Papers by Keyword: Corrosion

Abstract: This study addresses the reinforcement of corroded API 5L X42 pipelines using Glass Fiber Reinforced Polymer (GFRP) composite wraps, focusing on optimizing fiber orientation to enhance burst pressure performance. Pipeline corrosion poses significant risks to structural integrity and safety in the oil and gas industry. Experimental burst pressure testing, and Finite Element Method (FEM) were conducted to evaluate unidirectional (0/0/0), bidirectional (0/90/0) and multi-axial (0/45/-45) GFRP wraps. The FEM model, validated against experimental data, showed minimal error with 1.16%. Major findings show that the bidirectional had a maximum stress (501.29 MPa) and burst pressure (44.72 MPa) higher than the unidirectional and multi-axial. Better stress distribution given by the bidirectional structure helped to lower stress concentrations. These results show that pipeline repair techniques can be much improved by orienting fibers correctly. This study found that it helpful in field application of composite repair techniques for corroded subsea pipes.

Abstract: In this study friction stir processing (FSP) was utilized to refine the microstructure of thick AZ31D magnesium (Mg) alloy, followed by evaluation of its microstructure and corrosion behavior in a NaCl environment. The application of a tapered threaded pin profile resulted in enhanced material mixing, significant grain refinement and reduced defect formation due to minimal heat input and minimized thermal gradients across the stir zone (SZ). The SZ, dominated by the pin profile, exhibited a fine, equiaxed, and uniform grain structure throughout its thickness the average grain size reduced from 13.8 µm to 5.19 µm after second pass of FSP confirmed through field-emission scanning election microscopy (FE-SEM) analysis. This structural refinement significantly enhanced the corrosion performance of the FSPed alloys, as compared to the base material (BM), demonstrated by electrochemical testing in 3.5% NaCl solution. The FSPed alloy surface showed uniform corrosion behavior, instead of intergranular corrosion with deep mud cracking patterns observed in the BM. This improved corrosion resistance was due to the uniformity of the produced microstructure via FSP, which reduced localised corrosion sites. These findings suggest that FSP is a promising technique for improving the durability of Mg alloys in corrosive environments, potentially benefiting applications in the automotive and aerospace industries.

Abstract: Reinforcing steel deterioration is complicated by corrosion. Reinforcing steel corrosion can weaken a structure. Corrosion cannot be eliminated; however, it can be reduced to increase building service life. The objective of the research it to demonstrate the effect of coating method as corrosion prevention and the cover depth to the corrosion performance of steel bar embedded in seawater mixed mortar. This study examines the corrosion rate of steel reinforcement in a 15 x 15 x 15 cm mortar cube made by using seawater as mixing water and containing Portland Pozzolan Cement (PPC) as a binder material. This study also experiences numerous corrosion mitigation methods using wet, dry, and dry-wet cycle exposure methods. The reinforcement and mortar surface were protected with anti-corrosive paint. Additionally, specimens without protective measures were also fabricated for comparison. Two reinforcing steels were attached in the two different cover depths, 3 cm and 5 cm. This study used sand and batching plant byproducts as fine aggregate. Study found a hierarchy of corrosion-causing exposures. The dry-wet cycle was the most corrosive, followed by wet and dry. Steel coating prevents corrosion better than surface coating. However, both methods outperformed the uncoated method in corrosion resistance. The mortar cover was 5 cm thick, compared to 3 cm expected. A combination of mortar with fine sand aggregate outperformed dry mortar made from batching plant leftovers. The investigation of corrosion potential through the utilization of the half-cell potential technique reveals that the outcomes obtained from test specimens using the steel coating prevention approach exhibit a higher degree of positivity in comparison to the prevention method including surface coating. The unprotected approach exhibits outcomes that lean towards being more unfavorable compared to the steel coating prevention method and the surface coating prevention method. The findings indicate that the performance of reinforcing steel embedded within a 3 cm mortar cover depth is often worse when compared to reinforcing steel situated inside a 5 cm mortar cover depth.

