Portugaliae
Electrochimica Acta

The acid corrosion inhibition process of copper in 2 M H3PO4, containing 0.3 M of NaCl by an eco-friendly ionic liquid, 1-pentyl pyridazinium bromide (PPB), has been investigated using weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).The effect of temperature on the corrosion behavior with the addition of PPB was studied in the temperature range 298–328 K. The value of inhibition efficiency decreases slightly with the increase in temperature. Results show that PPB is a good inhibitor and inhibition efficiency reaches 91 % at 10-3 M. Gravimetric essays indicate that PPB inhibits the corrosion of copper and the value of inhibition efficiency reaches 90 % at 10-3 M of the inhibitor. Potentiodynamic polarization curves showed that the PPB affects both cathodic and anodic current and may be classified as a mixed type inhibitor in (2 M H3PO4 + 0.3 M NaCl). For the inhibitor, the inhibition efficiency increased with an increase in the concentration. The adsorption of this compound on copper surface obeys Langmuir’s adsorption isotherm. To elaborate the mechanism of corrosion inhibition, the kinetic and thermodynamic parameters for copper corrosion and inhibitor adsorption, respectively, were determined and discussed. Inhibition efficiency values obtained from weight loss, polarization curves and EIS are reasonably in good agreement. Theoretical calculations provide good support to experimental results.

In this paper, an efficient artificial neural network (ANN) model using multi-layer perceptron (MLP) philosophy has been proposed to predict the fireside corrosion rate of super heater tubes in coal fire boiler assembly, using operational data of an Indian typical thermal power plant. The input parameters comprise coal chemistry, namely, coal ash and sulfur contents, flue gas temperature, SOX concentrations in flue gas, fly ash chemistry (wt% Na2O and K2O). An efficient gradient based network training algorithm has been employed to minimize the network training errors. Effects of coal ash and sulfur contents, wt% of Na2O and K2O in fly ash and operating variables such as flue gas temperature and percentage excess air intake for coal combustion on the fireside corrosion behavior of super heater boiler tubes have been computationally investigated and parametric sensitivity analysis has been undertaken. It has been observed that ash and sulfur contents of coal, flue gas temperature and fly ash chemistry have a relatively predominant influence on the rate of fireside corrosion with respect to other parameters. Quite good agreement between ANN model predictions and the measured values of fireside corrosion rate has been observed, which is corroborated by the regression fit between these values.

The corrosion inhibition efficiency of Capparis spinosa (CS) extract on the corrosion of copper in a 1.0 M NaOH solution was investigated using weight-loss, polarization and potentiodynamic corrosion rate measurements. The weight-loss showed that the inhibition efficiency of CS extract increased when increasing concentrations of CS extract and the immersion time. Maximum inhibition efficiency was 85%, which was obtained at 440 ppm of the CS extract at 45 °C in 1.0 M NaOH. Polarization measurements showed that the CS extract acts as a mixed type inhibitor. The cyclic voltammetry and potentiodynamics measurements suggested that the adsorbability of CS extract on copper was a bulk process, since surface coverage increased when increasing the concentration of CS extract. Thermodynamic measurements showed that the adsorption of CS extract on copper was physical, spontaneous, and favored at high temperatures. The adsorption of the inhibitor on a copper surface was in accordance with the Langmuir adsorption isotherm.

The corrosion inhibition characteristics of essential oil of mentha pulegium leaves have been studied as a green inhibitor of corrosion of aluminum in 2 M phosphoric acid using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The effect of inhibitor concentration shows that efficiency increases with increase of concentration with maximum of 79% at 1800 ppm. Polarization curves reveal that the essential oil of mentha pulegium leaves acts as a cathodic inhibitor. The effect of temperature on aluminum corrosion behavior was also studied and thermodynamic data of activation was determined.

Since its inception, the utilization of electroless nickel coatings in industries has increased by leaps and bounds, due to their excellent mechanical/electrical properties, hardness, high corrosion and wear resistance and low coefficient of friction. Their behavior in lubricated environments is an interesting subject of research and needs more attention. In the present study, the wear behavior of electroless Ni-P coating under lubricated condition has been investigated. Electroless Ni-P coating has been deposited on mild steel substrate. Characterization of the deposited Ni-P coating has been done using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyzer and X-ray diffraction (XRD) technique. A prediction model for the wear depth of the deposits with varying normal load, sliding speed and sliding time has been developed using multiple regression analysis and fuzzy logic, which is a very efficient artificial intelligence technique for modeling and monitoring systems. Experiments are carried out according to Taguchi’s L27 orthogonal array of experiments. The results obtained from the prediction models are seen to be in good agreement with experimental results. The applied normal load and sliding time are found to have a significant influence on the wear of electroless Ni-P coating. The wear mechanism was found to be mild abrasive in nature.