Open Access
Multifunctional protective PVC-ZnO nanocomposite coatings deposited on aluminum alloys by electrospinning
(MDPI, 2019) Iribarren Zabalegui, Álvaro; Rivero Fuente, Pedro J.; Berlanga Labari, Carlos; Larumbe Abuin, Silvia; Miguel, Adrián; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, PRO-UPNA 18 (6107)
This paper reports the use of the electrospinning technique for the synthesis of nanocomposite micro/nanofibers by combining a polymeric precursor with hydrophobic behavior like polyvinyl chloride (PVC) with nanoparticles of a corrosion inhibitor like ZnO. These electrospun fibers were deposited on substrates of the aluminum alloy 6061T6 until forming a coating around 100 m. The effect of varying the different electrospinning deposition parameters (mostly applied voltage and flow-rate) was exhaustively analyzed in order to optimize the coating properties. Several microscopy and analysis techniques have been employed, including optical microscopy (OM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Water contact angle (WCA) measurements have been carried out in order to corroborate the coating hydrophobicity. Finally, their corrosion behavior has been evaluated by electrochemical tests (Tafel curves and pitting potential measurements), showing a relevant improvement in the resultant corrosion resistance of the coated aluminum alloys.
Open Access
Characterization of two iron bullets from the royal ammunition factory of Eugi (Spain)
(Technical Faculty, University of Belgrade, 2018) Zalakain Iriazabal, Iñaki; Berlanga Labari, Carlos; Álvarez Vega, Lucas; Rivero Fuente, Pedro J.; Valencia Monreal, Javier; Rodríguez Trías, Rafael; Mekanika, Energetika eta Materialen Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Mecánica, Energética y de Materiales
In this work, a comparative analysis of two iron bullets found in The Royal Ammunition Factory of Eugi in Navarra (Spain) was performed. Both bullets presented a spherical shape with a relatively good state of preservation, belonging to the last years of the factory production (1766-1850). Several techniques such as microhardness, X-ray fluorescence (XRF), light (LM) and scanning electron microscopy (SEM), optical mission spectroscopy (OES) and energy dispersive X-ray spectroscopy (EDX) analysis were used in order to identify the manufacturing process of the two bullets. The analyses of the microstructures carried out by LM and SEM showed that one bullet was composed of white cast iron with a pearlitic matrix, steadite and graphite; while the other was composed of grey cast iron with a pearlitic matrix, graphite and a low amount of steadite. The chemical analysis of the bullets carried out by OES indicated significant differences in the amount of silicon and phosphorous. The variation in silicon content could suggest that the foundry temperature under oxidizing environment varied during the casting. The SEM and EDX analyses showed both bullets had manganese sulphide inclusions but only one of the bullets exhibited titanium and vanadium inclusions. The microhardness analyses carried out revealed Vickers hardness differences along the diameter. This variation could be explained by the differences in cooling rate along the diameter. Based on the physical characteristics of the bullets and on the obtained results, it can be concluded that one of the bullets could have been used as a grapeshot projectile and the other one as a bullet for ribauldequins. In addition, calcined ore and slag found in this factory were also analysed. The variation found in their chemical composition corroborated that the foundry temperature employed during the manufacturing process was low, the slag being enriched in Si, Al and Mn elements.
Open Access
Corrosion of cast aluminum alloys: a review
(MDPI, 2020-10-16) Berlanga Labari, Carlos; Biezma Moraleda, María Victoria; Rivero Fuente, Pedro J.; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
Research on corrosion resistance of cast aluminum alloys is reviewed in this article. The effect of the main microstructural features of cast aluminum alloys such as secondary dendrite arm spacing (SDAS), eutectic silicon morphology, grain size, macrosegregation, microsegregation, and intermetallic compounds is discussed. Moreover, the corrosion resistance of cast aluminum alloys obtained by modern manufacturing processes such as semi-solid and additive manufacturing are analyzed. Finally, the protective effects provided by different coatings on the aluminum cast alloys—such as anodized, plasma electrolytic oxidation (PEO), and laser—is reviewed. Some conclusions and future guidelines for future works are proposed.