Abstract: Fly ash is a solid waste produced by power plants. To overcome the bad effects on the environment, fly ash is used as a substitute for cement in making concrete. Apart from that, the innovation of aggregate replacement materials in mixing concrete also has several alternatives, one of which is the use of sea sand as a substitute for fine aggregate. This research was conducted to determine the best proportion of sea sand use 10–40% with two treatments (washed and unwashed) and the use of fly ash of 20-30% on the corrosion resistance of reinforcing steel and the mechanical properties of concrete. The research results show that using up to 30% washed sea sand and 10% unwashed sea sand can increase compressive strength when compared to normal concrete. The use of up to 30% fly ash together with 20% sea sand has the same compressive strength as normal concrete. Apart from that, the use of sea sand and fly ash together has a low-risk category for reinforcing steel corrosion (10% risk of corrosion).

Abstract: Compressor valve spring failure and rapid fracture occurred in a petrochemical enterprise. To find the cause of the failure, and to ensure the safe, stable, and continuous operation of the device, the failure of the spring is analyzed. In this paper, through the macro inspection, chemical composition analysis, metallographic analysis, scanning electron microscopy analysis, energy spectrum analysis, hardness analysis, and other tests, it is concluded that the main reason for the spring fracture is the fatigue fracture caused by unqualified materials. Suggestions are given to avoid similar problems in the future, and it is hoped that this failure analysis will provide valuable experience for similar failure problems in petrochemical enterprises.

Abstract: To pinpoint the relationship between the microstructure and corrosion resistance of the B10 copper tube, the copper tubes were annealed at 780°C and 810°C, respectively. Then the simulated seawater full immersion experiment was conducted. The corrosion film, grain size, boundary characteristics, and intragranular microstructure of the alloy were analyzed by OM, SEM, EBSD, and TEM. The results implied that the corrosion rate of the 810°C annealed copper tube is about 0.028 mm/a, which is 1.9 times that of the 780°C annealed copper tube. The average grain size of 810°C annealed copper tube is about 38.85 μm and the low ΣCSL account for 64.8 %, which is 1.5 times and 1.4 times that of 780°C annealed copper tube, respectively. There is a complete spinodal decomposition structure within the grain in an 810°C annealed copper tube, but there is an incomplete spinodal decomposition structure in a 780°C annealed copper tube. Theoretical analysis indicated that the large-sized grain clusters could be formed by numerous low-layer fault energy twin boundaries Σ3, and low ΣCSL combination Σ3, Σ9, Σ27, which can block the large crystal boundaries network, inhibit the phase precipitation and prevent invading of corrosive elements along the large crystal boundaries. The intragranular spinodal decomposition structure can improve the strength and toughness of the B10 copper tube, reduce the initiation of surface microcracks during service, and thus reduce pitting and crevice corrosion.

Abstract: Ti-6Al-4V, renowned for its high strength and corrosion resistance, is a preferred material in aerospace and marine applications for lightweight structures due to its durability in challenging environments. Typically, GTAW welding is used for it’s fabrication. The residual tensile stresses produced after welding are known to worsen the corrosion and mechanical properties of welds. However, these properties can be improved by introducing near surface residual compressive stress by shot peening. When compared to the traditional shot peening treatment, the surface roughness that results from multiple shot peening with varying ball sizes and intensities can be significantly reduced. In the present work, Ti-6Al-4V plates were welded using conventional GTAW technique. Six different combinations of multiple shot peening treatments were applied to the welded specimens. Surface morphology and surface roughness were analysed. Surface residual stresses measurement were performed using by X-ray stress analyzer. Domain size and microstrain were measured using X-ray diffraction technique. Micro-hardness measurements were made along the weld thickness. Corrosion studies were carried out using potentiodynamic polarization test in 3.5% NaCl solution. The SP4 parameter comes out to have the best combination among all the multiple shot peened samples. It results in lowered surface roughness, higher compressive residual stress, better grain refinement, increased surface hardness, and enhanced corrosion resistance.

