Corrosion Exposure Time Research Articles

Fire performance of aged and corroded reinforced concrete columns

The existing guidelines for determining the fire ratings of reinforced concrete (RC) columns only take into account undamaged components, without considering any deterioration caused by age or corrosion. An experimental study was conducted to examine the effect of corrosion on the fire performance of RC columns. In this study, six full-scale RC column specimens were cast, corroded, and tested in fire conditions, consisting of two made of normal strength concrete (NSC) and four made of high-strength concrete (HSC). Out of these six, three RC columns (1-NSC and 2-HSC) were corroded using a specifically designed accelerated corrosion setup for a target mass loss of 30 %. After the completion of the accelerated corrosion exposure time, these three corroded column specimens, along with three other non-corroded control column specimens, were tested in a fire furnace, simulating the ISO-834 fire curve. It was found that due to corrosion exposure, the steel reinforcement underwent significant mass loss, and severe corrosion cracks were observed. These cracks were discovered to serve as convenient channels for heat transfer. This facilitated the earlier and more severe spalling of the concrete cover, ultimately leading to premature deterioration in the strength of the corroded RC columns during the fire. Consequently, this contributed to the catastrophic failure of the corroded RC columns, with a significant reduction in fire ratings- 44 % for NSC columns and 40.49 % for HSC columns. This paper also addresses the spalling characteristics of the corroded columns and their structural responses, including axial deformations, lateral deformations, and load variations.

Investigation of Linear and Nonlinear Behaviour of Reinforced Concrete Column Exposed to Corrosion Effect for Different Damage Limit Levels

The high performance of reinforced concrete structural elements under the effects of lateral loads such as earthquakes is of great importance in terms of minimizing the loss of life and property that may occur due to earthquakes. One of the parameters affecting the earthquake behavior of a reinforced concrete structure is the corrosion effect. The aim of this study is to investigate the behavior of reinforced concrete columns exposed to different corrosion levels for different durations within the damage limits. In this direction, it is aimed to perform linear and nonlinear analysis of reinforced concrete columns in 5 different corrosion scenarios. In the study, nonlinear analyzes of the column were made using ANSYS software, the data obtained were determined for different damage limit levels and compared with the section analysis. Because of the study, moment-curvature relations, lateral load-horizontal displacement relations, bending ductility and plastic rotation capacity of the reinforced concrete column were determined for each corrosion scenario.

Cryo treatment and corrosion studies of nickel-titanium shape-memory alloy

Nickel (Ni)-titanium (Ti) shape-memory alloy (SMA) is a functional material that has received a higher demand in aerospace industries, biomedical industries, actuator, and sensor industries owing to the property of superelasticity and shape memory effect. In addition, SMAs offer better mechanical and corrosion-resistant properties. In this current work, cryo treatment of NiTi alloy has been carried out to investigate the change in the properties. NiTi SMA prepared by powder metallurgy are cryo treated for 12 hours to 48 hours. Further, a corrosion study has been performed on the cryo-treated NiTi samples with the variation in corrosion time to know the effect on the morphology and the hardness. It is found that cryo-treated NiTi shows higher resistance to corrosion than the non-treated sample. The present work is an attempt to find out the effect of cryo treatment on the hardness and corrosion behavior of NiTi SMA. In the scanning electron microscope (SEM) analysis, it is observed that with the increase in cryo treatment time, NiTi (martensite) phase increases. Similar phases are present in both untreated and cryo-treated NiTi pellets. Out of all cryo-treated NiTi pellets, 24 hours cryo-treated NiTi has a lower percentage of corroded area with an increase in the corrosion exposure time. Corrosion preferentially starts at the pit area and progresses toward the Ti-rich area. The hardness value increased for 48 hours cryo-treated sample when compared with other cryo-treated and untreated NiTi pellets.