Open Access
Effect of the temperature in the mechanical properties of austenite, ferrite and sigma phases of duplex stainless steels using hardness, microhardness and nanoindentation techniques
(MDPI, 2017) Argandoña Salinas, Gorka; Berlanga Labari, Carlos; Biezma Moraleda, María Victoria; Rivero Fuente, Pedro J.; Peña, Julio; Rodríguez Trías, Rafael; Mekanika, Energetika eta Materialen Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería Mecánica, Energética y de Materiales
The aim of this work is to study the hardness of the ferrite, austenite and sigma phases of a UNS S32760 superduplex stainless steel submitted to different thermal treatments, thus leading to different percentages of the mentioned phases. A comparative study has been performed in order to evaluate the resulting mechanical properties of these phases by using hardness, microhardness and nanoindentation techniques. In addition, optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been also used to identify their presence and distribution. Finally, the experimental results have shown that the resulting hardness values were increased as a function of a longer heat treatment duration which it is associated to the formation of a higher percentage of the sigma phase. However, nanoindentation hardness measurements of this sigma phase showed lower values than expected, being a combination of two main factors, namely the complexity of the sigma phase structure as well as the surface finish (roughness).
Open Access
Hydrophobic and corrosion behavior of sol-gel hybrid coatings based on the combination of TiO2 NPs and fluorinated chains for aluminum alloys protection
(MDPI, 2018) Rivero Fuente, Pedro J.; Maeztu Redin, Juan Deyo; Berlanga Labari, Carlos; Miguel, Adrián; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, Navarre-PRO-UPNA18-6107-FRRRIO
In this work, layers of a sol-gel hybrid matrix doped with metal oxide nanoparticles (TiO2 NPs) have been deposited on flat samples of AA6061-T6 aluminum alloy using the dip-coating technique, with the aim of obtaining coatings with better anti-corrosive and hydrophobic properties. Two different organic modified silica alkoxides, namely 3-(glycidyloxypropyl)trimethoxysilane (GPTMS) and methyltriethoxysilane (MTEOS), have been used for an adequate entrapment of the metal oxide nanoparticles. In addition, a fluorinated metal-alkoxide precursor has also been added to the hybrid matrix in order to improve the hydrophobic behavior. The experimental results corroborate that the presence of these TiO2 NPs play an important role in the development of the sol-gel hybrid coatings. The water contact angle (WCA) measurements, as well as pencil hardness tests indicate that TiO2 NPs make a considerable increase in the resultant hydrophobicity possible, with better mechanical properties of the coatings. The coating thickness has been measured by cross-section scanning electron microscopy (SEM). In addition, a glow discharge optical emission spectroscopy (GD-OES) analysis has been carried out in order to corroborate the adequate entrapment of the TiO2 NPs into the sol-gel coatings. Finally, potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) have been performed in order to evaluate the corrosion resistance of the coatings. All the results provide insights into the efficacy of the developed sol-gel hybrid coatings for anticorrosive purposes with good mechanical properties.
Open Access
Effect of Ti on microstructure, mechanical properties and corrosion behavior of a nickel-aluminum bronze alloy
(ABM, ABC, ABPol, 2021-04-12) Rivero Fuente, Pedro J.; Berlanga Labari, Carlos; Palacio, José F.; Biezma Moraleda, María Victoria; Ingeniería; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2
Nickel-aluminum bronze (NAB) alloys are suitable, in cast condition, to be used in marine propellers due to its excellent behavior avoiding erosion and cavitation as well as corrosion. A complex microstructure, intrinsic to this copper base system, is the result of a well-controlled chemical composition. There are few works related to the effect of adding small quantities of specific chemical elements on NAB alloys properties. The aim of this paper is to study the effect of Ti on the microstructure, mechanical properties, and corrosion behavior of a particular NAB alloy, CuAl10Fe5Ni5 (C95500), and the comparison to the Ti-free NAB alloy. Although the as- cast microstructure is very similar for both materials, the addition of only 120 ppm Ti leads to a significant grain refinement that plays a key role on the mechanical properties. It has been observed an increase in both microhardness and nanohardness as well as in the resultant Young moduli values, meanwhile no significant impact on the corrosion susceptibility has been observed.
