Papers by Keyword: Corrosion Rate

Abstract: Stress Corrosion Cracking (SCC) is a phenomenon in which cracks develop in certain materials due to a combination of stress and corrosion. This process is commonly observed in low-alloy steels with a ferritic-pearlitic structure, such as X70, which are often used in buried pipeline applications within the oil and gas industry. These materials are particularly susceptible to SCC failure in dilute solutions. To simulate SCC conditions, the Near-neutral simulated soil solution (NS4) has been established as a widely accepted industry standard for conducting crack growth experiments in many laboratories. This paper aims to investigate the role of electrochemistry in SCC under near-neutral soil solution conditions by presenting a numerical study using COMSOL on the effects of applied potential on corrosion rate in near-neutral soil solutions. According to the findings, the electrode thickness, current density, and corrosion rates were mostly affected by an applied potential of -1.2 V. This implies that slight modifications in the applied voltage can greatly influence the corrosion rate of the electrode. This outcome aligns with prior research on the influence of potential on electrode performance and emphasizes the crucial role of precise control of the applied potential in electrochemical systems.

Abstract: Concrete is a construction material that is extremely widely used in the construction of water management facilities. However, in the presence of hydrogen sulfide in the gas-air operating environment, concrete can undergo extremely aggressive biogenic sulfuric acid corrosion. The paper presents the results of an experimental chemical, physico-chemical and phase study of concrete samples from the surface part of the gravity sewage collector and the primary sump of the city sewage facilities and oil trap at the oil production site. It was proved that all concrete samples were subjected to biogenic sulfuric acid aggression, to the greatest extent – a sample from a city sewage collector.

Abstract: Al-Zn-based AMC is a light metal, with low density, excellent mechanical and mechanical properties, suitable for use in automotive, electrical, general-purpose electronics, machinery and equipment. However, the development of this alloy is limited by its low hardness and low corrosion resistance, which limits its use in many applications. This corrosion process can cause fitting corrosion and can damage the passive oxide layer that protects the metal from corrosion. This study aimed to increase the corrosion resistance of AMC Al-Zn by adding hydroxyapatite ceramic reinforcement from snail shells in a corrosive medium of 3.5% NaCl solution. The HAp is used as an AMC amplifier. AMC uses Al-Zn alloys with a ratio of 90% to 10% by mass. The variation of HAp enhancer used was 10, 15, 20, 30 and 40% by weight. This AMC was produced by powder metallurgy using 250 KPa compression for 20 min with sintering at 550°C for 2 h followed by slow cooling. The characterization of Al-Zn-based AMCs was performed by electrodynamic polarization testing in 3.5% NaCl solution. From the experimental results, the addition of HAp snail waste at a concentration of 20% by weight with matrix composition Al₉₀-Zn₁₀ is an AMC preparation with optimal corrosion resistance. The corrosion rate of Al₉₀-Zn₁₀/20HAp is 0.01 mmpy, while the corrosion rate of Al₉₀-Zn₁₀/0HAp is 1.15 mmpy. The addition of HAp up to 20% by weight showed the highest micro-hardness (117.90 Hv) while the smallest micro-hardness occurred at AMC Al₉₀-Zn₁₀/0HAp (87.57 Hv). The HAp material could very well be used as an AMC-reinforced biomaterial for biomedical applications.

Abstract: A well-known corrosion parameter is corrosion rate as measured by the electrochemical or the weight-loss methods. The weight loss methods can be measured continuously or intermittently depending on the actual conditions of sample placement and the experimental design. But what distinguishes the measurement method is whether they produce the same corrosion rate value or not. This study aims to study the corrosion rate with a continuous and discontinuous measurement method of weight loss using carbon steel specimens immersed in sodium chloride solution and further compare the two results. For this purpose, 25 sample coupons with the size of 80x23x3.6 mm have been prepared. The measurement of weight loss was carried out on specimens for 10, 20, 30, 40, and 50 days, by immersing the sample in 2 and 3%-wt NaCl, respectively, and one was treated in distilled water according to ASTM G31-72. From the three treatments studied, a percentage of the results was a value that lies between 2.67 and 5.46% with an average value of 4.17%. There is no significantly effect of the data collection method for the three types of the treatment samples immersed for 10 to 50 days in distilled water, 2 and 3%-wt sodium chloride solution.

Abstract: Magnesium (Mg) and its alloys have been intensively investigated as potential biocompatible materials with appropriate structural, mechanical and corrosion properties for preferable orthopedic applications. Selective Laser Melting (SLM) technique was developed for the fabrication of three-dimensional components with high structural integrity at a low cost and is compatible with various materials, including biocompatible magnesium alloys. In this study, WE43 magnesium alloy samples produced by SLM technique were examined by in vitro static test in Hank's balanced salt solution (HBSS) under physiological temperature conditions for six days. A hydrogen evolution method for the estimation of the corrosion rate was used. The phase composition of samples before and after the immersion test was investigated by X-ray diffraction (XRD). The surface morphology and chemical composition of the initial material and tested samples were characterized by scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDX).

