Corrosion Resistance Of Carbon Steel Research Articles

Research on Aluminizing Process of Friction Coating and Its Corrosion Resistance

In this paper, a friction coating aluminizing process is used to create an aluminum coating layer on the surface of the steel, and a low-temperature diffusion treatment forms a Fe-Al infiltration layer to improve the corrosion resistance of carbon steel. This paper introduces the basic concepts, classifications, and application areas of aluminized steel, analyzes the corrosion mechanisms of aluminized steel in different environments and summarizes the commonly used evaluation methods. This paper also determined the appropriate range of parameters for the friction coating aluminizing process and investigated the effects of various process parameters on the surface structure and properties of the steel. Finally, this paper evaluates the corrosion resistance of friction-coating aluminized steel in typical environments. The results show that friction-coating aluminized steel has better corrosion resistance and can effectively prolong the service life of carbon steel.

Understanding of low-carbon steel marine corrosion through simulation in artificial seawater

<abstract> <p>The current laboratory experiments investigated the corrosion resistance of carbon steel in artificial seawater (ASW) using the steel coupons hanging on a closed glass reactor of ASW with volume-to-specimen area ratios ranging from 0.20 to 0.40 mL/mm<sup>2</sup>. These coupons were immersed in ASW for varying time durations (7 and 14 d) at room temperature without agitation. Further, the corrosion rates based on the weight loss and electrochemical analytical method were determined. Following exposure to carbon steel for 7 and 14 d, corrosion rates were 0.2780 <italic>mmpy</italic> and 0.3092 <italic>mmpy</italic>, respectively. The surfaces appeared to be not protected by oxides based on this result. The electrochemical impedance spectrometer in potentiostatic/galvanostatic mode, in conjunction with EDX analysis, predicted the evolution of oxygen reduction. The 7th-day immersion sample had a higher oxygen content, and the 14th-day immersion sample had a slightly lower oxygen content. Methods of X-ray diffraction (XRD) and scanning electron microscopy (SEM) characterized the surface morphology and composition of their corrosion product. Corrosion products derived from rust minerals hematite, lepidocrocite and magnetite appeared to cover the carbon steel surface after exposure. This result can get insight into the corrosion behavior of low-carbon steel used in marine environments.</p> </abstract>

Enhancing Corrosion Resistance of Carbon Steel in Sulfuric Acid Using β-cyclodextrin as an Inhibitor

The corrosion process leads to substantial economic losses, particularly in the industrial sector, emphasizing the importance of preventive measures. This study aimed to investigate the impact of inhibitor concentration, immersion duration, and temperature on the corrosion of carbon steel in a sulfuric acid environment, assessed through mass loss measurements. Inhibition efficiency displayed a positive correlation with increasing inhibitor concentration, while it declined as temperatures rose. In a 0.5 M sulfuric acid solution, β-cyclodextrin (β-CD) exhibited an inhibition efficiency of 62.26% at a concentration of 1 mM. The addition of potassium iodide (KI) significantly enhanced the inhibition efficiency to 97.98%, indicating a synergistic effect. The study encompassed various calculations, including the determination of activation energy (Ea), activation enthalpy (ΔHa), activation entropy (ΔSa), adsorption-free energy (ΔGads), adsorption enthalpy (ΔHads), and adsorption entropy (ΔSads). The adsorption of the inhibitor onto the carbon steel surface conformed to the Langmuir adsorption isotherm. Additionally, Scanning Electron Microscopy (SEM) investigations provided further verification of β-cyclodextrin's adsorption on the carbon steel surface.

Corrosion inhibitors for carbon steel: A review

AbstractCorrosion inhibitors are one of the practical and cost‐effective way of preventing and inhibiting corrosion. An inhibitor's primary function includes creating a barrier by forming one or more molecular layers to protect against corrosive attacks. Organic molecules are one of the most popular, efficient, and practical corrosion inhibitors, and all studies demonstrate that organic compounds, preferentially those containing nitrogen (N), sulphur (S), and oxygen (O), have high inhibitory efficiency. Also, corrosion inhibitors include inorganic compounds. Since inorganic and organic inhibitors are both toxic and expensive; emphasis is being placed on developing green corrosion inhibitors as well as on modification of inhibitors. We are focusing on carbon steel (CS) substrate in this review as it is the first‐line material and is widely employed in various industrial applications. Whereas corrosion resistance of CSs in acidic environments is a constantly evolving topic, working on better performance of CSs as more cost‐effective alternatives to other alloys.

