In this study, the effect of the addition of Nd 3+ ions as a corrosion inhibitor of the API X70 steel in a medium rich in chlorides was evaluated. e performance of the Nd 3+ ions was evaluated by means of electrochemical techniques such as potentiodynamic polarization curves, open circuit potential measurements, linear polarization resistance, and electrochemical impedance spectroscopy, as well as by means of scanning electron microscopy and EDS measurements. e results showed that Nd 3+ ions reduce the corrosion rate of steel at concentrations as low as 0.001 M Nd 3+ . At higher concentrations, the inhibition efficiency was only slightly affected although the concentration of chloride ions was increased by the addition of the inhibitor. e adsorption of the Nd 3+ ions promotes the formation of a protective layer of oxides/hydroxides on the metal surface, thereby reducing the exchange rate of electrons. Nd 3+ ions act as a mixed inhibitor with a strong predominant cathodic effect.

The effect of Cu addition on the electrochemical corrosion behavior of Ni3Al intermetallic alloy was investigated by potentiodynamic polarization, open-circuit potential, linear polarization resistance, and electrochemical impedance spectroscopy in 1.0 M H2SO4solution. Performance of the pure elements (Cu, Ni, and Al) was also evaluated. In general, Cu addition improved the corrosion resistance of Ni3Al. Electrochemical measurements show that corrosion resistance of Ni3Al-1Cu alloy is lower than that of other intermetallic alloys and pure elements (Ni, Cu, and Al) in 1.0 M H2SO4solution at 25°C. Surface analysis showed that the Ni3Al alloys are attacked mainly through the dendritic phases, and Cu addition suppresses the density of dendritic phases.

The performance of different Cu-based coins in artificial sweat was evaluated. The electrochemical behavior of the coins was determined by potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. Regardless of the chemical composition of the Cu-based coins, they showed similar polarization curves; particularly, the observed similarity in the anodic zone suggests that the corrosion mechanism is the same in all cases. The presence of Ni and Zn does not appreciably affect the corrosion resistance of Cu. However, the presence of both elements affects the corrosion resistance of Cu. Electrochemical impedance spectroscopy measurements showed the presence of three time constants with very similar characteristics, again indicating that the main corrosion mechanism is the same in all cases. Equivalent circuits confirmed that the corrosion performance of the Ni-Zn-Cu coins depends on the Zn/Ni ratio, such that decreasing this value decreases the corrosion resistance of the alloy. In general, nickel has a detrimental effect due to the formation of highly soluble Ni-based corrosion products.

Due to its high content of rare earths, the use of permanent magnets can be a sustainable alternative for the synthesis of environmentally friendly corrosion inhibitors in order to replace the use of highly toxic inhibitors, as well as the use of rare earth salts of high purity and high cost. In this study, the recovery of rare earths from permanent magnet wastes and their synthesis to chloride salts were carried out. Rare earth chlorides were evaluated as corrosion inhibitors by electrochemical techniques on API X70 steel in a 3.5% NaCl solution. Both anodic and cathodic polarization curves were made, and measurements of both open-circuit potential, linear polarization resistance, and electrochemical impedance were made. Results show that the inhibitor synthesized is a mixture of Nd and Pr chloride. Its performance as a corrosion inhibitor is superior to that of high purity Nd chloride (analytical reagent). The results show that the use of electronic scrap is a sustainable source for the synthesis of green corrosion inhibitors with low carbon footprint.

Many alloys used at high temperature in industrial processes are Ni-based and many others contain it in appreciable quantities, so it is of interest to evaluate the performance of pure nickel in order to determine the behavior of its alloys once the elements responsible for their protection have been depleted due to accelerated corrosion processes in the presence of vanadium-rich molten salts. Due to this, this work presents the study of Ni behavior in NaVO3-V2O5mixtures at different temperatures. The behavior of pure nickel was determined by both electrochemical and mass loss measurements. The results show that the aggressiveness of the vanadium salts is increased by increasing both the V2O5content and temperature. V2O5addition considerably increases the current densities of the anodic and cathodic reactions. The corrosion process of Ni is modified due to the presence of its corrosion products, and its presence increases the activation energy by at least one order of magnitude. Although nickel shows a high reactivity in vanadium-rich salts, its reaction products are highly stable and protect it from the corrosive medium because the corrosion reactions trap the vanadium and block the migration of nickel ions.