Open Access
Using the multi-response method with desirability functions to optimize the zinc electroplating of steel screws
(MDPI, 2018) Lostado Lorza, Rubén; Martínez Calvo, María Ángeles; Berlanga Labari, Carlos; Rivero Fuente, Pedro J.; Institute for Advanced Materials and Mathematics - INAMAT2
Zinc electroplating is a coating process controlled by several input process parameters. However, the commonly used input parameters for setting the process of zinc deposition are current density, temperature of the coating solution, zinc concentration, deposition time, and concentration of additives (conditioner and brightener). The power consumed in the zinc plating process, coating thickness, increase in coating mass, and corrosion resistance are considered to be outputs or zinc coating parameters. They are widely used when the zinc coating requirements are based on the coating process cost, coating process speed, corrosion resistance, and coating thickness. This paper seeks to determine regression models by the response surface method (RSM) that relate the zinc coating parameters to the input parameters in steel screws. When considering the coating requirements of cost, coating process speed, corrosion resistance, and coating thickness, the optimal input parameters were found by using a multi-response surface (MRS). Input parameters of 0.3 amps/dm(2), 20.0 degrees C, 13.9 g/L, 45 min, 28.5 mL/L, and 2.8 mL/L, respectively (relative to the commonly used input parameters detailed above), were obtained when considering the cost. Considering minimization of the deposition time, the input parameters obtained were 0.5 amps/dm(2), 24.6 degrees C, 13.9 g/L, 45 min, 26.9 mL/L, and 1.1 mL/L, respectively. The optimal inputs to maximize the corrosion resistance were 0.6 amps/dm(2), 32.4 degrees C, 14.0 g/L, 45 min, 28.7 mL/L, and 2.5 mL/L, respectively. Finally, when maximizing the coating thickness, the inputs were 0.7 amps/dm(2), 38.4 degrees C, 12.2 g/L, 45 min, 26.5 mL/L, and 1.5 mL/L, respectively.
Open Access
Functionalized electrospun fibers for the design of novel hydrophobic and anticorrosive surfaces
(MDPI, 2018) Rivero Fuente, Pedro J.; Yurrita Silanes, David; Berlanga Labari, Carlos; Rodríguez Trías, Rafael; Ingeniaritza; Institute for Advanced Materials and Mathematics - INAMAT2; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa, Navarre-PRO-UPNA18 (6107)
In this work, a novel coating was deposited on aluminum alloy samples by using a combination of electrospinning and chemical vapor deposition (CVD-silanization) techniques in order to create a functionalized film with an enhancement of both corrosion resistance and hydrophobicity. The electrospinning technique makes the fabrication of highly crosslinked electrospun fibers possible by the combination of both poly(acrylic acid) and beta-cyclodextrin, respectively, which can be easily functionalized in a further step by using the CVD-silanization process due to the evaporation of a hydrophobic molecule such as 1H,1H,2H,2H-Perflurodecyltriethoxysilane. In addition, the resultant electrospun fibers with a high degree of insolubility have been successfully fabricated and metal oxide nanoparticles (TiO(2)NPs) have been incorporated into the electrospun polymeric solution in order to improve the corrosion protection. The surface morphology has been determined by using light optical microscopy, atomic force microscopy, scanning electron microscopy, and water contact angle (WCA) measurements. The corrosion resistance has been evaluated by using both potentiodynamic polarization and pitting corrosion tests. Finally, the results related to WCA measurements after CVD-silanization corroborate that the surfaces have been successfully functionalized with a hydrophobic behavior in comparison with the electrospinning process, showing a considerable difference in the roughness.