Sacrificial Dissolution of Zinc Electroplated and Cold Galvanized Coated Steel in Saline and Soil Environments: A Comparison

To protect steel structures, zinc coatings are mostly used as a sacrificial barrier. This research aims to estimate the dissolution tendency of the electroplated and zinc-rich cold galvanized (ZRCG) coatings of a controlled thickness (35 ± 1 μm) applied via brush and dip coating methods on the mild steel. To assess the corrosion behavior of these coated samples in 3.5% NaCl and 10% NaCl containing soil solutions, open circuit potential (OCP), cyclic polarization (CP), and electrochemical impedance spectroscopy (EIS) tests were performed. The more negative OCP and appreciably large corrosion rate of the electroplated and ZRCG coated samples in 3.5% NaCl solution highlighted the preferential dissolution of Zn coatings. However, in saline soil solution, the relatively positive OCP (>−850 mV vs. Cu/CuSO4) and lower corrosion rate of the electroplated and ZRCG coatings compared to the uncoated steel sample indicated their incapacity to protect the steel substrate. The CP scans of the zinc electroplated samples showed a positive hysteresis loop after 24 h of exposure in 3.5% NaCl and saline soil solutions attributing to the localized dissolution of the coating. Similarly, the appreciable decrease in the charge transfer resistance of the electroplated samples after 24 h of exposure corresponded to their accelerated dissolution. Compared to the localized dissolution of the electroplated and brush-coated samples, the dip-coated ZRCG samples exhibited uniform dissolution during the extended exposure (500 h) salt spray test.

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Galvanic Corrosion Study between Tensile-Stressed and Non-Stressed Carbon Steels in Simulated Concrete Pore Solution

Metals ◽

10.3390/met12010098 ◽

2022 ◽

Vol 12 (1) ◽

pp. 98

Author(s):

Zheng Dong ◽

Chuanqing Fu ◽

Amir Poursaee

Keyword(s):

Charge Transfer ◽

Tensile Stress ◽

Electrochemical Impedance ◽

Pore Solution ◽

Charge Transfer Resistance ◽

Open Circuit ◽

Carbon Steels ◽

Cyclic Polarization ◽

Transfer Resistance ◽

Low Frequencies

The present study investigated the galvanic effect between tensile-stressed and non-stressed carbon steels, in addition to the influence of the tensile stress on the passivation and corrosion behavior of steel in a simulated concrete pore solution. Three different levels of tensile stress, ranging from elastic to plastic stress on the surface, were applied by adjusting the displacement of C-shape carbon steel rings. Different electrochemical measurements including the open circuit potential (OCP), the electrochemical impedance spectroscopy (EIS), the zero-resistance ammetry (ZRA), and the cyclic polarization were performed. Based on the results of EIS, the tensile stress degraded the resistance of the oxide film in moderate frequencies while enhancing the charge transfer resistance in low frequencies during passivation. As corrosion propagated, the stressed steel yielded a similar charge transfer resistance to or an even lower charge transfer resistance than the non-stressed steel, especially in the case of plastic tensile stress. The galvanic effect between the tensile-stressed and non-stressed steels increased the chloride threshold value of the tensile-stressed steel, although the susceptibility to pitting corrosion was exhibited after being corroded.

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Environmentally favorable magnesium phosphate anti-corrosive coating on carbon steel and protective mechanisms

Scientific Reports ◽

10.1038/s41598-020-79613-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Siyi Yin ◽

Haiyan Yang ◽

Yinghao Dong ◽

Chengju Qu ◽

Jinghui Liu ◽

...

