• Steel and Composite Structures
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• v.47 no.5
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• pp.615-631
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• 2023

Steel corrosion induces structural deterioration of concrete-filled steel tubes (CFSTs), and any potential extreme action on a corroded CFST would pose a severe threat. This paper presents a comprehensive investigation on the lateral impact behaviour of CFSTs suffering from localised pitting corrosion damage. A refined finite element analysis model is developed for the simulation of locally corroded CFSTs subjected to lateral impact loads, which takes into account the strain rate effects on concrete and steel materials as well as the random nature of corrosion pits, i.e., the distribution patterns and the geometric characteristics. Full-range nonlinear analysis on the lateral impact behaviour in terms of loading and deforming time-history relations, nonlinear material stresses, composite actions, and energy dissipations are presented for CFSTs with no corrosion, uniform corrosion and pitting corrosion, respectively. Localised pitting corrosion is found to pose a more severe deterioration on the lateral impact behaviour of CFSTs due to the plastic deformation concentration, the weakened confinement and the reduction in energy absorption capacity of the steel tube. An extended parametric study is then carried out to identify the influence of the key parameters on the lateral impact behaviour of CFSTs with localised pitting corrosion. Finally, simplified design methods considering the features of pitting corrosion are proposed to predict the dynamic flexural capacity of locally pitted CFSTs subjected to lateral impact loads, and reasonable accuracy is obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1281-1282
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• 2010

• Corrosion Science and Technology
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• v.13 no.3
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• pp.95-101
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• 2014

The pitting corrosion behaviors between the constituent phases in F53 super duplex stainless steel (SDSS) in acidified chloride environments were investigated using a critical pitting corrosion temperature test, a potentiodynamic anodic polarization test, and the microstructure analyses through a SEM-EDS and a SAM. As the solution annealing temperature decreased from $1150^{\circ}C$ to $1050^{\circ}C$, the ${\gamma}$-phase fraction increased whereas the ${\alpha}$-phase fraction decreased. The pitting potential and the critical pitting temperature increased with a decrease of solution annealing temperature, thereby increasing the resistance to pitting corrosion. The pitting corrosion of the SDSS was selectively initiated at the ${\alpha}$-phases because the PREN (pitting resistance equivalent number, PREN = %Cr+3.3%Mo+30%N) value of the ${\gamma}$-phase is much larger than that of the ${\alpha}$-phase, irrespective of the solution annealing temperature. The pitting corrosion was finally propagated from the ${\alpha}$-phase to the ${\gamma}$-phase. The decrease of solution annealing temperature enhanced the resistance to pitting corrosion greatly in acidified chloride environments due to a decrease of PREN difference between the ${\gamma}$-phase and the ${\alpha}$-phase, that is, a decrease of $PREN{\gamma}$ by dilution of N in ${\gamma}$-phase with an increase in the ${\gamma}$-phase volume fraction and an increase of $PREN{\alpha}$ by enrichment of Cr and Mo in the ${\alpha}$-phase with a decrease in the ${\alpha}$-phase volume fraction.

• Corrosion Science and Technology
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• v.2 no.1
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• pp.18-25
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• 2003

Effects of the precipitation of $\sigma$ phase on the metastable pitting as a precursor of stable pitting corrosion and also on the progress of stale pitting of the 25Cr-7Ni-3Mo-0.25N duplex stainless steel were investigated in chloride solution. Electrochemical potential and current noises of the alloy were measured in 10 % ferric chloride solution ($FeCl_3$) with zero resistance ammeter (ZRA), and then analyzed by power spectral density (PSD) and by corrosion admittance ($A_c$) spectrum. With aging at $850^{\circ}C$, the passive film of the alloy was found to get significantly unstable as represented by power spectral density (PSD) and a transition from metastable pitting state to stable one was observed. In the corrosion admittance spectrum, the number of negative $A_c$ corresponding to the state of localized corrosion increased with aging, suggesting that the precipitation of $\sigma$ phase considerably degraded the passive film by depleting Cr and Mo around it at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries, thereby leading to the initiation of the pitting corrosion. However, the Cr and Mo at $\alpha/\sigma$ or $\gamma/\sigma$ phase boundaries which were once depleted due to the precipitation of the $\sigma$ phase were partly replenished by the diffusion of Cr and Mo from the surrounding matrix with aging time longer. The initiation of pitting seems to be associated with the precipitation density of the $\sigma$ phase with an effective size needed to induce the sufficient depletion of Cr and Mo around it.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1289-1290
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• 2010

