Papers by Keyword: Corrosion

Abstract: The deterioration of concrete from acid corrosion is a common issue in various industrial and natural environments. To address this problem, coal fly ash and bagasse fly ash were utilized as cement replacements in concrete. This study investigates the effects of these ashes on concrete's ability to withstand organic acid corrosion in depth, including a thorough examination of their chemical compositions, physical properties, and interactions within the concrete matrix. Furthermore, the research involves adjusting the blend proportions to provide exceptional resistance to acid corrosion. The results of the study highlight the significance of coal fly ash and bagasse fly ash in improving concrete's resistance to organic acid corrosion. The use of these materials as cement replacements significantly enhances concrete's resistance to organic acid corrosion, and this improvement becomes more apparent as substitution rates increase. This effect is primarily attributed to increased pozzolanic reactivity, resulting in a reduction in calcium hydroxide concentration within the cement matrix.

Abstract: Surface and sub-surface related degradation of steels can be minimized using suitable surface coatings. High entropy alloys (HEA) are prominent and emerging materials among many coating materials. The current study investigates the effect of heat treatment of HEA coating on mechanical, metallurgical, and corrosion properties. The HEA coatings on SS304 steel were deposited using a High-Velocity Oxy-Fuel (HVOF) thermal spray process. The developed coatings were furnace heat treated at 700 °C, 900 °C, and 1100 °C, respectively, and their performance was benchmarked with the as-sprayed coatings. The metallurgical, mechanical, and microstructural analyses were performed using X-ray diffraction (XRD), Nanoindentation, Scratch test, and Field Emission Scanning Electron Microscope (FESEM) techniques. The corrosion response of the as sprayed and heat-treated coatings were recorded using a Potentiostat. The results indicated that as-sprayed coatings consisted of a single-phase BCC solid solution; however, the single-phase changed to a dual dual-phase system after heat treatment (BCC+FCC). The 900 °C heat-treated HEA coating exhibited superior mechanical and corrosion properties. But those characteristics started diminishing when the heat treatment temperature exceeded 900 °C. The introduction of the new FCC phase softened the coating, thereby leading to the evolution of microcracks in the coating. These micro-cracks acted as channels for electrolyte diffusion and further corroded the coatings. The current study surmised that HVOF-sprayed HEA coating should not be heat treated at above 900 °C.

Abstract: IIn a geothermal environment, cathodic protection is employed to improve resistance against corrosion fatigue. However, during the cathodic reactions under applied potential, hydrogen is generated and assimilated, leading to a reduced lifetime expectancy of high-alloyed steels. The corrosion fatigue mechanism of a standard duplex stainless steel X2CrNiMoN22-5-3 (1.4462) specimen loaded with hydrogen was studied in a corrosion chamber specifically designed for the purpose, surrounded by the electrolyte of the Northern German Basin at 369 K. The microstructural reactions resulting in hydrogen incorporation significantly decrease the number of cycles to failure of the specimen. This reduction is attributed to hydrogen enhancing crack propagation and causing early failure, primarily due to the deterioration of the mechanical properties of the ferritic phase rather than corrosion reactions or corrosive degradation.

Abstract: Electroless Synthesis of Nicle phosphate zirconium dioxide (EL NiP/-ZrO2) has been carried out with ZrO2 nanocomposite (50 to 160 nm and concentration 4 gpl) and randomly dispersed into an alkaline Ni-P electroless bath (pH 8.0). The deposited thickness of NiP/-ZrO₂ nanocoatings resting on mild steels (MS) substrate (AISI 1040 grade) is carried out to evaluate the surface morphology and elemental composition. The SEM, EDAX and XRD methods elucidated clear difference between Ni-P along with NiP/-ZrO₂ nanocomposite coatings. Moreover NiP/-ZrO₂ nanocoatings contain uniform burly of ZrO₂ nanoparticles like whitish globules. Further the as-coated Ni-P/-ZrO₂ nanocoatings revealed mostly amorphous structures, while in heated coatings (temperatures 150, 350, and 550 °C with pure Ar) as temperature rises, the amorphous structure transformed leisurely to crystalline structure. The microhardness values in Vickers-unit of the developed nanocomposite coatings are determined and it is found that for a particular load with increase of temperature microhardness as well as corrosion resistancealso increases. Keywords: Electroless; Corrosion; Ni-P/-ZrO2; nanocoatings; Microhardness