Effect of quenching in aqueous polyvinylpyrrolidone solutions on the microstructure and pitting corrosion resistance of AISI 1045 carbon steel

AbstractCarbon steels are widely used as infrastructure components owing to their high strength, ductility, and weldability. However, as corrosion degrades critical infrastructure components, exploring the relationship between the microstructure and corrosion resistance of carbon steel is of particular interest in engineering. To analyze this relationship, it is first essential to evaluate the corrosion resistance of each microstructure in a carbon steel specimen with a single chemical composition to eliminate the effects of alloying elements. In this study, we compared the pitting corrosion resistance of four microstructures (water‐quenched martensite, tempered martensite, bainite and degenerate pearlite, and ferrite–pearlite) of an AISI 1045 medium‐carbon steel. The pitting corrosion resistances of the microstructures in near‐neutral pH solutions containing NaCl were ordered as follows: (high) water‐quenched martensite > bainite and degenerate pearlite > tempered martensite > ferrite–pearlite (low). Elucidating the effect of the microstructure on the pitting corrosion resistance may contribute to the development of corrosion‐resistant carbon steels with excellent mechanical properties.

Preparation of Phosphate Coating Solution to Increase the Corrosion Resistance of Carbon Steel in Ambient Conditions

In this work, different zinc phosphating solutions were prepared using sodium phosphate (Na3PO4), sodium nitrate (NaNO3), and nickel carbonate (NiCO3) as accelerators. NaNO3 concentration was ranged from 20 to 80 g/L. While the NiCO3 concentration ranged from 1 to 15 g/L. To identify the interactions between the NaNO3and NiCO3, mixed accelerators were also investigated. Corrosion inspection of the metal surface was tested using potentiostatic experiments. Portable camera microscope was used to capture the surface images of coated samples. The experimental investigations revealed that the immersion time of 10 min significantly enhanced the corrosion tendency of all accelerators. It was noticed that the corrosion resistance was enhanced with more concentration of NaNO3in the phosphate solution and reached their maximum protection at 80 g/L. While 1 g/L of NiCO3 in solution (which represents the lower value), exhibited higher protection against corrosion. Mixed accelerators resulted in smaller grain size with lower corrosion current (1.83 mA) at 80 g/L and 5 g/L of NaNO3 and NiCO3, respectively. It was also found that chromic acid concentration significantly affected the corrosion resistance.

Insights into the enhanced corrosion resistance of carbon steel in a novel low-carbon concrete with red mud and phytic acid

As a supplementary cementitious material, red mud (RM) has a great potential for producing low-carbon concrete. However, it may induce alkali-aggregate reaction owing to its high alkalinity, so acids have been widely used for neutralization. Moreover, as an organic corrosion inhibitor for metals used in acid and neutral environments, phytic acid (PA) is not suitable for direct application in reinforced concrete. Accordingly, a novel low-carbon and corrosion-resistant concrete was designed with both RM and PA. Due to the generation of a bilayer PA-related protective film on the steel surface, a synergistic inhibition mechanism of RM and PA was proposed.

The role of Cr content on the corrosion resistance of carbon steel and low-Cr steels in the CO2-saturated brine

The selection of appropriate materials for the transportation pipelines is of vital importance to ensure the safety operation in Carbon Capture, Utilisation and Storage (CCUS). To clarify the effects of Cr content in steel on the resistance against general and localised corrosion, electrochemistry methods combined with pH measurements and various surface analysis techniques were implemented on X65, 1Cr, 3Cr and 5Cr steel samples in a CO2-saturated solution at 60 °C and pH 6.6 during 192 h of immersion. Additionally, thermodynamic and kinetic analyses of the formation of the corrosion products on carbon steel and low-Cr steels were performed. The results show that the general corrosion resistance increased with rising Cr content without the presence of significant corrosion products formation. However, with the formation and development of the corrosion products, the general corrosion resistance reduced with the increase in Cr content. The formation of the compact crystalline FeCO3 on X65 and 1Cr steel surfaces offered superior general corrosion protection, while cannot provide enough localised corrosion protection. By contrast, the double-structural corrosion product layers on 3Cr and 5Cr steels notably suppressed the localised corrosion, but providing poor protection against general corrosion over long immersion periods. This study reveals the contributions of Cr content on general and localised corrosion resistance at various periods, providing references for material selection and evaluation in CO2 environments relevant for CCUS.