Keyword(s):

Linear Polarization ◽

Electrochemical Impedance ◽

Salt Spray ◽

Steel Structures ◽

Polymer Coatings ◽

Carbon Steels ◽

Magnesium Phosphate ◽

Corrosion Monitoring ◽

Nacl Solution ◽

Transfer Resistance

AbstractPolymer coatings are commonly used to protect carbon steels from corrosion but they are susceptible to weathering and many of them have environmental concerns. Therefore, we studied the possibility of an environmentally favorable inorganic magnesium phosphate cement (MPC) coating for protecting mild steel. A formulation suitable for coating steel was developed by compositional modification [i.e., incremental replacement of dead-burned magnesia (MgO) with magnesium hydroxide (Mg(OH)2)] to a road-repair MPC. This modification yielded an acceptable working time and prevented pore formation at the coating-steel interface. Corrosion monitoring by linear polarization and electrochemical impedance spectroscopy for 14 days found that, the MPC coating substantially increased the linear polarization resistance (Rp) [e.g., day 1: (8.2 ± 1.7) × 103 (nadir value) vs. 495 ± 55 Ω cm−2] and charge transfer resistance (Rct) (e.g., day 1: 9.3 × 103 vs. 3.8 × 102 Ω cm−2). The coated steel underwent neutral sodium chloride (NaCl) salt spray for 2400 h without visible rusting. Immersion for 24 h in liquids simulating the pore fluid indicated that, passivation by the excess MgO in the coating was a major contributor to its anti-corrosive property. Tafel polarization in the liquids found that, corrosion current density (Icorr) followed the rank: 3.5% NaCl solution (6.0 µA cm−2) > 3.5% NaCl solution containing MgO (3.6 µA cm−2) > 3.5% NaCl solution containing fragmented MPC (1.7 µA cm−2), suggesting that a physical barrier effect and dissolved phosphate ions improved its protection. This study shows that, MPC coating is a promising durable and environmentally favorable anti-corrosive material for protecting steel structures in some applications.

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Effect of Ni Concentration on the Surface Morphology and Corrosion Behavior of Zn-Ni Alloy Coatings

Metals ◽

10.3390/met12010096 ◽

2022 ◽

Vol 12 (1) ◽

pp. 96

Author(s):

Ameeq Farooq ◽

Sohaib Ahmad ◽

Kotiba Hamad ◽

Kashif Mairaj Deen

Keyword(s):

Surface Morphology ◽

Coating Thickness ◽

Steel Substrate ◽

Salt Spray ◽

Research Work ◽

Alloy Coating ◽

Open Circuit ◽

Dissolution Behavior ◽

Cyclic Polarization ◽

Ni Alloy

This research work aims to develop electrodeposited Zn-Ni alloy coatings with controlled dissolution tendencies on a mild steel substrate. The varying Ni concentration in the electroplating bath, i.e., 10, 15, 20 and 25 g·L−1, affected the surface morphology and electrochemical properties of the deposited Zn-Ni alloy coatings. SEM and EDS analysis revealed the resulting variation in surface morphology and composition. The electrochemical behavior of different coatings was evaluated by measuring the open circuit potential and cyclic polarization trends in 3.5 wt.% NaCl solution. The degradation behavior of the electrodeposited Zn-Ni coatings was estimated by conducting a salt spray test for 96 h. The addition of Ni in the coating influenced the coating thickness and surface morphology of the coatings. The coating thickness decreased from 38.2 ± 0.5 μm to 20.7 ± 0.5 μm with the increase in Ni concentration. Relatively negative corrosion potential (<−1074 ± 10 mV) of the Zn-Ni alloy coatings compared to the steel substrate (−969 mV) indicated the sacrificial dissolution behavior of the Zn-rich coatings. On the other hand, compared to the pure Zn (26.12 mpy), ~4 times lower corrosion rate of the Zn-Ni coating (7.85 mpy) was observed by the addition of 25 g·L−1 Ni+2 in the bath solution. These results highlighted that the dissolution rate of the sacrificial Zn-Ni alloy coatings can effectively be tuned by the addition of Ni in the alloy coating during the electrodeposition process.

