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.

Nickel aluminides have been extensively studied in recent decades to replace superalloys, in some components of aircraft turbines, because they have excellent corrosion resistance. Many industrial cities have the problem of air pollution, which has forced the study of the degradation of these alloys in the presence of acid rain. The aim of this work is to study the electrochemical corrosion behavior of nickel aluminides in a medium of simulated acid rain. Potentiodynamic Polarization, Linear polarization resistance curves, Rp, Nyquist data and Bode curves obtained by electrochemical impedance spectroscopy were used to study the corrosion behavior of two intermetallic compounds. The polarization curves show that both intermetallic Ni 3 Al and NiAl have very similar corrosion potential, showing a slightly nobler behavior the NiAl intermetallic. The intermetallic Ni 3 Al has an active-passive behavior where the anode branch presents a general dissolution of the alloy, indicating that it is under cathodic control. NiAl intermetallic shows an active dissolution region, followed by a passive behavior. At longer immersion times, Ni 3 Al intermetallic has a higher polarization resistance, which means a lower corrosion rate.

No abstract

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

En el proceso de colada continua, los rodillos se utilizan para la contención, soporte, conducción y transporte de la losa. Para extender substancialmente la vida útil de los rodillos, la superficie está cubierta con una capa resistente al desgaste llamada revestimiento duro el cual es aplicado por medio de soldadura de recargue, para mejorar las superficies que se encuentran sometidas a desgaste severo, oxidación o corrosión de los rodillos. El objetivo del presente trabajo es estudiar el efecto del aporte térmico por medio de técnicas electroquímicas de un acero inoxidable martensítico 414N aplicado como revestimiento duro en agua de mar sintética. El proceso de soldadura para la aplicación de los recargues fue por medio de soldadura de arco con electrodo tubular (FCAW) variando el voltaje del arco. Las técnicas electroquímicas fueron polarización potenciodinámica (PP) y espectroscopia de impedancia electroquímica (EIS). Los resultados indican que todos los recargues presentan una estructura martensítica de listón, donde 26 V presentó un 5.44% de ferrita, 28 V 5.33% y 30 V 5.0%, se puede observar que con un alto aporte térmico empleado se obtiene la menor cantidad de ferrita. De los resultados electroquímicos se puede observar, para 30 V se tiene el comportamiento más activo teniendo un Ecorr de -535 mV/ECS, siendo para 26 V y 28 V los valores más nobles (-380 mV/ECS y -425 mV/ECS) respectivamente. Para los 28 y 30 V se presentan potenciales de ruptura de la pasividad (313 mV/ECS y 132 mV/ECS) respectivamente.