(Corrosion Division Morris Cohen Graduate Student Award) Microscopic Electrochemical Properties of Carbon Steels and Metallurgical Approach for High Corrosion Resistance

Carbon steels are widely used in the production of automobiles, bridges, plates, and so on because of their superior mechanical properties and low cost. Carbon steels contain various types of microstructures such as ferrite, pearlite, and martensite, and desired mechanical properties can be obtained by combining these microstructures. While carbon steels exhibit excellent mechanical properties, their pitting corrosion resistance is relatively low in chloride-containing environments. Although the steels are successfully protected from corrosion by coating and/or painting, localized corrosion is readily initiated at cut edges and in coating defect areas in atmospheric environments. To prolong their service life and improve their reliability, it is necessary to elucidate the initiation mechanism of pitting corrosion on carbon steels. While it is widely known that the microstructures of carbon steels affect their corrosion resistance, the detailed mechanism is still unclear. The objective of this research is to clarify the relationship between the microstructure and pitting corrosion resistance of carbon steels in chloride-containing near-neutral pH environments.The pitting corrosion resistance of the typical microstructures of carbon steels was investigated using a micro-electrochemical polarization technique. Various microstructures (ferrite, pearlite, tempered martensite, decarburized martensite, as-quenched martensite etc.) were obtained by conducting different heat-treatments, and micro-scale electrodes (ca. 100 μm × 100 μm) were prepared with only one microstructure included. Small areas without any non-metallic inclusions were chosen as the micro-scale electrodes to eliminate the effect of pit initiation at the inclusion and evaluate the intrinsic corrosion behavior of the microstructure itself. Then, potentiodynamic anodic polarization measurements were carried out in NaCl-containing boric-borate buffers at pH 8.0. It was determined that the pitting corrosion resistance depends on the type of microstructure, with the as-quenched martensite showing the highest pitting corrosion resistance. The as-quenched martensite includes a high amount of interstitial C in the Fe lattice, and it was also clarified that the anodic dissolution of steels was clearly suppressed with increasing interstitial C content. During pitting corrosion, the local breakdown of the passive film is induced by chloride ions, which results in the initiation of active dissolution. It was considered that the low dissolution rate provided by interstitial C results in the superior pitting corrosion resistance of as-quenched martensite.To clarify the reason for the superior active dissolution resistance obtained by interstitial C, first-principles calculations were conducted. At first, the electronic structure of martensite was analyzed using bulk-model supercells with bct Fe crystal structures which included interstitial C. According to first-principles calculations, the electronic density of states (DOS) at and around the Fermi level decreased due to the presence of interstitial C. In addition, a valence electron transfer occurred from Fe to C atoms, resulting in a decrease in the number of valence electrons of Fe. Because the presence of valence electrons at and around the Fermi level affects the kinetics of electron (charge) transfer in oxidation/reduction reactions, including the active dissolution reaction, it was considered possible that the presence of interstitial C suppressed the electronic reactivity of Fe. Furthermore, first-principles calculations were also carried out for slab-model supercells consisting of a metal/vacuum interface, and the effect of interstitial C on the work function of martensite was analyzed. The result of the calculations indicated the work function of martensite linearly increased with increasing interstitial C content. Since the work function and ionization energy of metals are the same, the electrochemical properties of metals, such as dissolution resistance, are considered to be principally associated with their work function. In other words, it is understood that metals with a high work function are associated with a higher dissolution resistance. According to the above calculation results, the change in the electronic structure of Fe and the increase in the work function provided by interstitial C are key factors contributing to the superior dissolution resistance of martensite.

