The effect of Opuntia ficus-indica (Nopal) as green corrosion inhibitor for carbon steel in 1 M HCl solution has been investigated by using weight loss tests, potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. Also, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis were performed. The inhibitor concentrations used ranged from 0 to 300 ppm at 25, 40, and 60 ∘ C. Results indicated the inhibition efficiency increases with increasing extract concentration and decreases with the temperature, and the inhibitor acted as a cathodic-type inhibitor which is physically absorbed onto the steel surface. In fact, the adsorption of the inhibitor on the steel surface follows the Langmuir adsorption isotherm, indicating monolayer adsorption. The presence of heteroatoms such as C, N, and O and OH groups were responsible for the corrosion inhibition.

ZnO-based ceramic varistors have shown excellent electrical and dielectric properties due to their characteristics microstructures represented by the arrangement of their grains and grain boundaries that allow the absorption and flow of energy when subjected to an electrical surge. Their properties and characteristics depend on their chemical compositions and processing routes. Typical processing routes involve several stages of grinding and precalcination—which are time consuming processes. Because of this, this study proposes a simpler and cheaper alternative route for processing ceramic varistors. The alternative process proposed is the mixing of the precursor oxides by means of a hydrothermal treatment. The characteristics and properties of the synthesized ceramic varistors were evaluated by means of scanning electron microscopy, X-ray diffraction and impedance spectroscopy, considering the effect of the addition of rare earth oxides (La2O3, CeO2 and Nd2O3). The results showed that the mixing of the oxides through hydrothermal treatment produces ceramic varistors with characteristics and properties similar to those obtained by other processing routes. Furthermore, it was observed that the addition of rare earth oxides affects the characteristics and properties of the ceramic varistor depending on the type of rare earth oxide added, its concentration and ionic radius.

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The effect of Fe addition on martensitic transformation temperatures and electrochemical behavior was studied in polycrystalline Ni 51.4 Mn 24.8-X Ga 23.8 Fe X alloys (1˂x˂2.2) and Co 38.3 Ni 32.1 Ga 29.6 as alternative to Ni-Mn-Ga alloys which are used as ferromagnetic shape memory alloys. The analysis of corrosion rates was conducted by cyclic polarization curves with potentiostat-galvanostat equipment. The corrosion morphologies were also analyzed by scanning electron microscopy (SEM). The kinetics of corrosion was found to decrease with increasing Fe content in the alloy, while the martensitic transformation temperatures increased with increasing Fe content. The Co 38.3 Ni 32.1 Ga 29.6 alloy shows i corr lower than the Ni-Mn-Ga alloy. From results, the studied alloys exhibited a general dissolution in the anodic branch where a spontaneous passive zone occurred at certain potential and some elements like Co, Mn and also Ni were present in a higher percentage in corrosion deposits.

Hardfacing is a widely used method to service life extensión of the surfaces in continuous caster rolls subjected to severe wear, corrosion or oxidation. Martensitic stainless steels within the 12 % chromium alloys are the most used steels to hardfacing, nitrogen can be added to for cladding applications as an to carbon sustitute to increase hardness and form austenite at elevated temperatures [1,2]. The Heat input (HI) is one of the important variables refers to quality of the welding. Due to the heat input and the slow cooling rate occurs after welding, detrimental residual stresses are generated to the mechanical properties and / or corrosion in service. The leading steel companies in the world are located in coastal areas, where the continuous caster rolls are subject to corrosive environments as seawater. This work studies electrochemical corrosion behavior of martensitic stainless steels in synthetic seawater deposited as hardfacing, weldment have been obtained using an automatic flux-cored arc welding process (FCAW). The rolls were surfaced with a 414N-O tubular wire, a nitrogen-bearing, low-carbon wire that produces a martensitic deposit with a composition optimized for corrosion resistance. Figure 1, shows EDS result after the electrochemical test in seawater, can be seen of product obtained has concentrations of oxygen, chromium and iron. Figure 2, shows XPS result of corrosión products, where can see shape and composition of O 1s core-level spectra, presence of oxide, (oxy)-hydroxide, and water can be deduced from O 1s peak fit. Peaks at ~540 eV originate from molecular oxygen (O2) due to ambient air. Shape of Fe 2p core-level spectra, where presence of oxide, (oxy)-hydroxide, and metallic iron can be deduced from Fe 2p3/2. Shape of Cr 2p core-level spectra, where presence of oxide, hydroxide, and metallic Cr 0 can be deduced from Cr 2p3/2 [3]. Can be concluded that Fe is found as oxide while oxy-hydroxides appear combined with Cr and Fe.References:[1] Agustín Gualco et al, Materials and Design 31