Corrosion resistance of aluminum alloy 2198 for different ageing tempers

The present work investigates the influence of two different ageing tempers (T3 and T8) on the corrosion resistance of Al-Cu-Li (2198) aluminium alloy. Electrochemical impedance spectroscopy (EIS) measurements were employed in 3.5 wt. % NaCl solution to investigate the corrosion behaviour of the alloy. Additionally, the related equivalent circuit model was established to analyse the corrosion mechanism of this alloy. The EIS results showed two different corrosion mechanisms for the different exposure times in both tempers of the alloy; pitting corrosion – associated with attack of the surface oxide film - occurs between 1 h and 6 h of immersion while corrosion dissolution becomes severe after 12 h corrosion exposure time. The T8 temper showed lower corrosion resistance of the oxide film in the first stages of exposure, but corrosion attack seems to propagate in lower rates at this temper, when compared to the T3 temper.

Mechanical behavior associated with metallurgical aspects of friction stir welded Al–Li alloy exposed to exfoliation corrosion test

This research aims to investigate the effect of the exfoliation corrosion exposure time on the mechanical properties, the strength and elongation, of friction stir welded Al–Li alloy type 2195-T8. The exfoliation corrosion test was performed using the exfoliation corrosion (EXCO) solution, based on ASTM G34. The samples were exposed to different exposure times 24, 48, 96, 192 and 384 h. The results showed that both the strength and elongation of the welded specimens—exposed to the exfoliation corrosion tests—were reduced. For example, the samples that were exposed to 384 h, their initial tensile strength and elongation were reduced by 13% and 17% respectively. The degradation process due to the exfoliation corrosion on the tensile strength was divided into three stages: fast (0–96 h: 443.7 MPa-416.3 MPa, the degraded rate was 0.29 MPa/h), steady (96–192 h: 416.3 MPa-413.4 MPa, the degraded rate was 0.03 MPa h−1) and medium rate (192–384 h: 413.4 MPa-386.7 MPa, the degraded rate was 0.14 MPa h−1). For the elongation, in general, the reduction was similar to the style of strength, but with different rates. The TEM images showed that this degradation was due to the dissolution of T1 (Al2CuLi) and S′ (Al2CuMg) phase. Also, the corrosion products and their role of adherence on the surface of the tested specimens were investigated. An empirical equation p-t (mechanical properties-exposure time) was established to calculate the effect of exposure corrosion time on the performance of welded specimens.

Analysis of corrosion on sintered stainless steel: Mechanical and physical aspects

Abstract This research aims to examine the effects of a corrosive atmosphere on samples of 316 L sintered stainless steel. A salt spray test chamber was used to simulate cyclic exposure to a corrosive environment. The samples were deposited using different process parameter sets by selective laser melting. The energy density (Ev) was varied on three levels, and the effects of volume energy density on the weight, density, and corrosion resistance were investigated. Furthermore, weight and density measurements were carried out at the end of the accelerated corrosion tests. The morphology of the corrosion sample surfaces was characterized by means of scanning electron microscopy. The mechanical properties before and at the end of the accelerated corrosion were evaluated according to yield strength, tensile strength, and elongation at breakage. The experimental results demonstrate that both the weight and density increase when Ev is increased. The corrosion tests exhibited slightly different corrosion behaviors as a function of the Ev used. Samples deposited at the maximum energy generally exhibited less corrosion and the highest tensile properties owing to the low distribution of defects inside the sample. However, improved tensile properties continued to emerge following each exposure time interval in the corrosion process. It was found that the influence of the “exposure time interval” factor is non-existent for the ultimate tensile strength, yield stress, and strain at fracture, as these did not change with the accelerated corrosion exposure time.