Improved corrosion resistance of carbon steel in soft water with dendritic-polymer corrosion inhibitors

Dendritic polymers with an isothiourea terminal group, carboxyl lateral group, and pentitol core dendrimers with 0 and 1 generations (ITCP-0G and ITCP-1G) were developed as novel phosphorus-free corrosion inhibitors for carbon steel in soft water. The results of weight loss, Tafel polarization, and electrochemical impedance spectroscopy analyses showed that the corrosion inhibition performance of ITCP-0G and ITCP-1G of carbon steel in soft water was much higher than that of the previously reported corrosion inhibitors, whereas the performance of ITCP-1G is superior to that of ITCP-0G. An ITCP-1G concentration of 15 mg⋅L−1 achieved a corrosion inhibition efficiency of 97.62 %, which is higher than the value of 75.19 % achieved by ITCP-0G. The Langmuir adsorption isotherm model indicated spontaneous adsorption of ITCP-1G on the carbon steel surface. Comprehensive surface analysis indicated that S and N in the terminal isothiourea of ITCP molecules bind with iron to form a protective film on the steel surface. Increasing the number of terminal isothiourea groups in the dendrimers results in a stronger binding force with Fe ions, and a stronger protective film is formed on the steel surface. Additionally, larger dendrimer molecules provide better surface coverage of the protective film on the steel surface and better corrosion inhibition performance. Therefore, ITCP-1G had a stronger ability to prevent the anodic corrosion of iron from carbon steel than ITCP-0G. This work will provide new insights into the corrosion inhibition mechanism of corrosion inhibitors in soft water as well as the development of new types of water-softening corrosion inhibitors.

Study on Corrosion Resistance of Carbon Steel in HF/HCl Acid Mixture in Presence of Lycoris radiata and Lycoris chinensis Leaf Extract as Environmentally Friendly Corrosion Inhibitor

Study on Corrosion Resistance of Carbon Steel in HF/HCl Acid Mixture in Presence of Lycoris radiata and Lycoris chinensis Leaf Extract as Environmentally Friendly Corrosion Inhibitor

Corrosion resistance of carbon steel in alkaline concrete pore solutions containing phytate and chloride ions

The influence of phytate ions (IP6) on the corrosion resistance of carbon steel with and without passive films in simulated concrete pore solutions with chloride ions was investigated using various electrochemical measurements and surface characterization techniques. The results show that IP6 can effectively improve the corrosion resistance of the bare carbon steel. However, IP6 is confirmed to be detrimental to the naturally formed passive films, thus decreasing the corrosion resistance of the pre-passivated carbon steel. Moreover, owing to the synergistic degradation effects of IP6 and chloride ions, the more pronounced pitting corrosion is highlighted for the pre-passivated carbon steel.

An environmentally friendly formulation based on Cannabis sativa L. seed oil for corrosion inhibition of E24 steel in HCl medium: Experimental and theoretical study

The poor corrosion resistance of carbon steel (CS) has long been an urgent challenge to its industrial applications. Green corrosion inhibitors are among the most widely used and economically viable methods to protect metals and alloys against corrosion. In the present work, a new green corrosion inhibitor formulation (CIF) based on Cannabis sativa L. seed oil (noted CSL) was prepared for protecting E24 carbon steel against corrosion in 1.0 mol/L HCl. Experiments were carried out using weight loss (WL), and electrochemical methods at different concentrations of CSL and immersion times. The surface morphology of corroded and inhibited CS was investigated using the scanning electron microscope (SEM), while Density Functional Theory (DFT) and molecular dynamics (MD) simulation were used to assess the reactivity of CSL’s components and their interactions with Fe(110) plane. The gas chromatographic analysis of the CSL indicated that the Linoleic acid (C18:2) is the most abundant fatty acid (51.3%), followed by Oleic acid ((C18:1) (20.3%)), α-Linolenic acid (C18:3 (15.7%)) and saturated Palmitic acid (C16:0 (7.9%)). According to WL and electrochemical results, an inhibition efficiency of over 92% was achieved using 1 g/L of CSL, indicating higher corrosion mitigation properties. Electrochemical results revealed that the tested formulation had a mixed-type inhibition effect, with a cathodic predominance. In addition, the charge transfer resistance of the CS electrode increased from 46 Ω cm2 in blank solution to 1115 Ω cm2 in HCl solution inhibited with 1 g/L of CSL and 24 h immersion. SEM images showed the formation of a protective barrier on CS surface, which prevented the corrosion attack. DFT and MD studies showed that CSL’s components have excellent donor-acceptor properties and exhibited a close contact with Fe(110) surface upon adsorption.