Abstract: Recently, civil engineering fields are seeking for the use of cost-effective, lightweight, durable, and environmentally friendly materials, giving less maintenance and providing long durability and resistance to hostile conditions. Therefore, there has been significant progress in the utilization of sophisticated composite materials as a reinforcement for various structural elements in the context of new construction buildings or rehabilitation.Fibre-reinforced polymer (FRP) are composite materials that have emerged as a potential method for enhancing the strength of concrete structures. FPR has been recommended for its many benefits, including thermal insulation properties, corrosion resistance ability, high tensile strength, fatigue resistance, and lightweight. Environmental deterioration increases the need for sustainable, durable, and mechanically sound reinforced concrete (RC) elements. Thus, geopolymer concrete (GPC) made from industrial byproducts like fly ash, slag, aluminum-rich materials, and the alkali activators (needed for alkaline solutions to activate the geopolymerization process) stands as a promising substitute for conventional Portland cement, owing to its engineering characteristics and sustainable nature (low CO2 emissions and industrial waste).In conclusion, Results discovred that the compressive strength of GPC can reach values of 70-100 MPa within 28 days. FRP-reinforced geopolymer concrete has a wide range of possible applications, however, there are still many barriers to commercializing FRP in the construction industry. Review indicated that the distinct properties of FRP bars embedded in GPC can provide a promising technology for the construction of new structures with high sustainability, sufficient strength, and structural integrity. Ductility ratios for GPC beams were 5% to 34% higher than those for reinforced OPC beams. Compared to steel-GPC beams, FRP-GPC beams deflect and fracture more due to their lower modulus of elasticity. Therefore, it is possible to use geopolymer concrete with a combination of steel bars and FRP in order to overcome the disadvantages of using only FRP or steel.

Abstract: Researchers continue to be concerned about corrosion of materials, which motivates them to start projects to address the harmful impacts of this phenomena that affects the desired function of our materials, especially in industries where acid is used in the process of cleaning machines. The purpose of this study is to reduce the corrosion rate of brass in 5M solution of H₂SO₄ acid using orange juice as inhibitor. The study was conducted using weight loss method. It was observed that for 24 hours the corrosion rate was higher for acid and decreased as the inhibitor was added. In all samples the corrosion rate decreases as the inhibitor were added, however improves over time. For 24 hours the efficiency was higher for acid + 100mil at 14% and it became constant after 48hrs at 32,7%. However, for 72 – 96 hours acid + inhibitor of 60mil there efficiency reported to be 54.3 and 56.4%. Keywords-orange juice, inhibitor, corrosion, acid, efficiency.

Abstract: Lightweight metallic alloys in the transport sector are the essential choice to reduce carbon monoxide emissions. Magnesium (Mg) can serve this purpose appreciably because it has a low density compared to other metallic metals and a high strength in a small portion of metals. The reason behind this is having very low weight. Notwithstanding the alloys exhibit high susceptibility to corrosion especially galvanic corrosion, which impedes it from its various applications. The corrosion resistance of magnesium alloy depends largely on the surface film whether it can protect well and the corrosion due to galvanic effect between the second phase particles or microstructures and the magnesium matrix. Role of second phase particles eventually improves the corrosion property by enhancing its resistance to corrosion. Mg-4Zn being a promising alloy, 3 wt% Gd has been added further to investigate the corrosion resistant properties of Mg-4Zn-3Gd alloy. After preparing the alloys by casting method in induction furnace followed by homogenization at 410°C, the sample was hot rolled at 400°C. Preparation of the samples has been verified by EDS, XRF and XRD analysis. Corrosion study has been done for 1 hour, 24 hours and 72 hours. Microstructures have been taken for as cast, homogenized, and as rolled condition before corrosion test. The analysis shows a large difference in the grain size and phase distribution. Due to dynamic recrystallization during rolling hardness also shows differences compared to as cast and homogenized sample. The corrosion test is performed by weight loss test, electrochemical measurement, and immersion test. In the results, it has been seen an increase in corrosion rate at the initial stage, however it came to a constant rate after some time. After corrosion test, optical micrographs (OM) and scanning electron microstructures (SEM) images show typical morphology of corroded surface with some micro cracks. The presence of Gd in Mg-4Zn alloy enhanced the corrosion performance when it is done for longer time.