Abstract: Corrosion behavior of 7A52 aluminum alloy plasma arc welding (PAW) joint was investigated in simulation of marine atmosphere environment with salt water spray test. The surface morphologies were observed by scanning electron microscopy (SEM), and the effect of corrosion time on corrosion behavior was discussed. The depth of spot corrosion, the corrosion dynamic characteristics, and the distribution of element of 7A52 aluminum alloy welding joint were analyzed by 3D and XRD Microscope. Results show that pitting corrosion is main morphology in heat effect zone at initial stage, pitting corrosion appears in matrix and welding joint with time. The main component compounds existing in the film include Al and O. The depth of pitting corrosion in the heat effect region is the maximum (3.008μm). The law of power function is followed in both phases of the corrosion weight increasing curve, and the corrosion rate decreases with time.

Abstract: Arachis hypogaea (AH) and Cocos nucifera (CN) surfactant were examined as corrosion inhibitor for 316L steel in 9 M HCl solution by weight loss (WL) method. Observation from the results showed that the presence of the active components and functional groups were actually the reasons for strong adsorption performance of AH and CN inhibitors as the corrosion rate was drastically retarded with increment in percentage inhibitor concentrations. Though AH inhibitor showed better efficiency than CN inhibitor due to more active components as revealed by the phytochemical analysis test. ATF-FITR test demonstrated all the potential functional groups accountable for the excellent inhibitions of AH and CN inhibitors. Keywords: Organic compound; Corrosion rate; Active components; Functional groups. ATF-FTIR spectroscopy.

Abstract: The application of aqueous extracts of leaves, stem and seed of Azadirachta indica as good green corrosion inhibitors of mild steels in 0.25 M hydrochloric acid (HCL) was evaluated. Extracts were prepared by evaporating the filtrate of the aqueous solution obtained from dried samples, hence, used for the preparation of inhibitor test solutions. Mild steel rods of 8 mm diameter were used. Phytochemical screening of aqueous leaf, stem and seed extracts of Azadirachta indica (Neem) and corrosion inhibition rates of the extracts in 0.25 M HCl were determined by gravimetric analysis. The weight loss was calculated after each measurement, the inhibitory efficiency (I%), corrosion rate (Cr) and surface coverage (θ) were calculated using mathematical relationships. The mechanism of inhibitor adsorption on the metal steel surface was studied using Langmuir adsorption isotherms. The results revealed that extracts of leaves, stem and seed of Azadirachta indica were effective at inhibiting the rate of corrosion on the mild steels in 0.25 M HCl medium. The effectiveness of the extracts as corrosion inhibitors was observed to be dependent on the concentration of the extracts. The extracts were most effective after 9 days exposure period with inhibition efficiencies of 94.22 % (leaves), 86.27 % (stem), 83.22 % (seed) at 1.0 g concentration, while at the end of the 15 days exposure period, 1.0 g concentration of the extracts produced the highest inhibition efficiency at 94.17 %, 86.18 % and 83.11 % for the leaves, stem and seed extracts respectively. The Langmuir isotherm was obeyed by the extracts. The findings of this study demonstrated that neem leaves, stem and seed aqueous extracts are good green corrosion inhibitors therefore, their use as corrosion inhibitors should be greatly encouraged.

Abstract: Ti-6Al-4V ELI is one of the titanium alloys commonly used as an implant material for its good biocompatibility. However, it has problems related to its corrosion behavior, especially when it is used for a long time. This study aimed to analyze the corrosion behavior of the implant material Ti-6Al-4V ELI in Hanks’ Balanced Salt Solution (HBSS) for a certain period, using the weight loss method in HBSS as the corrosive medium at 37°C. The immersion time was varied from two, four, until six weeks. Before immersion, the sample was thermomechanically treated with a combination of solution heat treatment at a temperature of 950°C and a holding time of 1 hour, water quenching, plastic deformation with deformation variations of 10%, 15%, and 20%, and, finally, aging heat treatment at a temperature of 550°C and holding time for 1.5 hours. The study results show that thermomechanical treatment and increased plastic deformation could reduce the corrosion rate and the metal ions released into the solution. These findings were evidenced by the corrosion rates of the pre-thermomechanical and the thermomechanical Ti-6Al-4V ELI with deformations of 10%, 15%, and 20% at the 6-week immersion of 6.57 x 10^-6 mmpy, 4.27 x 10^-6 mmpy, 3.89 x 10^-6 mmpy, and 2.76 x 10^-6 mmpy, respectively, and the metal ions released of 7.3 μg/L, 7 μg/L, 6.3 μg/L, and 6 μg/L, respectively. The corrosion rate of Ti-6Al-4V ELI under thermomechanical treatment, namely 2.76 x 10^-6 mmpy, was the lowest compared to other materials in HBSS, while the highest one was that of Ti-6Al-7Nb of 3.05 x10^-2 mmpy. In addition, the study results show that Ti-6Al-4V ELI under thermomechanical treatment is the best material compared to others for biomedical applications, based on corrosion resistance and metal ions released into HBSS.

Abstract: On the basis of the conducted theoretical and experimental studies, the dependences for determining geometric, physical and mechanical parameters of the surface layer quality, wear resistance and corrosion rate depending on the modes and conditions of electroerosion of machine parts are presented. They allow determining optimal modes and conditions of electroerosion to ensure the required parameters of the surface layer quality (with a two-stage approach it provides design and technological support of operational properties), wear resistance and corrosion rate (with a single-stage approach it makes direct technological support possible).