Thermodynamic Analysis and Crystallographic Properties of MFe2O4, MCr2O4 and MAl2O4 (M = Fe, Ni, Zn) Formed on Structural Materials in Pressurized Water Reactor Primary Circuit under Zinc and Zinc-aluminum Water Chemistry.

Zinc injection technology (zinc water chemistry, ZWC) was widely applied in pressurized water reactor (PWR) primary circuits to reduce radiation buildup and improve corrosion resistance of structural materials. The simultaneous injection of zinc-aluminium (ZAWC) is a novel implement created to replace part of Zn2+ by Al3+. It was reported ZAWC can improve further corrosion resistance of carbon steels and stainless steels. However, ZAWC sometimes showed even negative effects on Nickel-alloys. In this study, mechanism of formation of oxide film on metals was investigated. The reactions of Fe2+ Ni2+ in oxide films replaced by Zn2+, or Fe3+ replaced by Al3+ in ZAWC were analysed. The thermodynamic data and solubility of mixed oxides (ZnFe2O4, ZnCr2O4, and ZnAl2O4), the products of replace reactions, were calculated. According to the Gibbs free energy difference between products and reactants, values of the formation reaction of ZnFe2O4, ZnCr2O4, and ZnAl2O4 are extremely negative. Solubility of ZnAl2O4 is the lowest among mixed oxide products, which implies the oxide film composites of ZnAl2O4 may show a lower corrosion rate. In addition, the preferential formation of NiAl2O4 on Ni-based-alloy, under ZAWC, was discussed based on crystallographic properties of spinel, which was considered as the cause of negative effects of ZAWC on corrosion resistance of Nickel-alloys. This research provides an analytical basis for the study of thermodynamic stability of oxide films under different chemical chemistry and a theoretical basis for improving corrosion resistance of different metals and optimizing the chemical conditions of PWR primary circuit.

Enhanced Corrosion Resistance of Carbon Steel in Hydrochloric Acid Solution by Polyoxometalate-Estertin Derivatives.

The development of acid-resistant and efficient corrosion inhibitors is of great significance for metal protection in many industrial processes. In this work, eight cases of sandwich-type polyoxometalate (POM)-based inorganic–organic hybrids, namely, carboxyethyltin and transition metal (TM) cofunctionalized tungstoantimonates and tungstobismuthates, formulated as NaxK10–x[(SnR)2(TM(H2O)3)2(B-β-SbW9O33)2]·mH2O and NayK10–y[(SnR)2(TM(H2O)3)2(B-β-BiW9O33)2]·nH2O (abbreviated as SbW9-TM-SnR and BiW9-TM-SnR; TM = Mn, Co, Ni, and Zn; m = 18, 24, 24, and 22; n = 30, 25, 20, and 21; SnR = Sn(CH2CH2COO)) are first used as green corrosion inhibitors for 20# carbon steel in 0.5–2.0 M HCl solutions. Weight loss and electrochemical experiments prove that the corrosion inhibition efficiency is all above 81% for these POM-based corrosion inhibitors at 150 mg L–1, and SbW9-Mn-SnR shows the highest efficiency of 96.9% at 150 mg L–1 after immersion in a 0.5 M HCl solution for 10 h. Scanning electron microscopy–energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy analyses show that these POM-based inhibitors form films on the carbon steel and the adsorption mechanism obeys the Langmuir adsorption model. The thermodynamic activation parameters were calculated, proving the occurrence of both chemical and physical adsorptions. The film-forming mechanism was also analyzed. This work provides guidance for synthesizing new lacunary POM-based materials to protect metals from corrosion in HCl pickling.

Effect of Heat Treatments on the Corrosion Resistance of Carbon Steel Using Salt Water

The aim of this research is to study the corrosion behavior of carbon steel, because corrosion is common defects that occur to the devices and machinery after manufactured. Plain –carbon steel is considered as one of the most important minerals used in industrial applications. The direct effect on the corrosion behavior of steel is heat treatments because of galvanic corrosion which building up between its microscopic phases. In three methods carbon steel has been treated thermally which the hardening, normalizing, and annealing. Used salt water as corrosive media for a period of (30, 45, 60) days. The steel contains chemical compounds to show its effect on the corrosion. To compare between the results and to determine corrosion rate used weight loss. The results obtained show that the lowest corrosion resistance is for the hardened steel and the corrosion resistance of the annealing steel is the greatest, while the corrosion resistance of the normalized steel is in-between them.