Abstract: CO₂ levels in the world are constantly increasing and have generated a great impact on reinforced concrete structures causing increased carbonation. The phenomenon of carbonation causes corrosion of the reinforcing steel, therefore, reinforced concrete structures present a high risk of corrosion of its reinforcing steel causing the reduction of the useful life of the structure, or in extreme cases, a demolition must be carried out. The objective of the present study is to propose a prediction model for carbonation depth in pure concretes which are not designed for durability (w/c<0.50), but when they are designed for resistance (w/c>0.55). CEB-FIP model presents the limit of serving only for concrete with w/c<0.50, due to this, the present study proposes a model that will help as a reference to estimate the useful life of structures that are built and designed in cities where they do not are exposed to these durability conditions. The modified model for predicting the carbonation depth based on CEB-FIP in pure concrete with high w/c (0.60 and 0.72) uses the parameters of temperature, relative humidity, CO₂ concentration, and water/cement ratio. The objective is to obtain the accuracy of the modified model for predicting the carbonation depth in concrete over the years. For the results, the theoretical data obtained from the modified model was used and a comparison was made with the experimental results obtained from concrete specimens tested inside an accelerated carbonation chamber to find the model's accuracy.

Abstract: Zinc has attracted significant attention in research due to its cost-effective use as an electrodeposited material, effectively protecting various types of steel from corrosion and wear. However, despite its advantages, zinc has limitations in fully guarding steel against corrosion. Recent studies propose that blending zinc with other metals during the coating process can proficiently shield mild steel from deterioration. The motivation for this study stems from recognizing the restrictions of zinc electrodeposition and the limited exploration of zinc multi-facet composite coatings for mild steel. In this study, the electrodeposition technique was employed to apply a coating to mild steel using zinc and nanoparticles of calcium oxide (CaO) and manganese oxide (MnO₂). The coating bath's chemical composition included mass variations of 0-12 g/L for CaO and MnO₂, along with 10 g/L each of boric acid, thiourea, and Na₂SO₄, and 15 g/L of K₂SO₄ and ZnSO₄. The coating process occurred over a twenty-minute period, with a pH of 4.8, voltage set at 3.2V, current density at 1 A/cm², temperature at 47°C, and stirring rate at 200 rpm. Results obtained from the coated mild steel demonstrated that Zn-6CaO-6MnO₂ exhibited the greatest coating thickness at 0.2308 mm, and it showcased impressive corrosion resistance at 2.0618 mm/year. The Zn-CaO-MnO₂ coating displayed a substantial deposit of crystallites in its microstructure, assisted by the presence of manganese, contributing to a smoother surface texture.

Abstract: The crack initiation and propagation in an aluminium alloy in a corrosive environment are complex because of the loading parameters and material properties, which may result in a sudden failure in real-time applications. This paper investigates the fracture toughness of aluminium alloy under varying environmental and corrosion conditions. The main objective of the work is to link the interdependencies of humidity and temperature for an AL6082-T651 alloy in a corrosive environment. This study investigates AL6082-T651alloy's fracture behaviour and mechanism through microstructure and fractographic studies. The results show that a non-corroded sample, at room conditions, provided more load-carrying capacity than a corroded sample. Additionally, an increase in temperature improves fracture toughness, while an increase in humidity results in a decrease in fracture toughness.