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Application of Electrochemical Techniques to Characterization of the Corrosion Behaviors of GW63 Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.571 ◽

2007 ◽

Vol 546-549 ◽

pp. 571-574

Author(s):

Xing Wu Guo ◽

Jian Wei Chang ◽

Shang Ming He ◽

Peng Huai Fu ◽

Wen Jiang Ding

Keyword(s):

Electrochemical Impedance ◽

Electrochemical Techniques ◽

Open Circuit ◽

Cyclic Polarization ◽

Time Curve ◽

Completely Monotonic ◽

Treatment Conditions ◽

Impedance Variation ◽

Corrosion Behaviors

The corrosion behavior of GW63 (Mg-6wt.%Gd-3wt.%Y-0.4wt.%Zr) alloys in 5% NaCl aqueous solution has been investigated by PARSTAT 2273 instrument. The Open Circuit Potential (ECORR) vs. time curve, cyclic polarization (Pitting Scans) curve and Electrochemical Impedance Spectroscopy (EIS) was measured for the GW63 alloys in as-cast and T6 heat treatment conditions. The EIS results indicated that the tendency of impedance variation for as-cast condition was monotonic decreasing, however, the tendency of variation for T6 condition was not completely monotonic but the total tendency was decreasing. The values of impedance of GW63 alloy at 0.1 Hz are about 103 ohm-cm2 for as-cast and T6 condition.

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Corrosion Resistance of Waterborne Epoxy Resin Coating Cross-Linked by Modified Tetrabutyl Titanate

Scanning ◽

10.1155/2020/1392385 ◽

2020 ◽

Vol 2020 ◽

pp. 1-9

Author(s):

Lingli Xu ◽

Zheng Chen ◽

Fei Huang ◽

Yinze Zuo ◽

Xingling Shi ◽

...

Keyword(s):

Corrosion Resistance ◽

Epoxy Resin ◽

Electrochemical Impedance ◽

Steel Substrate ◽

Salt Spray ◽

Tetrabutyl Titanate ◽

Cross Linking ◽

Cross Link ◽

Oh Groups ◽

Acrylic Epoxy

The development of waterborne coating is essentially important for environmental protection, and cross-linking agent is of great significance for ensuring corrosion resistance of the coating. In this work, tetrabutyl titanate was modified by ethylene glycol and tris(2-hydroxyethyl) amine and used for the solidification of waterborne acrylic-epoxy resin. Fourier-transform infrared spectroscopy (FTIR) analysis revealed that the agent reacted with OH groups first to cross-link the resin preliminarily, and then, when the amount of agent was further increased, the amino groups opened epoxide rings resulting in a secondary cross-link. Field emission scanning electron microscope (FESEM) observation and electrochemical impedance spectroscopy (EIS) test found that, when the cross-linking agent was used at 6%, the coating remains intact and kept an impedance of as high as 108Ωcm2 even after being immersed in NaCl solution for 30 days. Copper-accelerated acetic acid-salt spray (CASS) test confirmed that the coating containing 6% cross-linking agent provided the best protection for the carbon steel substrate.

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Cr3C2-NiCr Coating for the Protection of API Steel Corrosion in Concentrated Sodium Chloride Solution

Crystals ◽

10.3390/cryst10040249 ◽

2020 ◽

Vol 10 (4) ◽

pp. 249

Author(s):

El-Sayed M. Sherif ◽

Magdy M. El Rayes ◽

Hany S. Abdo

Keyword(s):

Corrosion Resistance ◽

Sodium Chloride ◽

Corrosion Rate ◽

Electrochemical Impedance ◽

Pipeline Steel ◽

Protective Layer ◽

Steel Corrosion ◽

Corrosion Current ◽

Cyclic Polarization ◽

Current Time

In the present work, a layer of 75%Cr3C2−25%NiCr with thickness of 260 ± 15 µm was coated onto the API-2H pipeline steel surface using high-velocity oxy-fuel deposition. The effect of 75%Cr3C2−25%NiCr coating on the corrosion of the API steel after 1 h, 24 h, and 48 h exposure in 4.0% sodium chloride solutions is reported. The corrosion tests were performed using potentiodynamic cyclic polarization, electrochemical impedance spectroscopy, and chronoamperometric current–time techniques along with scanning electron microscopy and energy-dispersive X-ray analyses. The curves of polarization indicated that the presence of the coating increases the corrosion resistance of the steel through decreasing its corrosion current and corrosion rate. Impedance data showed that all resistances recorded higher values for the coated API steel. Chronoamperometric current–time measurements confirmed that the coated API steel has lower absolute current values and thus lower corrosion rate. All results proved that the presence of 75%Cr3C2−25%NiCr coating enhances the corrosion resistance of the API steel via the formation of a protective layer of Cr and Ni oxides, which could lead to decreasing the corrosion rate.

