High Chloride Environments Research Articles

Atmospheric Corrosion Behavior of Ni-advanced Weathering Steels in High-chloride Environment: Effect of Ni on Corrosion Morphology

Atmospheric Corrosion Behavior of Ni-advanced Weathering Steels in High-chloride Environment: Effect of Ni on Corrosion Morphology

Influence of Starch Admixtures and Silver Colloids Stabilised with Starch Hydrolysates on the Course of Electrochemical Potential Difference of Reinforcing Steel in High-chloride Environment

The purpose of the conducted study was to verify whether the use of concrete admixtures with modified starches and starches modified with stabilised silver colloids affects the course of electrochemical potential difference, and hence corrosion, of reinforcing steel in a chloride environment. In the tests, cross-linked starches and products of acid hydrolysis of starch (dextrins) were used as admixtures. The 1-molar aqueous solution of sodium chloride was used as an aggressive environment. The tests consisted of measuring the potential difference generated in the reinforcement corrosion cell on the surface for a period of 60 days and then assessing the risk of corrosion. The effect of the addition of starch derivatives on the properties of cement paste was investigated through a one-way ANOVA analysis of variance followed by post hoc tests. The test results showed that the use of concrete admixtures with cross-linked starches positively affects the passivation of the steel. The likelihood of reinforcing steel corrosion when using distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate admixtures is less than 5%. The results obtained showed an improved effect on the passivation of reinforcing steel in cement composites. Additionally, concrete samples may have microbicidal properties.

Effect of coarse calcareous aggregates on corrosion of steel reinforcement in marine concretes

Finely ground limestone, perhaps as part cement replacement, has been shown to reduce concrete permeability and enhance strength. Whether this holds also for coarse limestone aggregates is of both practical and environmental interest, particularly the effect on corrosion of steel reinforcement. This is confirmed herein with exposure tests over 14 years for a range of concretes exposed to a high chloride environment. Importantly, these concretes also showed delayed initiation of reinforcement corrosion and lower long-term corrosion losses compared with similar concretes made with coarse igneous or siliceous aggregates. The observations are attributed to enhanced bonding between cement-hydration products and the limestone aggregate surfaces. These findings are important both for reducing environmental impacts and greenhouse gasses and for extending the durability of reinforced concrete structures.

SERS Nanosensor for the Detection of Ag(I) Ions under High-Chloride Environment: Breaking Chloride Masking Effect

SERS Nanosensor for the Detection of Ag(I) Ions under High-Chloride Environment: Breaking Chloride Masking Effect

Stir casting technology for fabrication of biodegradable magnesium metal matrix composites containing different percentages of hydroxyapatite reinforcement material for biomedical purposes

Due to the superior biocompatibility and strength of magnesium and its alloys compared to other metallic alloys, such as those used in orthopaedics as a bone-implant material, they have recently been considered a breakthrough material for biomedical applications. However, before tissues have fully adjusted to the high chloride environment and physiological pH range of the physiological system, pure magnesium might lose its mechanical integrity. Therefore, it is believed that the development of magnesium matrix composites is an approach to decrease corrosion rates and improve their mechanical properties that are similar to those of natural bone. They are not required to be taken out once the wound has entirely healed because they are biodegradable as well, which might reduce the need for additional surgeries in the future. The stir casting technique has been employed in this workto produce samples of magnesium-based biodegradable metal matrix composites, referred to as M2H (Magnesium & 2.0 wt% Hydroxyapatite powder) and M4H (Magnesium & 4.0 wt% Hydroxyapatite powder), with varying amounts of hydroxyapatite powder as a reinforcement material. In this worktensile test samples (M2H-T1,T2 & M4H-T1,T2) andcompression test samples (M2H-C1,C2,C3& M4H-C1,C2,C3,C4)along with microstructural and SEM test samples (M2H-MS & M4H-MS)were prepared and cut to a suitable shape and size in accordance with ASTM standards. This paper mainly focuses on the samples preparation for mechanical testing and SEM characterisation.