Abstract: Failure in manufacturing industries is a worldwide concern and it occurs most often at elevated temperatures and pressure. Acid, gases, and steam are known to be corrosion and stress-induced propagators resulting in incessant catastrophes. More so, material failure can be due to the substrate material used in the coating while substrate failure can further be classified into the substrate morphology, surface chemistry as well as contamination. Thus, the study developed a multifaceted layer of zinc barrier coating via the electrodeposition technique and observe its response by characterizing the developed coating. The mild steel plate, Zn and MnO₂ were procured and characterized according to the ASTM standard. Mild steel of dimension 60×30×2 mm was sectioned and polished using varying sizes of abrasives. The result of the coating thickness showed that Zn-6MnO₂ had a weight gain of 0.30g. Zn-12MnO₂ was observed to have excellent corrosion performance compared to the as-received and the other formulations of Zn-MnO₂ with a corrosion resistance of 2.117 mm/year. The SEM image of Zn-MnO₂ showed aggregates of clustered grains, thus, no possible fracture lines were observed on the coating surface. Zn-12MnO₂ exhibited a hardness value of 252.72 BHN. Additionally, the EDS of the coatings revealed significant elements that helped in the corrosion performance and hardness properties of the coatings. Keywords: Electrodeposition, Corrosion, Zinc barrier coating, Hardness value, EDS analysis

Abstract: This study investigated the impact from nitrogen content in backing gases on the microstructure and corrosion resistance of food grade stainless steel weld metal. Three types of backing gases were employed: 100%Ar, 85%Ar+15%N₂, and 100%N₂. Statistical analysis using ANOVA revealed a significant effect from nitrogen content on the ferrite phase fraction within the weld metal microstructures (p-value = 3.5E-05), indicating a reduction in the ferrite phase with increasing nitrogen content. Moreover, increasing nitrogen content positively shifted the pitting corrosion potential, indicating enhanced corrosion resistance. Optical microscopy confirmed lower pit density in samples with nitrogen backing gas as compared with samples with argon backing gas. These findings underscore the crucial role of nitrogen content in backing gases at influencing microstructure and corrosion resistance in stainless steel weld metal, with higher nitrogen levels correlated with improved corrosion resistance.

Abstract: Analysis of literature sources and empirical data indicate a variety and a large volume of experimental material, which often characterizes the uncertainty and contradiction of information regarding the effect of sulphur and manganese on the corrosion behaviour of steels obtained using traditional methods. This leads to the need to search for new, alternative methods for its effective analysis. The task of assessing and predicting the corrosion properties of structural steels is a key one in the general problem of managing the operational reliability of welded metal structures and equipment for the chemical, metallurgical, oil and gas, mining and other industries. The possibilities of its solution consist of using new information technologies, a component of which is intelligent means of information processing, such as artificial neural networks (ANN). The use of ANN makes it possible to create qualitatively new hardware and software that significantly expand the classes of emerging problems and increase the efficiency of analysis and forecasting. In the process of long-term operation of metal structures in many industrial industries, the metal is in direct contact with sulfur-containing agents at high temperatures. This leads to the saturation of the surface layer of the metal with sulfur with a concentration of up to 0.6%, which further makes it impossible to carry out repair and welding operations due to the formation of hot cracks. It was found that adding metallic manganese into the electrode coating in an amount of 20-25% significantly increases (4-5 times) the resistance against the formation of hot cracks. Sulfur content in the deposited metal has the opposite effect on the appearance of hot cracks. So, with a sulfur content of 0.042% and more, the resistance of the metal against the formation of hot cracks decreases sharply. It is shown that an increase in the content of metallic manganese in the electrode coating significantly reduces the content of dissolved sulfur in the deposited metal. Moreover, this tendency is typical for steels with different sulfur content in the surface layers and with different service life. For example, for steel with a service life of 20 years, the initial sulfur content in the surface layer of the metal (up to 1 mm) was about 0.52%. Adding metallic manganese in the coating of electrodes in an amount of 20-25% made it possible to reduce the sulfur content in the deposited metal to 0.03-0.045%, i.e. 12.6-17.3 times. In addition, the corrosion rate decreases with an increase in the content of metallic manganese in the electrode coating. The lowest corrosion rate for all steels involved in the research was established at 20-25% manganese content in the coating.