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Effect of pyrite on the electrochemical behavior of chalcopyrite at different potentials in pH 1.8 H2SO4

Journal of Chemical Research ◽

10.1177/1747519819873516 ◽

2019 ◽

Vol 43 (11-12) ◽

pp. 493-502

Author(s):

Qingyou Liu ◽

Shuai Wang ◽

Miao Chen ◽

Yi Yang

Keyword(s):

Electrochemical Impedance ◽

Saturated Calomel Electrode ◽

Surface Characteristics ◽

Charge Transfer Resistance ◽

Open Circuit ◽

Electrochemical Dissolution ◽

Passive Region ◽

Transfer Resistance ◽

Electrochemical Behaviors ◽

Passive Resistance

Chalcopyrite is the most abundant, but also one of the most refractory, copper sources. One way to enhance chalcopyrite’s electrochemical dissolution is by mixing it with pyrite. To understand how and to what extent pyrite affects chalcopyrite’s electrochemical dissolution at different potentials, the electrochemical behaviors of chalcopyrite, pyrite, and chalcopyrite–pyrite couples in pH 1.8 H2SO4 were studied by potentiodynamic and electrochemical impedance spectroscopy. Potentiodynamic curves showed their different electrochemical reaction states and electrode surface characteristics. From open-circuit potential to 470 mV (vs saturated calomel electrode), chalcopyrite–pyrite was passivated with Cu1− xFe1− yS2 [Formula: see text]; from 470 to 580 mV, trans-passive dissolution occurred, and in the passive region, Cu1− xFe1− yS2 transformed into Cu1− x− zS2; from 580 to 700 mV was an active region; and a pseudo-passive region was formed with CuS when the potential was above 700 mV. The smaller charge transfer resistance and passive resistance, as well as the smaller inductive relaxation, revealed how and to what extent the coupled pyrite accelerated the electrochemical dissolution of chalcopyrite.

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Corrosion study of low carbon steel under simulated geological disposal environments for HLW in China

10.5194/egusphere-egu2020-6413 ◽

2020 ◽

Author(s):

Junhua Dong

Keyword(s):

Carbon Steel ◽

Corrosion Rate ◽

Dissolved Oxygen ◽

Open Circuit Potential ◽

Steel Substrate ◽

Low Carbon Steel ◽

Open Circuit ◽

Localized Corrosion ◽

Low Carbon ◽

Simulated Groundwater

In the multi-barrier system of HLW repository, overpack is the first barrier to isolate high-level radioactive nuclides from biosphere, and Low carbon steel has been considered to be a promising candidate material for manufacturing the oberpack due to its good mechanical performance and workability and weldability. However, during thousands of years of geological disposal, the corrosion resistance of low carbon steel and its corrosion evolution behavior are the first element that must be fully understood, because it determines the life cycle of the artificial barrier.Conventional&#160;studies had suggested that the corrosion of low carbon steel under the deep geological environment was driven by hydrogen evolution reaction (HER) based on that the dissolved oxygen was completely depleted during the long term disposal. However, the residual oxygen content is a critical factor to determine the corrosion mode of cathodic reduction reaction. Thermodynamics data indicated that the initial ferrous corrosion products formed in the deaerated bicarbonate solution can be chemically oxidized into ferric substance by the trace content of dissolved oxygen, and the accumulated FeOOH as a cathodic depolarizer significantly increased the open circuit potential and enhanced the corrosion rate of the low carbon steel. Moreover, chloride and sulfate in the simulated groundwater can reduce the increase of open circuit potential but it still promotes the corrosion of the low carbon steel. As the environments contained aggressive anions and high concentration of dissolved oxygen, low carbon steel was prone to suffer from the localized corrosion and the corrosion rate was obviously increased. By alloying with some contents of Ni and Cu, the corrosion rate of low alloy steel was decreased by an order of magnitude and it was less prone to suffer from the localized corrosion.Under the conditions of simulated groundwater with different content of GMZ bentonite&#65292;the bentonite colloidal particle layer attached to the surface of low carbon steel showed blocking effect on resisting oxygen diffusion to the steel substrate, which consequently decrease the further oxidation of ferrous to ferric substances and the corrosion rate of low carbon steel. However, the barrier performance of bentonite colloids would be deteriorated due to their coagulation caused by the ferrous ions dissolved from the steel substrate. High content of bentonite was beneficial to maintain and to prolong the stabilization of the barrier system. An equivalent circuit model which correlates with the interfacial structure between electrode substrate and rust and bentonite layer was proposed. The fitting results showed a very good match between the model and experimental data, and the evolution of the results was also in agreement with real changes.