Effect of laser ablation treatment on corrosion resistance of adhesive-bonded Al alloy joints

Laser ablation treatment modifies the chemical property (i.e. increased surface oxide layer) and topography (i.e. rough surface microstructures) of Al alloy substrates, and both aspects are considered as contributing factors to the corrosion resistance of adhesive-bonded joints. To analyze the effects of modified chemical property and topography on corrosion resistance of adhesive-bonded Al alloy joints, the laser ablation treatments were applied to Al alloy with/without argon shielding gas and in different power levels. Results show that although the increased surface oxide layer resulting from laser ablation treatment greatly improves the corrosion resistance of Al alloy substrate, it has negligible effect on corrosion resistance of adhesive-bonded Al alloy joints. Nevertheless, the modified surface topography has a significant effect on corrosion resistance of adhesive-bonded Al alloy joints. The bonding interfaces of joints fabricated from Al alloy substrates with relatively smooth surface topography are continuously broken by salt solution with the extension of corrosion exposure time, which changes the failure mode from cohesive to adhesive failure. The rough surface topography prevents the diffusion of salt solution through the Al/adhesive bonding interface and consequently protects Al alloy from being corroded, which results in better corrosion resistance of adhesive-bonded Al alloy joints.

Effect of corrosion exposure on the mechanical performance of 2024 aluminum alloy electron beam welded joints

The present work is focused on the effect of corrosion exposure on 2024-T3 electron beam welded joints. Sheets were face-to-face electron beam welded and tensile specimens were extracted from the sheets. The welded region was in the middle section of their gauge length. The specimens were exposed to exfoliation corrosion solution and for different exposure times to investigate the effect on the tensile mechanical properties. Non-corroded specimens showed that the joining efficiency of electron beam welded specimens is ~70%. Conventional yield stress decreased with corrosion exposure time, with small exposure times (<8 h) exhibiting a high corrosion-induced decrease rate. Corrosion-induced decrease of tensile elongation at fracture seems to follow an exponential correlation against corrosion exposure time. Fracture started always from the weld’s root and for small exposure times fracture occurred within the fusion zone.

Effect of corrosion exposure on aluminum alloy 2024 for different artificial ageing conditions

The present work investigates the corrosion behaviour of AA2024 in two different conditions, named T3 and Peak-Ageing (PA), respectively. Tensile specimens were artificially aged up to the PA condition, subsequently corroded for different exposure times to exfoliation corrosion solution and then they were immediately tensile tested. The corrosion exposure seems to essentially affect the mechanical behaviour of the specimens in T3 condition while this was not the case for the specimens in PA condition. After only 2 h corrosion exposure time, almost 23 % decrease in elongation at fracture for AA2024-T3 was noticed, while less than half of this decrease was evident in the PA condition for the same corrosion exposure. For higher exposure times (> 24 h), specimens at PA condition exhibited lower corrosion-induced decrease in tensile ductility, thus implying that surface deterioration mechanism change with artificial ageing of heat-treatable aluminium alloys.

Corrosion damage evolution of the aircraft aluminum alloy 2024 T3

Purpose – The purpose of this paper is to quantify the corrosion damage evolution that has occurred on the aircraft aluminum alloy 2024 after the exposure to Exfoliation Corrosion Test (EXCO) solution. Moreover, the effect of the evolving corrosion damage on the materials mechanical properties has been assessed. The relevance of the corrosion damage induced by the exposure to the laboratory EXCO for linking it to the damage developed after the exposure of the material on several outdoor corrosive environments or in service is discussed. Design/methodology/approach – To induce corrosion damage the EXCO has been used. For the quantification of corrosion damage the metallographic features considered have been pit depth, diameter, pitting density and pit shape. The effect of the evolving corrosion damage on the materials mechanical properties has been assessed by means of tensile tests on pre corroded specimens. Findings – The results have shown that corrosion damage starts from pitting and evolves to exfoliation, after the development of intergranular corrosion. This evolution is expressed by the increase of the depth of attack, as well as through the significant growth of the diameter of the damaged areas. The results of the tensile tests performed on pre corroded material made an appreciable decrease of the materials tensile properties evident. The decrease of the tensile ductility may become dramatic and increases on severity with increasing corrosion exposure time. SEM fractography revealed a quasi-cleavage zone beneath the depth of corrosion attack. Originality/value – The results underline the impact of corrosion damage on the mechanical behavior of the aluminum alloy 2024 T3 and demonstrate the need for further investigation of the corrosion effect on the structural integrity of the material. This work provides an experimental database concerning the quantification of corrosion damage evolution and the loss of material properties due to corrosion.