Physical and chemical chloride binding characteristics of the hydration products for phosphoaluminate cement

Phosphoaluminate cement (PAC) has the potential to prepare the anti-corrosive coatings for rebar due to with high compactness and resistance to chloride. Whereas, the reports of the binding type, its ratio and binding capacity of PAC for chloride ions are not found up to now. Thus, the chloride binding performance of PAC hydration products, as well as the binding isotherms and kinetic models, were investigated in this work. The experimental results showed that the binding capacity of the fully hydrated sample reached 21.03 mg/g in 0.56 mol/L NaCl solution. Up to 80 % of this total was non-water-soluble chloride, dominated by the chemical binding of calcium hydroaluminates (i.e., C(A,P)H10 and C2(A,P)H8). The water-soluble chloride at 20 ℃ accounted for only 20 % and was mainly adsorbed physically by Al(OH)3 and Fe(OH)3 gels. The whole chloride binding process of hydration products was well described using Freundlich isotherm and Elovich kinetic models. Its non-water-soluble bound chloride was more suitable for D-R isotherm and Elovich kinetic models, while the water-soluble bound chloride was more applicable to Freundlich isotherm and PSO kinetic models. These data will offer theoretical support for the rational use of PAC in constructions exposed to high chloride environments, such as the ocean.

Electrochemical Performance of Concrete Conductive Anode Paint Used as an Impressed Current Anode Material

The impressed current cathodic protection (ICCP) technique is a widely accepted technique to control corrosion of steel in reinforced concrete structures exposed to a high chloride environment. With the growing applicability of the technique, this research focused on developing a new anode material for the system. The author’s previous zinc-rich paint (ZRP) anode is further modified to improve its properties and its performance to be suitable for ICCP. The new concrete conductive anode paint (CAP) was evaluated for various concrete elements with varying steel: concrete ratios. Results showed that concrete CAP possesses excellent electrical conductivity as the anode for the ICCP system irrespective of specimen size. Compared with other available commercial anode paint materials and ZRP anode, concrete CAP is more promising as an ICCP anode material and satisfies the required polarization requirement. Polarization performance showed anode is capable to protect reinforced concrete structure with varied steel: concrete or steel: anode ratio. With an anode current density of 20 mA/m2, the service life was evaluated as 45 years.

Using sulphoaluminate cement and calcium sulfate to modify the physical–chemical properties of Portland cement mortar for mechanized construction

The mortars with Portland cement (PC), sulphoaluminate cement (CSA) and calcium sulfate (C S¯) have the potential to improve mechanized construction efficiency and apply in high chloride environments. To better understand the performance of the mortars, this work investigated the roles of sulphoaluminate cement replacing Portland cement ratio (CRPR) and calcium sulfate to sulphoaluminate cement ratio (CCR) on the physical–chemical properties of the PC-CSA-C S¯ system. Results show that the variation of CRPR or CCR affects the setting time, strength, water absorption and chloride diffusion of the mortars. In the hydration process, it is found that aluminate (C3A) in PC and ye’elimite (C4A3S¯) in CSA compete in the reaction with C S¯ to form ettringite (AFt), and this competition affects the hydration and pore structure of the cementitious system. The volume of pores over 20 nm increases with CRPR, but declines with CCR. Moreover, compared with pore structure, ettringite (AFt) content and the hydration degree of alite (C3S), monosulfoaluminate (AFm) content has better effect on blocking chloride diffusion.

Embrittlement failure of 51CrV4 leaf springs

High strength quenched and tempered alloys are used in the manufacture of leaf springs, and peening techniques are used to induce compressive residual stresses on the tension surface of the individual leaves to resist fatigue crack growth. However, the extent of such residual stresses is usually limited to around 0.1–0.2 mm deep. Their beneficial effect can therefore be negated by corrosion pitting, while high strength steels are known to also be susceptible to environmental embrittlement in high chloride environments. This case study deals with an interesting example of environmental embrittlement of multileaf springs reportedly made from 60Si2Mn steel, but actually manufactured from 51CrV4 steel. Multiple cracks initiated from corrosion pits and fatigue failures occurred within 6–9 months from service entry of the vehicles. The embrittlement was triggered by the disinfecting and cleaning regime that reflected the use of the trucks for conveying animal feed.

A Study of the Corrosion of Polymethyl Methacrylate Coated Rebar Using Glancing Angle X-Ray Absorption Near Edge Spectroscopy

Polymer coatings can be used to mitigate the corrosion of steel in high-chloride environments. Obtaining speciation information from thin corrosion layers can be important for understanding corrosion mechanisms, including polymer coating failure. This study outlines the effectiveness of collecting glancing angle x-ray absorption near edge spectroscopy (GA-XANES) spectra at the Fe K-edge to obtain chemical speciation information at the polymer/steel interface without removal of the polymer film. The depth of penetration of the incident x rays can be altered by changing the incidence angle, allowing for more fluorescence signal from corrosion products to be detected relative to the Fe metal fluorescence signal in GA-XANES spectra. This study demonstrates the use of GA-XANES to study thin layers of steel corrosion and obtain depth profile information of steel corrosion products beneath a polymethyl methacrylate polymer coating.