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Electrochemical Investigation of Corrosion of X80 Steel under Elastic and Plastic Tensile Stress in CO2 Environment

Metals ◽

10.3390/met8110949 ◽

2018 ◽

Vol 8 (11) ◽

pp. 949 ◽

Cited By ~ 2

Author(s):

Wei Wu ◽

Hailong Yin ◽

Hao Zhang ◽

Jia Kang ◽

Yun Li ◽

...

Keyword(s):

Corrosion Rate ◽

Tensile Stress ◽

Corrosion Behavior ◽

Electrochemical Impedance ◽

Pipeline Steel ◽

Open Circuit ◽

Co2 Corrosion ◽

X80 Pipeline Steel ◽

X80 Steel ◽

Co2 Environment

An investigation into the electrochemical corrosion behavior of X80 pipeline steel under different elastic and plastic tensile stress in a CO2-saturated NaCl solution has been carried out by using open-circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analysis techniques. The results show that the corrosion rate of X80 steel first increases and then slightly decreases with the increase of elastic tensile stress, whereas the corrosion rate sharply increases with the increase of plastic tensile stress. Both elastic and plastic tensile stress can enhance steel corrosion by improving the electrochemical activity of both anodic and cathodic reactions. Moreover, compared with elastic tensile stress, plastic tensile stress has a more significant effect. Furthermore, electrochemical reactions for CO2 corrosion and mechanoelectrochemical effect are used to reasonably explain the corrosion behavior of stressed X80 steel in CO2 environment.

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Multi-Leg TiO2 Nanotube Photoelectrodes Modified by Platinized Cyanographene with Enhanced Photoelectrochemical Performance

Catalysts ◽

10.3390/catal10060717 ◽

2020 ◽

Vol 10 (6) ◽

pp. 717 ◽

Cited By ~ 2

Author(s):

Mahdi Shahrezaei ◽

Seyyed Mohammad Hossein Hejazi ◽

Yalavarthi Rambabu ◽

Miroslav Vavrecka ◽

Aristides Bakandritsos ◽

...

Keyword(s):

Charge Transfer ◽

Recombination Rate ◽

Electrochemical Impedance ◽

Charge Transfer Resistance ◽

Open Circuit ◽

Transfer Time ◽

Photoelectrochemical Performance ◽

Transfer Resistance ◽

Photocurrent Spectroscopy ◽

Photogenerated Electrons

Highly ordered multi-leg TiO2 nanotubes (MLTNTs) functionalized with platinized cyanographene are proposed as a hybrid photoelectrode for enhanced photoelectrochemical water splitting. The platinized cyanographene and cyanographene/MLTNTs composite yielded photocurrent densities 1.66 and 1.25 times higher than those of the pristine MLTNTs nanotubes, respectively. Open circuit VOC decay (VOCD), electrochemical impedance spectroscopy (EIS), and intensity-modulated photocurrent spectroscopy (IMPS) analyses were performed to study the recombination rate, charge transfer characteristics, and transfer time of photogenerated electrons, respectively. According to the VOCD and IMPS results, the addition of (platinized) cynographene decreased the recombination rate and the transfer time of photogenerated electrons by one order of magnitude. Furthermore, EIS results showed that the (platinized) cyanographene MLTNTs composite has the lowest charge transfer resistance and therefore the highest photoelectrochemical performance.

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