Effect of corrosion-induced hydrogen embrittlement and its degradation impact on tensile properties and fracture toughness of (Al-Cu-Mg) 2024 alloy

In the present work, the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA), Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits, trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition, while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.

Corrosion Behavior of Corroded Sn–3.0Ag–0.5Cu Solder Alloy

The thermal property of Sn–3.0Ag–0.5Cu solder alloy under different corrosion exposure time was investigated. Prior to thermal characterization, Sn–3.0Ag–0.5Cu solder alloy was immersed in 3.5wt. % NaCl solution at various exposure times. The thermal properties of Sn–3.0Ag–0.5Cu revealed that the total heat absorbed and heat of fusion of the samples show decreasing trends as corrosion became more severe. The pasty range and melting point of the samples were unaffected by the severity of corrosion. Microstructural and elemental characterization revealed the presence of tin oxides, namely, SnO and SnO2; Cu- and Ag-containing corrosion by-products adhered to the surface of the corroded samples. The surfaces of the samples investigated revealed the evolution of the morphology of the corrosion by-products from flakes to coral-like structures.

The effect of artificial ageing heat treatments on the corrosion-induced hydrogen embrittlement of 2024 (Al–Cu) aluminium alloy

This work is focused on the role of microstructure (S-type particles) that are precipitated in the aluminium matrix due to artificial ageing on the tensile ductility decrease of 2024 aluminium alloy when exposed to exfoliation corrosion solution. A common, extremely short corrosion exposure time was selected to corrode the already heat-treated specimens in different conditions, including under-, peak- and over-ageing so as to avoid pitting formation and to concentrate only to hydrogen embrittlement degradation. Corrosion-induced yield stress decrease was less sensitive to the change of microstructure. Corrosion-induced tensile ductility decrease was correlated with the precipitation of S-phase particles, showing that the specimens at the peak-ageing (S″ and S′ precipitates) and over-ageing (S precipitates) exhibited the lowest decrease (∼11% and ∼22%, respectively) due to corrosion exposure. The highest ductility decrease (∼26%) was noticed for the T3 condition (as received) that limited GPB zones were formed on the grain boundaries. Tensile ductility decrease was also ageing temperature sensitive, as the lowest temperature gave the least ductility decrease, thus giving proof of the role of the precipitates on the corrosion mechanism. The results were explained based on the hydrogen trapping at the interphases of the S-type precipitates.

Mechanical Behavior of Corroded Protruding Rebars From Unfinished Concrete Structures

In the current study, the effects of chloride-induced corrosion on B500c semi-embedded steel bars, both immersed in a salt-spray chamber and on protruding areas of existing structures, are evaluated in terms of mass loss and mechanical characteristics. Comparison of corrosion damage rates between bare and semi-embedded specimens at the early stages of the corrosion test, indicates that the bare steel bars present quite high mass losses, which however, over exposure time reach approximately similar rates to the ones presented by the semi-embedded steel bars. As far as mechanical characteristics are concerned, the mass loss of semi-embedded steel rebars, at the protruding site, is related to the strength and ductility properties drop. At the same time, while the corrosion exposure time is increasing in bare samples, a continuous-almost linear and proportional to the mass loss-reduction of the strength properties and the uniform elongation is observed. Finally, a worth referring point is the appearance of two Ludder areas on stress-strain diagrams of semi-embedded steel bars, a point that confirms the different corrosion mechanism of protruding areas in comparison to the bare or the wholly embedded ones.

The Atmospheric Corrosion of Carbon Steel and Cast Iron in the Environment of South Mosul

The carbon steel and cast iron are widely used metals in engineering and industrial applications. In this study, samples of carbon steel and cast iron chosen and distributed on six selected sites in the southregion of Mosul city in Iraq, Because these sites distinguished by the existence of natural emanations of hydrogen sulfide gas is produced and the existence of materials that cause metal corrosion like sulfates and chlorides. The corrosion measured by weight loss method according to the standard (ISO 9223:1992) and the higher rates registered in the sites that contain high emanations of hydrogen sulfide gas and sulfates and chlorides. In addition, it became obvious that there is a relationship between the corrosion exposure time and the corrosion rates which decreased by increasing of corrosion exposure time and continuous increasing in weight loss. The test continued for a complete year. Key words: carbon steel, cast iron, corrosion.