Effects of zinc-aluminium injection on corrosion behaviour and semiconductor properties of carbon steel in the PHT system of PHWR.

Carbon steel is widely used as the piping of the primary heat transport system (PHT) in pressurized heavy water reactors (PHWR). Effects of zinc/aluminum treatment and simultaneous injection of zinc and aluminum on corrosion behavior and semiconductor properties of oxide films formed on carbon steels were characterized by the gravimetric method, potentiodynamic polarization scan, EIS, Mott–Schottky test, SEM, EDS mapping, XPS analysis and photocurrent response measurement. The results showed that all the metal cation ions treatment can improve the corrosion resistance of oxide films in varying degrees. 20 ppb Zn2+ had the greatest enhancement in corrosion resistance, followed by 20 ppb Zn2+ + 20 ppb Al3+. ZnFe2O4, FeAl2O4 and ZnAl2O4 were detected to be new spinel phases generated in oxide films. The oxide films on the surface of carbon steel all demonstrated n-type semiconductor properties. It was worth noting that the total content of manganese and zinc in the oxide film played an important role in the corrosion resistance of carbon steel.

Corrosion behavior of zinc and copper coated structural steels in soil environments

AbstractCorrosion behavior of structural carbon steels grade SS400 coated with copper and zinc exposed to soil sample extracted from the central part of Thailand is studied using weight loss analyses and electrochemical methods, including open circuit potential monitoring for 3600 seconds, electrochemical impedance spectroscopic analyses and potentiodynamic polarization measurements. Bare carbon steels are also examined as a reference. Open circuit potential and polarization resistance of all samples are measured on (1, 2, 3, 4, 7, 10, 15, 30, 45, 60, 77 and 91) days of exposure. Corrosion potential is monitored only on the first and last days. After 91 days, corrosion rate in millimeter per year is calculated from weight loss and corrosion product is characterized. Effects of coating material, thickness and process on corrosion resistance of carbon steel subjected to soil environment are reported and discussed.

Corrosion Resistance of Carbon Steel Modified by a Copper-Carbon Fiber Composite Coating in Seawater

Corrosion Resistance of Carbon Steel Modified by a Copper-Carbon Fiber Composite Coating in Seawater

ВПЛИВ ВИСОКОТЕМПЕРАТУРНОГО ОКИСЛЕННЯ НА КОРОЗІЙНУ СТІЙКІСТЬ ХРОМОСИЛІЦІЙОВАНОЇ СТАЛІ 45

Purpose. Improving the heat resistance and corrosion resistance of carbon steels can be achieved by applying to their surface coatings based on molybdenum and silicon, niobium and silicon, vanadium and silicon, chromium and silicon, which form on the surface protective films of oxides. In this work properties of chromosilicide diffusion coatings applied to steel 45 obtained by the gas method are investigated. Methodology. Diffusion chromosilicide coatings were applied to steel 45 by the gas method. The process was carried out for 6 hours in a closed reaction medium at the pressure of the active gas phase (106 Pa) and a temperature of 1323K. In the work wad studied phase and chemical compositions of diffusion coatings. The heat resistance of the coatings was studied in a specially designed shaft furnace. Corrosion tests were performed by massometric method .The electrochemical behavior of steel and coated steel was studied by the method of removing polarization curves on the potentiostat PI-50.1.1. Results. X-ray diffraction layer analysis revealed that the diffusion layer on the surface of steel 45 consists of two zones - the outer (10–15) 10-6 m, which contains chromium carbides Cr23C6 and Cr7C3 and inner (60–80) 10-6 m, which consists of a solid solution of silicon and chromium α-Fe. The total thickness of the coatings is 100 μm. Microhardness – 19.5 GPa. It was found that chromosilicide coatings obtained by the gas method have high heat resistance up to 1000 С. It is shown that diffusion chromosilicide coatings oxidized at temperatures of 700–800С have higher corrosion resistance in various aggressive environments and a more stable passive state than non-oxidized ones. The degree of protection reaches 99,92–99,99%. Based on the research, a new method of diffusion coatings on the surface of carbon steels with subsequent oxidation was proposed. Practical value. Chromosilicide coatings can be recommended for the protection of machine parts operating at elevated temperatures in various aggressive solution. References 20, tables 1, figures 3.