Inhibitor efficiency of migratory corrosion inhibitors to reduce corrosion in reinforced concrete exposed to high chloride environment

Chloride-induced corrosion of steel reinforcement is the most important cause of premature failure of reinforced concrete structures. Corrosion inhibitors have proven to be an effective method to reduce corrosion rate in terms of application and cost-effectiveness. Various types of inhibitors are present such as organo-functional silanes, Amino-alcohol and Surfactant & amine salts-based inhibitors. The inhibitor efficiency of six major commercial migratory corrosion inhibitors, for reinforced concrete available in UK, was investigated using electrochemical study and permeability measurements to determine the most efficient inhibitor to protect steel in concrete with high chloride environment. It is showed that these compounds are effective inhibitors for reinforced concrete structures. Out of the tested inhibitors, organo-functional based inhibitors showed the best inhibitor efficiency and barrier properties.

Time Scale of Chloride-Induced Corrosion on Circular Section RC Linked Accelerated Test to Natural Corrosion

The time scale in accelerated decay is essential for studying the durability of reinforced concrete (RC) structures exposed to the chloride corrosion environment. An accelerated corrosion test (ACT) was carried out on RC specimens were conducted under different chloride concentrations and applied voltages, with the information of steel measured. A novel prediction model of the complete corrosion process is proposed to evaluate the time correlation between accelerated decay and natural corrosion. The corrosion process of RC is divided into two stages: corrosion initial stage and corrosion stage of reinforcement. For the first stage, the coefficient of circular section members is presented. For the second stage, the accelerated factor of the test for the natural environment is proposed based on the Arrhenius-type and Faraday’s law. It is calculated by making regressions among some values of parameters, while moving to natural corrosion are extrapolating. The accelerating effect of applied voltages increases in the low-chloride environment, which is better than that in the high-chloride environment. This study provides calibration of the time scale for laboratory tests to analyze the performance of RC structures after corrosion.

The Role of Mo Addition in the Improvement of Corrosion Resistance of Weathering Steel Under a Wet-Dry Cyclic Condition

It is known that Mo improves corrosion resistance of weathering steels in atmospheric corrosion environments.1 Mo dissolves as MoO4 2- in neutral solutions. If MoO4 2- is adsorbed to the surface of rust particles, it is expected that Mo-containing rusts are selectively permeable to cations and inhibit the permeation of chloride ions into the steel matrix.2 However, there is little report on the role of Mo addition in the improvement of the corrosion resistance of weathering steels. In this study, solution chemistry of electrolytes permeating through rust layers of a Mo-added weathering steel was investigated. In addition, a model interface between Mo-containing rusts and the steel matrix was fabricated, and its corrosion behavior under a wet-dry cyclic corrosion test was observed. From the results obtained in this study, the beneficial effect of Mo on the corrosion resistance of weathering steels was discussed.Commercial-type weathering steel (WS: Fe-0.5Cr-0.3Cu-0.2Ni) and 0.5 mass% Mo-added weathering steel (Mo-WS: Fe-0.3Cu-0.5Mo) sheets were used in this study. All the steel sheets were polished up to 100–150 µm in thickness with SiC papers. We conducted a wet-dry cyclic corrosion test based on ISO 16539 Method A. The dew point was kept at 301 K. An electrolyte layer of 1.0 mm in thickness was formed every cycles using 0.18 M NaCl. In order to examine the solution chemistry of the electrolyte permeating through rust layers, a model specimen simulating a rust/steel interface was fabricated. The steel sheets were placed on a silica glass. A pH test paper or a filter paper was also placed between the steel sheet and the silica glass. Those were fixed by a masking tape and an epoxy resin. Using the specimen, we conducted the cyclic corrosion test to form rust layers. When a penetration hole through the steel sheet was formed by rust growth, the permeating electrolytes were trapped by the pH test paper or the filter paper. The pH of the electrolytes was evaluated by the color change of the pH test paper. The electrolytes absorbed in the filter paper was extracted to pure water, and Cl- concentration was measured by ion chromatography. In addition, we observed the corrosion behavior of the steel sheets in the model specimen simulating the rust/steel interface without pH test and filter papers. When a penetration hole through the steel sheet was formed under the wet-dry cyclic corrosion test, the steel sheet in the back side corroded by the permeating electrolytes. The corrosion behavior of the steel sheet in the back side can be regarded as that in the rust/steel interface.After 10–15cycles of the corrosion test, the penetration holes were observed from the back side of the model specimens with both WS and Mo-WS. In both cases, the pH of the electrolytes was about 1. The Cl- concentration for Mo-WS was approximately 1.0 M, one-third of that for WS. From the EDS analysis for the cross section of the rust/steel interface of Mo-WS, the signal of Mo was distributed in the whole rust layers. It is confirmed that Mo-containing rust layers suppressed the permeation of Cl- into the rust/steel interface. Black and brown rusts were observed from the WS sheet in the model specimen immediately after the penetration by rust growth. Raman spectroscopic analysis showed that the black rust was Fe3O4, and the brown rusts were β-FeOOH, which is often detected from rust layers formed in high chloride environments. In the case of Mo-WS, only black rusts (Fe3O4) were observed. This result also supported the inhibition of the Cl- permeation through Mo-containing rust layers. It is thought that the Mo addition suppressed the enrichment of Cl- and the formation of highly reducible β-FeOOH at the rust/steel interface, leading to the decrease in the corrosion rate. Reference: 1) H. E. Townsend, Corrosion, 57, 497(2001).2) N. Sato, in Passivity of Metals and Semiconductors, Proceedings of the Eighth International Symposium, M. B. Ives, J. L. Luo, and J. R. Rodda, Editors, P. 283, The Electrochemical Society, Pennington, NJ (2001).

