Sulfuric acid anodizing assisted by a hydrothermal sealing with inhibitors [Ce³⁺-Mo⁶⁺] was used to prevent pitting corrosion on spray-deposited hypereutectic Al–Si alloy (A390). An investigation concerning the evaluation of pitting corrosion resistance on the anodic oxide thin film with ions incorporated was carried out in NaCl solution using electrochemical measurements (i.e., potentiodynamic polarization and electrochemical impedance spectroscopy, EIS). The influence of Si phase morphology and size on the growth mechanism of an anodic oxide film was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results were then compared with those for its equivalent IM390 alloy (Al-17Si-4.5Cu-0.6Mg) produced through a conventional process ingot metallurgy, IM. The electrochemical findings indicate that sulfuric acid anodizing followed by a simple hot water sealing treatment was ineffective. In this manner, an intense attack was localized by pitting corrosion that occurred on the anodic oxide film in less than three days, as denoted by characteristic changes in the EIS spectra at the lowest frequencies. Improved results were achieved for Ce–Mo surface modification, which can provide better corrosion resistance on the aluminum alloys because no signs of pits were observed during the corrosion testing.

The geothermal steam turbines are exposed to mechanisms of corrosion/erosion that weakens its components and reduces their useful life. Due to this problem work has been done in application and characterization of coating in solid state by means of the technique of high-velocity Oxygen Fuel (HVOF), evaluating the corrosion rate (Vcorr) at high temperature of MCrAlY and Diamalloy 4006 coatings deposited on stainless steel SS304. Test was performance in an Autoclave at 1700C using a modified geothermal fluid as electrolyte. Open circuit potential was monitoring during 24hours until the system reached the equilibrium. After that, Polarization and Impedance Spectroscopy techniques were used to evaluate the specimens. For microstructure characterization; X–ray Diffraction (XRD), electron sweep microscope (SEM) and Optical microscope were applied. Results show that both coatings (Diamalloy 4006 and MCrAlY), have low current density compare with the substrate, which is an indicative of a lower corrosion rate due to the passive behavior of the species deposited on the Surface of the coating

La corrosión es uno de los principales problemas del deterioro en componentes, herramentales, equipos e inclusive a nivel estructural, ejemplo de esto son los aceros al carbono. En el presente trabajo se estudió la capacidad de inhibición a la corrosión de un extracto orgánico biodegradable proveniente de la planta del Nopal (Opuntia ficus-indica) para la protección del acero al carbono tipo AISI 1018, al agregar el 50% v/v del extracto de Nopal (EN) en una solución de H2SO4 (0,6 mol.l-1). Se utilizaron las técnicas de Resistencia a la Polarización (LPR) y Espectroscopía de Impedancia Electroquímica (EIS) para determinar la eficiencia de inhibición (IE) a temperatura ambiente durante 24 h y obtener las velocidades de corrosión (Vcorr), posteriormente se llevó a cabo la evaluación metalográfica para registrar el daño superficial. Los resultados mostraron una reducción de la Vcorr con una IE máxima del 84% al adicionar el inhibidor orgánico EN.

Soluble extract from Opuntia ficus-indica (Nopal extract) has been proposed in this chapter as a green inhibitor due to its component called mucilage, which has the ability to retain water; for this reason, it has been used as metal corrosion protection in machinery pieces, tools and other metallic components that need to be stored for short periods. In this way, three industrial carbon steels (AISI 1018, 1045 and 4140) have been exposed in sulfuric acid (H2SO4) to evaluate the corrosion behavior with or without Nopal extract (NE). Some electrochemical techniques have been implemented to evaluate the corrosion inhibition efficiency (IE) such as DC linear polarization resistance (LPR) and AC electrochemical impedance spectroscopy (EIS). Results indicated a considerable superficial modification of steel in terms of dielectric constant and ion charge capacity. When the NE was added, the corrosion mechanism changed from localized to general attack, decreasing the corrosion rate in all cases. More susceptibility to fail by corrosion was observed in the 1045 carbon steel in comparison with the other two studied steels; these results were confirmed by the percentage of inhibitor’s efficiency of about 95%.

In the present research work, the corrosion inhibition capacity of a liquid extract based on Citrus X-Latifolia leaves was evaluated as a green inhibitor that complies with a natural, economical, and environmentally friendly option. The tests were carried out on a carbon steel AISI 1045 exposed to an acid corrosive medium of 10 mL H2SO4 (0.5 M) to which various concentrations of the extract were dosed as follows: 40, 80, 120, 160, 200, 240, 280, 320, 360 and 400 ppm under standard conditions. Characterization by FT-IR was carried out to detect functional groups of the extract. The inhibitory behavior was recorded by electrochemical techniques (Tafel polarization and EIS). Finally, optical microscopy was used to evaluate the corrosion morphology. The results reveal that the adsorption of the extract molecules on steel follows the behavior of a Langmuir isotherm, reaching a maximum efficiency of 89 % with a concentration of 400 ppm. Finally, an evident change in the surface morphology of the steel sample is observed, thus reducing the pitting corrosion attack on AISI 1045 steel. Resumen. En el presente trabajo de investigación se evaluó la capacidad de inhibición de la corrosión de un extracto líquido a base de hojas de Citrus X-Latifolia como inhibidor verde que cumpla como una opción natural, económica y amigable con el medio ambiente. Los ensayos se realizaron sobre un acero al carbono AISI 1045 expuesto a un medio ácido corrosivo de 10 mL de H2SO4 (0,5 M) al que se dosificaron diversas concentraciones del extracto: 40, 80, 120, 160, 200, 240, 280, 320, 360 y 400 ppm en condiciones estándar. Se realizó una caracterización por FT-IR para detectar los grupos funcionales del extracto. El comportamiento inhibitorio se registró mediante técnicas electroquímicas (polarización de de Tafel y EIS). Finalmente, se utilizó microscopía óptica para evaluar la morfología de la corrosión. Los resultados revelan que la adsorción de las moléculas del extracto sobre el acero sigue el comportamiento de una isoterma de Langmuir, alcanzando una eficiencia máxima del 89 % con una concentración de 400 ppm. Finalmente, se observa un cambio evidente en la morfología superficial de la muestra de acero, reduciéndose así el ataque de corrosión por picaduras en el acero al carbono 1045.