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.184-189
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• 2008

Inhibitive effects of chromate, phosphate, sulfate, and borate on chloride pitting corrosion of Al have been investigated using cyclic voltammetry. During the anodic oxide growth, the critical concentration of chloride for pit initiation decreased in the order: chromate > phosphate > sulfate > borate, and the maximum pitting current density increases in the reverse order: chromate < phosphate < sulfate < borate. The decreasing pitting current density was observed in the successive polarization cycles, which was attributed to the aging of Al oxides and field relaxation at oxide/solution interface.

• Corrosion Science and Technology
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• v.2 no.5
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• pp.247-251
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• 2003

The corrosion forms of automotive body panels are various. One of the representations is a corrosion pitting and its propagation on the lapped portion by galvanic corrosion. But it has been difficult in correlation analysis about the corrosion propagation rate and mechanism of pitting and the actual automotive body in field. This present study interprets experimentally the rust pitting occurrence mechanism on the lapped panels through experimental methods. And field car investigation was executed for correlation analysis with experimental results. This paper compares corrosion propagation rate by pitting on hot-dip galvannealed steel sheets with corrosion forms in the automotive field condition. The research fundamentals which make it possible to predict the pitting occurrence and propagation on the lapped panels in the actual vehicles are given.

• Corrosion Science and Technology
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• v.14 no.4
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• pp.184-189
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• 2015

In this study, the combined effect of chloride and thiosulfate ions and the effect of the ratio of the two ions on passivation in 304L, 316L, and the duplex stainless steels 2101 and 2205 are investigated using potentiostatic scratch tests. Cyclic polarization and the scratch tests were used to understand the role of anions on localized corrosion in these systems. It was found that the thiosulfate pitting began at a lower potential for 2101 than 304L in 0.6 M NaCl + 0.03 M $Na_2S_2O_3$ solution. The pit morphologies for 304L, 316L, and 2101 in an 0.6 M NaCl + 0.03 M $Na_2S_2O_3$ solution were very different from each other. The results indicate that the pitting switches from predominately thiosulfate pitting to chloride pitting at approximately 0.1 V.

• Journal of the Korean Electrochemical Society
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• v.10 no.3
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• pp.175-178
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• 2007

Pure iron, Fe-0.4, and 1.2 wt.%Cu alloys were examined by conducting the electrochemical techniques in the weakly alkaline solution, pH9, controlled by $Ca(OH)_2$, solution added with 0.02M NaCl. The $R_P$ measured from ac impedance, selected 10 kHz and 10mHz, in weakly alkaline solutions containing chloride ions indicated that the addition of copper up to 1.2wt.% into the pure iron significantly improved the pitting resistance of iron. In contrast to alloy, the pure iron showed the rapid pitting occurrences in drying period. During the drying period, the corrosion potential of pure iron was shifted to less noble value, pitting initiation.

• Corrosion Science and Technology
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• v.16 no.4
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• pp.167-174
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• 2017

Bicarbonate/carbonate and molybdate anions have been characterized for their inhibitive effect on pitting corrosion of carbon steel in simulated concrete pore solution by using electrochemical tests such as electrochemical impedance (EIS) and linear polarization (LP). It was revealed that bicarbonate/carbonate has a weak inhibitive effect on pitting corrosion that is approximately one order of magnitude lower compared to hydroxide. Molybdate is effective against pitting corrosion induced by the concentration of chloride as low as 113 mM and can increase the pitting potential of a previously pitted sample to the oxygen evolution potential by the concentration of molybdate as much as 14.6 mM only. The formation of a $CaMoO_4$ film on the surface hinders the reduction of dissolved oxygen on the steel surface, reducing corrosion potential and increasing the safety margin between corrosion potential and pitting potential further. In addition, pore-plugging by $FeMoO_4$ as a type of salt film within pits increases the likelihood of repassivation.