Behavior of blends of CSA and Portland cements in high chloride environment

Calcium SulfoAluminate (CSA) cement has received increasing interest in recent years, mainly for its environmental aspects. However, few drawbacks such as its higher cost, compared to Ordinary Portland Cement (OPC), or the high carbonation rate, limits its application in reinforced concrete even when high early strengths are required.A technological solution could be combining CSA cement with non-corrosive reinforcements, widely used for structure exposed to marine environments. In order to evaluate the feasibility of this innovative solution even in high chlorides environments, blends of CSA clinker and limestone Portland cement were investigated in combination with seawater and varying the constituent proportions.The results show that sulfates play a key role in the equilibria between AFt/AFm influencing the Friedel's salt formation, thus the ability to bind chlorides. An optimal blend composition, able to improve the durability of concrete in marine environment, is suggested.

Structure of the rust layer of weathering steel in A high chloride environment: A detailed characterization via HRTEM, STEM-EDS, and FIB-SEM

The structure of rust layer and corrosion kinetics of weathering steel in a high chloride environment were investigated. Using a combination of HRTEM, STEM-EDS, and FIB-SEM, the rust was characterized as a three-layer structure: inner layer containing α-FeOOH nanograins, outer layer containing spindle- and rod-like α-FeOOH and rod- and fiber-like β-FeOOH, and outermost layer containing laminar γ-FeOOH. Moreover, Ni was enriched at steel-rust interface and Cr was in the inner layer. Additionally, the corrosion involved two stages: the early rapid corrosion stage and the late slow corrosion stage due to the formation of a large amount of α-FeOOH nanograins.

Optimization of machining parameters of super alloy 2205 by WC inserts

In this work the turning operation is performed on Super alloy 2205 and their material removal rate also known as MRR and surface roughness (Ra) characteristics are investigated. Uncoated tungsten carbide tool is used to machine the Super alloy 2205. The super alloy 2205 is widely used because of its high strength and is used in high chloride and marine environments because of its high corrosion resistance characteristics. The machining was done in CNC lathe as per Taguchi’s methodology. L9 Orthogonal arrays are used for parameter design and it is widely used for optimizing quality and performance of the manufacturing processes. The main purpose of this investigation is to obtain optimal process parameters in turning the Super alloy 2205 for increasing the MRR and simultaneously decreasing the surface roughness of the manufactured component. Speed of the spindle, Feed and Depth of Cut are the factors selected as input parameters and the Material Removal Rate (MRR) and Surface Roughness are considered as output responses. The results are analyzed using MINITAB 19 software to know the optimal process parameters suitable for machining the alloy. ANOVA is conducted on the results obtained to find the contribution of each machining parameter and to know the key factor which influences the material removal rate and surface roughness. Results indicated that DOC dominated the MRR while machining the super alloy and Surface Roughness was influenced Spindle Speed and Feed rate.

Effect of Imidazoline Inhibitor on the Rehabilitation of Reinforced Concrete with Electromigration Method.

