Person:
Mohedano Sánchez, Marta

First Name

Marta

Last Name

Mohedano Sánchez

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Químicas

Department

Ingeniería Química y de Materiales

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Now showing 1 - 10 of 25

Chromate-Free Corrosion Protection Strategies for Magnesium Alloys—A Review: PART I—Pre-Treatment and Conversion Coating
(MDPI AG, 2022) Vaghefinazari, Bahram; Wierzbicka, Ewa; Visser, Peter; Posner, Ralf; Arrabal Durán, Raúl; Matykina, Endzhe; Mohedano Sánchez, Marta; Blawert, Carsten; Zheludkevich, Mikhail; Lamaka, Sviatlana
Corrosion protection systems based on hexavalent chromium are traditionally perceived to be a panacea for many engineering metals including magnesium alloys. However, bans and strict application regulations attributed to environmental concerns and the carcinogenic nature of hexavalent chromium have driven a considerable amount of effort into developing safer and more environmentally friendly alternative techniques that provide the desired corrosion protection performance for magnesium and its alloys. Part I of this review series considers the various pre-treatment methods as the earliest step involved in the preparation of Mg surfaces for the purpose of further anti-corrosion treatments. The decisive effect of pre-treatment on the corrosion properties of both bare and coated magnesium is discussed. The second section of this review covers the fundamentals and performance of conventional and state-of-the-art conversion coating formulations including phosphate-based, rare-earth-based, vanadate, fluoride-based, and LDH. In addition, the advantages and challenges of each conversion coating formulation are discussed to accommodate the perspectives on their application and future development. Several auspicious corrosion protection performances have been reported as the outcome of extensive ongoing research dedicated to the development of conversion coatings, which can potentially replace hazardous chromium(VI)-based technologies in industries.
Hybrid functionalized coatings on Metallic Biomaterials for Tissue Engineering
(Elsevier, 2021-07-17) Santos Coquillat, Ana María; Martínez Campos, Enrique; Mora Sánchez, Hugo; Moreno Turiegano, Lara; Arrabal Durán, Raúl; Mohedano Sánchez, Marta; Gallardo, Alberto; Rodríguez Hernández, Juan; Matykina, Endzhe
The review encompasses state-of-the-art strategies for design and fabrication of smart biomaterials for tissue engineering. The focus of the work is mainly put on metallic biomaterials with hybrid coatings consisting of bioceramic and polymeric layers with hierarchical organization and drug-eluting capacity. Key technologies and steps to design hybrid smart and multifunctional coatings on metallic cores for bone regeneration implants and cardiovascular stents are outlined, including additive manufacturing of titanium and magnesium alloys for permanent and temporary implant applications. Three levels of hierarchical surface functionalization are described: i) in situ modification of the core material, incorporating bioactive inorganic species and phases by means of ceramic coatings via anodic electrochemical treatments; ii) post-treatment application of polymer layers, monolithic or with specific porous breath figure topography; and iii) application of a cellular therapy component (single cell or cell sheet). Recent progress in incorporation of drug-eluting functionality into such materials via direct or nanocarrier-assisted loading is also highlighted.
Effects 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, Raúl
A 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.
Ca-based sealing of plasma electrolytic oxidation coatings on AZ91 Mg alloy
(Elsevier, 2021-04-22) Lu, Xiaopeng; Ma, Jirui; Mohedano Sánchez, Marta; Pillado Rios, Borja; Arrabal Durán, Raúl; Qian, Kun; Li, Yan; Zhang, Tao; Wang, Fuhui
Plasma electrolytic oxidation (PEO) coatings on AZ91 Mg alloy were sealed in calcium nitrate solutions at different pH values (3, 4 and 5). Sodium dodecyl sulfate (SDS) was added to study the effect of SDS on the corrosion resistance of the sealed coatings. The microstructure, chemical composition and corrosion resistance of the coatings were investigated by means of SEM, XPS, XRD and electrochemical corrosion tests. The corrosion performance of the coatings was improved due to precipitation of Ca-containing precipitate. Low pH and SDS addition enhanced hydroxyapatite precipitation and produced hydrophobic coatings with worse paint adhesion but better corrosion resistance.
Permanganate loaded Ca-Al-LDH coating for active corrosion protection of 2024-T3 alloy
(Elsevier, 2022-02-01) Olmo Martínez, Rubén del; Mohedano Sánchez, Marta; Matykina, Endzhe; Arrabal Durán, Raúl
Ca-Al-Layered Double Hydroxide (Ca-Al-LDH) coating was explored on 2024-T3 aluminium alloy by in situ growth methodology following a 1 h treatment at atmospheric pressure. Mn-based species were successfully incorporated into the Ca-Al-LDH structure by a low-temperature post-treatment (Ca-Al-LDH-Mn). Both LDH coatings disclosed a flaky-like morphology and low thickness (~0.6 µm). Ca-Al-LDH-Mn coating showed optimal paint adhesion and the highest long-term corrosion resistance in 3.5 wt% NaCl solution. Evaluation of scribed LDH specimens by SEM/EDS techniques up to 7 days of immersion in 3.5 wt% NaCl solution revealed that the presence of Mn species in the Ca-Al-LDH-Mn provided active corrosion protection.
Hard 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, Raúl
Plasma 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.
Energy 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, Raúl
The 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.
LDH Post-Treatment of Flash PEO Coatings
(MDPI, 2019-05-30) Olmo, Rubén del; Mohedano Sánchez, Marta; Mingo, Beatriz; Arrabal Durán, Raúl; Matykina, Endzhe
This 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.
Data: 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
Effect 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, Raúl
Chromic 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.