Accelerated corrosion exposure in ultra thin sheets of 2024 aircraft aluminium alloy for GLARE applications

The effect of corrosion exposure on ultra thin (t<0.4mm) 2024-T3 aluminium sheet thickness is investigated. Microstructural analysis showed that for low accelerated corrosion exposure times, no surface deterioration existed and hence corresponding mechanical properties degradation was assumed to be incited by hydrogen diffusion and subsequent embrittlement. Medium exposure times resulted in cross-section reduction due to formation of sub-surface corrosion products, while crevice corrosion was evident for higher exposure times. Tensile specimens were pre-corroded for single or double sides and then mechanically tested. Decrease in mechanical properties was noticed for both L and T sheet rolling directions, even after a few minutes exposure, with transverse rolling direction having higher degradation values for same exposure times. It was noticed that a single sided corroded specimen needs approximately double exposure time to reach the same ductility decrease of a double sided specimen. Quantitative tensile properties degradation results are discussed; the results were correlated to observed corrosion degradation mechanisms. The stepwise ductile-to-brittle transition of tensile fracture mechanism with increasing corrosion exposure time was denoted via analysis of the ‘un-corroded’ region of tensile fracture surface. Single sided specimens exhibited quasi-cleavage fracture surfaces at the region below protected surface to corrosion.

Experimental and theoretical studies of corrosion-induced mechanical properties degradation of aircraft 2024 aluminum alloy

In the present work, the influence of the corrosion exposure time on the mechanical properties degradation of the aluminum 2024-T3 alloy is studied. Tensile and fracture toughness mechanical tests had been carried out on pre-corroded specimens, exposed for different times to laboratory accelerated, exfoliation corrosion solution. The test results show that both the tensile mechanical properties as well as the fracture toughness exponentially decreased with increasing exposure time. A mechanical model has been devised to calculate the specimen’s remaining effective thickness after different corrosion exposure times. It has been shown that the decrease in the alloy’s fracture toughness is mainly associated with the thickness reduction degradation mechanism and a small reduction is attributed to hydrogen embrittlement. The hydrogen embrittlement degradation mechanism is saturated for exposure times up to 24 h. For higher exposure times, the prevailing degradation mechanism of alloy’s fracture toughness is the formation of corrosion-induced surface cracks and the resulting reduction of the effective thickness of the test specimen. An FE model has been developed for a fast calculation of the uncorroded alloy’s fracture toughness with good results. The model has also been exploited to predict the alloy’s fracture toughness degradation for the increasing exposure time to corrosive environment.

The fatigue life of thick-walled autofrettaged cylinders with closed ends: Rees, D.W.A. Fatigue Fract. Eng. Mater. Struct. 1991 14 (1), 51–68

In the present work, the effect of artificial ageing of AA2024-T3 on the tensile mechanical properties and fracture toughness degradation due to corrosion exposure will be investigated. Tensile and fracture toughness specimens were artificially aged to tempers that correspond to Under-Ageing (UA), Peak-Ageing (PA) and Over-Ageing (OA) conditions and then were subsequently exposed to exfoliation corrosion environment. The corrosion exposure time was selected to be the least possible according to the experimental work of Alexopoulos et al. (2016) so as to avoid the formation of large surface pits, trying to simulate the hydrogen embrittlement degradation only. The mechanical test results show that minimum corrosion-induced decrease in elongation at fracture was achieved for the peak-ageing condition, while maximum was noticed at the under-ageing and over-ageing conditions. Yield stress decrease due to corrosion is less sensitive to tempering; fracture toughness decrease was sensitive to ageing heat treatment thus proving that the S΄ particles play a significant role on the corrosion-induced degradation.