Steel bars embedded in reinforced concrete are vulnerable to corrosion in high chloride environments. Bidirectional electromigration rehabilitation (BIEM) is a novel method to enhance the durability of reinforced concrete by extracting chloride out of concrete and introducing an inhibitor to the surface of the steel bar under the action of an electric field. During the migration process, a higher ionization capacity of the inhibitor with a symmetrical molecular structure was introduced. A new imidazoline inhibitor was, therefore, employed in this study due to its great ionization capacity. The effect of imidazoline and triethylenetetramine inhibitor on chloride migration, corrosion potential, and strength of concrete were explored. The research results showed that the effect of chloride extraction and electrochemical chloride extraction made no significant difference on the surface of the concrete, where chloride extraction efficiency was more than 70%, and the chloride extraction efficiency was more than 90% around the location of the steel. while a dry-wet cycle test, the potential of concrete increased by about 200 mV by mixing imidazoline inhibitor. The imidazoline inhibitor was found to be effective at facilitating chloride migration and ameliorating corrosion, meanwhile, it had a negligible impact on the concrete’s strength.

Study on the Flexural Performance of Hybrid-Reinforced Concrete Beams with a New Cathodic Protection System Subjected to Corrosion.

Steel corrosion is considered as the main factor for the insufficient durability of concrete structures, especially in the marine environment. In this paper, to further inhibit steel corrosion in a high chloride environment and take advantage of the dual-functional carbon fiber reinforced polymer (CFRP), the impressed current cathodic protection (ICCP) technique was applied to the hybrid-reinforced concrete beam with internally embedded CFRP bars and steel fiber reinforced polymer composite bar (SFCB) as the anode material while the steel bar was compelled to the cathode. The effect of the new ICCP system on the flexural performance of the hybrid-reinforced concrete beam subjected to corrosion was verified experimentally. First, the electricity-accelerated precorrosion test was performed for the steel bar in the hybrid-reinforced beams with a target corrosion ratio of 5%. Then, the dry–wet cycles corrosion was conducted and the ICCP system was activated simultaneously for the hybrid-reinforced concrete beam for 180 days. Finally, the three-point bending experiment was carried out for the hybrid-reinforced concrete beams. The steel bars were taken out from the concrete to quantitatively measure the corrosion ratio after flexural tests. Results showed that the further corrosion of steel bars could be inhibited effectively by the ICCP treatment with the CFRP bar and the SFCB as the anode. Additionally, the ICCP system showed an obvious effect on the flexural behavior of the hybrid-reinforced concrete beams: The crack load and ultimate load, as well as the stiffness, were enhanced notably compared with the beam without ICCP treatment. Compared with the SFCB anode, the ICCP system with the CFRP bar as the anode material was more effective for the hybrid-reinforced concrete beam to prevent the steel corrosion.

Passivity breakdown of 13Cr stainless steel under high chloride and CO2 environment

Herein, the effect of high chloride ion (Cl−) concentration on the corrosion behavior and passive film breakdown of 13Cr martensitic stainless steel under CO2 environment was demonstrated. The Cl− concentration was varied from 30 to 150 g/L and cyclic potentiodynamic polarization was conducted to investigate the influence of the Cl− concentration on the corrosion potential (Ecorr), passive breakdown potential (Epit), and repassivation potential (Erep). The results of the polarization curves revealed that 13Cr stainless steel is susceptible to pitting under high Cl− concentration. The passive breakdown potential and repassivation potential decreased with the increase of Cl− concentration. The semiconducting behavior of the passive film was investigated by Mott-Schottky analysis and the point defect model (PDM). It was observed that the iron cation vacancies and oxygen vacancies were continuously generated by autocatalytic reactions and the higher Cl− concentration resulted in higher vacancies in the passive film. Once the excess vacancies condensed at the metal/film interface, the passive film became locally detached from the metal, which led to the breakdown of the passive film.

The Impact of Zinc Coating Specifications on Corrosion Resistance аnd Durability of Steels

The article contains the findings on impact of zinc coating specifications on corrosion resistance and service life of steels of various chemical composition used often in modern industries. Characteristics such as type, class, chemical compound and thickness of zinc-based coatings are also addressed. Experiments were performed in which corrosion rate and useful life of zinc coatings in probable operating-like conditions — i.e., in environments of varying degrees of corrosive power (humid and high-chloride environments) were determined. It has been established which one of the environments is the most corrosive for steels depending on the zinc-based coatings’ specifications. Qualitative (visual) and quantitative (gravimetric) assessment of corrosion resistance and service life of chosen steels is presented. Optimal hot dip galvanized coating specifications were determined using statistical analysis.