مجله علوم و مهندسی خوردگی
سال یازدهم شماره 2 (پیاپی 40، تابستان 1400)

In this research, the corrosion inhibition of Citrus Aurantium peel extract as a green and environmentally friendly inhibitor on the corrosion of mild steel in 1 M sulfuric acid media has been investigated. The studies were evaluated using weight loss (WL), electrochemical impedance (EIS) and potentiodynamic polarization (PDP) methods. And all the tests were in good agreement and showed that the efficiency increases with increasing concentration of inhibitor. EIS showed that the Citrus Aurantium peel extract formed a protective layer on the metal surface and a yield of 98% was achieved using 1500 mg / L inhibitor. Polarization curves showed that the inhibitor affects both anodic and cathodic reactions and inhibitor is a mixed inhibitor. Thermodynamic and adsorption studies showed that the inhibitor adsorption on the surface follows the Langmuir adsorption isotherm model and the adsorption is spontaneous both physically and chemically. Also, the chemical properties of green inhibitor were investigated by FTIR, which shows the presence of O and N and aromatic groups in Citrus Aurantium peel as effective factors in corrosion inhibition.

In this article, reflection coefficient of ultrasonic guided waves from surface of a circumferential corrosion is evaluated to find the relation between this coefficient and the size of defect. In the present work, firstly, by solving the governing equations of the wave propagation with general matrix method and according to the boundary conditions in the pipe, dispersion curves of the phase velocity and group velocity were obtained, then simulation of wave propagation was performed using Abaqus finite element software. In this method, a longitudinal L(0,2) mode, which has good frequency characteristics, was used to generate the wave in the pipe. After determining the convergence, the wave propagation was carried out in the pipe with different dimension of defect. It was observed that part of the generated wave after collision to defect was reflected and various modes were generated that the first reflected mode was L(0,2) and the second reflected mode according to the group velocity dispersion curves of different modes was F(1,2). Different reflection coefficients were obtained due to different dimension of defects, and it was observed that with increasing defect depth, the reflection coefficient of the reflected wave also increased. In this article, the effect of circumferential corrosion width on the reflection coefficient of longitudinal wave has been investigated and it has been observed that the reflection coefficient of waves depends only on the depth of the defect and does not change much with the change of circumferential corrosion width.

Every year, a large amount of water is wasted due to corrosion of transmission lines, in a situation where we always face the problem of water shortage. The importance of transferring and distributing various types of industrial water such as drinking water, utility water, fire water, deionized water and cooling water is not hidden from anyone. Internal corrosion of water pipes has been considered as one of the industrial problems and their control has always been considered according to the importance of the issue. Lack of proper control and maintenance of systems from a corrosion point of view imposes huge costs on humans, industry and the environment. In this study, the amount of sedimentation, corrosion and root cause of water discoloration in the distribution and distributing network of drinking water in one of the refineries of Iran has been evaluated. Methods such as field evaluation, sampling, macrography, chemical analysis of water, mathematical relations, calculation of water indices and statistical analysis have been used to answer this question.

This research has been to investigate the cause of the stress corrosion cracking on dryer equipment (2DR-1745 & DR-1402) in Shahid Tondguyan Petrochemical Company (STPC). This dryer is as a drying powder Terphetalic acid in CTA2 and CTA1 units. After passing through RVF equipment wet cake moisture content of about 14% and temperature of 90C changed in to dry cake with a moisture content of less than 0.1% and the final temperature of about 140C and sent out Final Silos. After declaration of the operation department concerning the observation of acid leakage under the primary insulation was decided that at the first opportunity, this issue must be investigated. So, after the shutdown of unit and after washing the dryer wall, insulation around wall opened and it was found crack and leakage from some points.

Increasing the thickness of the oxide layer on the surface of the titanium alloy by electrochemical processes such as anodizing, leads to improved corrosion resistance and ultimately increase the lifespan of titanium implants in the human body. Among the parameters affecting the properties of the anodized layer, process voltage is of great importance with respect to kinetic and thermodynamic processes. In this paper, titanium substrate is subjected to anodizing process in sulfuric acid solution by different voltages such as 3, 6, 9 and 21 volts, electrolyte temperature of 60 ° C and duration of 30 seconds. Then the fuzzy, structural and morphological behavior, as well as the corrosion behavior of the coating are evaluated by GIXRD, FESEM and electrochemical tests such as electrochemical impedance in the simulated body fluid (SBF) solutionat 37 °C, respectively. GIXRD and FESEM analyzes show the formation of a titanium oxide coating with a hexagonal structure, which with increasing voltage up to 6 volts, a smoother and smoother surface was obtained, but further increase of voltage up to 9 and 21 volts, resulted in a rougher surface. Also, the results of corrosion behavior showed that increasing the anodizing voltage up to 6 volts due to the presence of a more uniform and smoother surface, which indicates less surface imperfections, led to the highest load transfer resistance in 1 and 24 hours of immersion in SBF solution at 37354 And 58127 (Ω .Cm2 ) compared to other anodized samples.

Conventional and vacuum heat treated nanostructured NiCrAlY coatings were applied using the high-velocity oxy-fuel (HVOF) process. The microstructural examinations of the as-received and nanostructured powders as well as their developed coatings were then analyzed using field emission scanning electron microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) analyses. For investigating oxidation behavior, the coated specimens were subjected to isothermal oxidation testing at 1050 ºC up to 5 h under air atmosphere. The results indicated that the nanostructured NiCrAlY coating has a lower oxide growth rate compared with the conventional coating due to the controlling the diffusion of Al-ions by the higher volume fraction of grain boundaries in the coating structure.