácticos que permitan a los estudiantes desarrollar en casa y con elementos asequibles una serie de actividades prácticas dirigidas al aprendizaje autónomo sobre fundamentos de la corrosión y protección de materiales metálicos. PublicationOptimización de la resistencia a la corrosión y oxidación de materiales compuestos A3xx.x-SiCp mediante tratamientos de modificación superficial con sales lantánidas(Universidad Complutense de Madrid, Servicio de Publicaciones, 2007) Arrabal Durán, Raúl; Pardo Gutiérrez del Cid, Ángel; Merino Casals, María ConcepciónLos materiales compuestos de matriz metálica son objeto de investigación científica y aplicada desde hace dos décadas, aunque ha sido en los últimos años cuando verdaderamente se han convertido en buenos candidatos para aplicaciones en la industria aerospacial, automovilística, electrónica y de recreo. Las aleaciones de aluminio de moldeo reforzadas con partículas de carburo de silicio (SiCp) poseen un alto potencial para aplicaciones estructurales, debido a su excelente combinación de elevada resistencia y baja densidad. Sin embargo, es bien sabido que la resistencia a la corrosión y a la oxidación de los materiales compuestos de aluminio es inferior a la de las correspondieentes aleaciones sin refuerzo. Existen pocos estudios relativos a la protección contra la corrosión de los MCMM, aunque la tendencia es emplear el mismo tipo de recubrimientos o sistemas de proteccion que los designados para las aleaciones de aluminio. Los cromatos se han venido usando ampliamente en pretratamientos anticorrosivos para las aleaciones de aluminio, sin embargo, debido a la toxicidad del Cr6+, se han comenzado a buscar alternativas ecológicas. Una de las opciones más estudiadas ha sido el uso de elementos lantanidos, debido a su capacidad para formar hidróxidos insolubles y a su baja toxicidad. El objetivo del presente trabajo ha sido encontrar las condiciones óptimas de tratamientos superficiales anticorrosivos con sales lantanidas sobre materiales compuestos A3xx.x/SiCp.