مجله علوم و مهندسی خوردگی
سال دوازدهم شماره 2 (پیاپی 44، تابستان 1401)

Improving and optimizing corrosion protection methods, including cathodic protection, has received much attention in recent years. Due to the advancement of science and technology and industry development, manufacturing and controlling rectifiers has also made significant progress. The performance characteristics and efficiency of rectifier components have improved over the years. Based on the studies, an industrial pulse rectifier that can produce pulsed current in the frequency range of 800 Hz to 60 kHz based on the desired frequency and duty cycle was successfully designed and manufactured. In order to evaluate the protection performance of this system in the field, the pulse rectifier was placed next to the conventional rectifier, and the protection conditions of the system were continuously monitored. Three test points with specified intervals were analyzed at frequency and duty cycle of 50 kHz and 73% (A), 60 kHz and 73% (B), 60 kHz and 50% (C), and 50 kHz and 50% (D), respectively. Results showed that AC voltage in the pulse system has decreased by more than 80% compared to the conventional system. In addition, the current consumption values showed that in the pulse system, the current consumption has decreased by more than 70% in certain values of frequency and duty cycle. Because the pulse wave has practically no current consumption during off time, energy consumption is greatly reduced, an important factor in energy consumption and economic costs. Also, this system has no cooling system like the conventional rectifiers. Accordingly, the system has a better performance at certain values of frequency and duty cycle. Such systems in areas with high electrolyte resistance can be considered a good option. Also, if the pipeline has a cover, the system can function properly even with the cover separation areas. Moreover, the protection potential became more uniform and remained within the protection range during the measurement period, despite the poor performance of the anode bed.

The Ti/IrO2-Ta2O5 electrode was well performed as a mixed metal oxide for the oxygen evolution reaction. In the industry, the high price of its fabrication caused its utilization to be limited. In the present work, to reduce the cost, low-content IrO2-included electrode was used in producing electrodes so that they did not show lower performance for the catalytic oxygen revolution reaction. Ti/IrO2-Ta2O5-SiO2 electrode was prepared by the solgel method of iridium chloride, tantalum chloride, and tetra ethoxy orthosilicate salts at 430 C. Doping silicon oxide and tantalum oxide to the electrode increases the corrosion resistance in acidic media. The surface morphology of the electrode was evaluated by SEM and EDAX. Furthermore, the stability of the electrode was investigated for use as an anode in the electrowinning system of copper, in 0.5 M sulfuric acid at 30 C and under a constant current of 1.5 Acm-2 , as a function of the electrolysis time during the ALT. The results indicated that the prepared electrode had a stability of 173 h in the sulfuric acid solution. Moreover, the electrocatalytic activity of the electrode during the stability test was studied by the cyclic voltammetry. It was found that with the penetration of the electrolyte into the coating, the amount of electrical charge increased to 70.2 mC.cm-2 , whereas it decreased to 31.4 mC.cm-2 with the electrode degradation.

In this research, a two-component anti-corrosion coating based on polyurethane was made using polyacrylic resin and isocyanate hardener with different NCO/OH ratios. The anti-corrosion performance of these coatings was investigated using electrochemical impedance spectroscopy (EIS) with time in 1 M sulfuric acid. Equivalent circuit models were used to quantitatively compare the effect of the NCO/OH ratio on the anti-corrosion performance of polyurethane coatings. The results showed that with increasing the amount of hardener, the corrosion resistance of the coating first increases and then decreases and hence the best anti-corrosion performance of the coating was obtained at NCO/OH ratio of 1.2.

In this research, the corrosion resistance of weld metal in API-5L X90 micro-alloy steel joints was investigated. Welding was performed using filler metals ER120S-G, ER100S-G and ER90S-B3 by GTAW process. Microstructural studies were performed using light microscope and SEM scanning electron microscope. Microstructural studies showed that the base metal microstructure consists of ferrite and granular bentite. It was found that different weld metals all contain different amounts of accular Ferrite, polygonal ferrites and martensite / austenite (MA) islands. The highest amount of accular Ferrite was observed in ER 120 SG welding metal. The results of corrosion test showed that ER120SG welding metal and base metal had the lowest flow density and corrosion rate. And the highest corrosion rate was obtained for ER100SG welding metal.

To control the oxidation and hot corrosion behavior of nickel Incol 718C super alloy, used in jet engine blades, Sermaloy J penetration coating process, which is a type of aluminide coating modified with silicon and chromium, was applied by slurry method. The effect of variables including the percentage of chromium in the slurry, coating thickness (creation of several layers) and coating temperature were modeled and optimized by Minitab software and response surface methodology. Analysis of variance showed a good correlation coefficient for the proposed model (R2 = 96.9). Energy scattering and corrosion analyzes were performed the results showed that the possibility of penetration of chromium along with aluminum and silicon in the coating by slurry on nickel Incol 718C alloy improves the performance of the coating.

Corrosion occurs in many parts of the car and it is not only undesirable because of the problems it causes, but also reduces the resale value of the car and reduces the strength of the parts.The automotive industry is one of the important industries that are exposed to damages caused by corrosion reactions. All types of cars, due to exposure to atmospheric environment, polluting gases, and deicing salts, suffer total and partial damages in various components such as car body, internal engine components, radiator, battery, exhaust pipe, fuel tank, electrical systems, etc. Therefore, based on the importance of investigating various possible types of corrosion in automobiles, reviewing of other papers was performed in this paper. According to the statistics reported in the articles, the highest amount of corrosion is generally occured in the car engine and the type of corrosion is pitting or galvanic corrosion, although crevice and uniform corrosion can also occur in other parts of the car such as the car suspension system, fuel system, etc. Air humidity, pollutants type and content, surface humidity, and temperature can be mentioned among the factors affecting the amount and rate of corrosion in the automotive industry. It should be noted that the most common damages caused by corrosion in the engine parts include incomplete combustion and reduced efficiency, broken injectors, clogging of fuel and oil filters, as well as shorter life of used oil.