Određivanje koncentracije Cu2+ iona elektrokemijskim metodama

The possibility of determining the concentration of heavy metal ions, i.e., Cu2+ ions in an aqueous solution of CuSO4 ∙ 5H2O, was tested by electrochemical means. For this purpose, polarisation curves were recorded on a Pt electrode in solutions of known (0.1, 0.5, 1.0, 2.5, 5.0, 7.5, 10.0, 50.0, and 100.0 mM) and unknown concentrations of Cu2+ ions with the reading of the limiting diffusion current. Polarisation measurements were performed in the potential range from open circuit potential to −3.0 V with different potential scan rates (1, 5, 10, 20, and 50 mV s–1). By cathodic deposition on the Pt surface, a reddish-brown copper coating was deposited, the thickness of which increased as the concentration of Cu2+ ions in the solution increased. Furthermore, the limiting diffusion current id increased linearly with the increase in Cu2+ ion concentration, c. The id = f(c) plot was constructed and the unknown concentrations of Cu2+ ions in three randomly prepared CuSO4 ∙ 5H2O solutions were determined. Heavy metal ions from polluted waters (Cu2+ ions) can be successfully removed by electrochemical means, and their concentration determined.Elektrokemijskim putem ispitana je mogućnost određivanja koncentracije iona teških metala, odnosno Cu2+ iona u vodenoj otopini CuSO4 ∙ 5H2O. U tu svrhu su na elektrodi od Pt snimane polarizacijske krivulje u otopinama poznatih (0,1, 0,5, 1,0, 2,5, 5,0, 7,5, 10,0, 50,0, i 100,0 mM) i nepoznatih koncentracija Cu2+ iona uz očitavanje granične difuzijske struje. Polarizacijska mjerenja provedena su u području potencijala od potencijala otvorenog strujnog kruga do –3,0 V uz različite brzine promjene potencijala (1, 5, 10, 20, i 50 mV s–1). Katodnom depozicijom na površini Pt taloži se prevlaka bakra crvenkasto-smeđe boje čija je debljina veća što je koncentracija Cu2+ iona u otopini veća. Nadalje, granična difuzijska struja, id, linearno raste s porastom koncentracije Cu2+ iona, c. Konstruiran je id = f(c) dijagram te su određene nepoznate koncentracije Cu2+ iona u tri nasumično pripremljene otopine CuSO4 ∙ 5H2O. Elektrokemijskim putem uspješno se mogu ukloniti ioni teških metala iz onečišćenih voda (Cu2+ ioni) te odrediti njihova koncentracija

INHIBITION OF ALUMINIUM ALLOY CORROSION IN CHLORIDE SOLUTION BY CAFFEINE ISOLATED FROM BLACK TEA

Caffeine (1,3,7-trimethylxanthine) was isolated from black tea and characterised using different physical methods. The corrosion inhibition performance of the caffeine isolate (in concentration from 110-5 to 110-3 mol/dm3) on aluminium alloy corrosion in neutral 0.5 mol/dm3 NaCl solution was investigated using potentiodynamic and linear polarization measurements at 20 C. Corrosion potential, corrosion current and polarization resistance were determined and surface coverage of inhibitor molecules and inhibition efficiency were calculated. The obtained results show that caffeine effectively inhibited the corrosion reaction in the chloride solution with an inhibition efficiency of up to 76%. Furthermore, caffeine was found to function essentially as a mixed type with a higher influence on cathodic reaction. The adsorption behaviour of investigated inhibitor can be described by the Freundlich adsorption isotherm. The adsorption free energy closes to -10 kJ/mol indicates physical adsorption of the caffeine on the aluminium alloy surface in NaCl solution

BENEFICIAL EFFECT OF CU CONTENT AND AUSTEMPERING PARAMETERS ON THE HARDNESS AND CORROSION PROPERTIES OF AUSTEMPERED DUCTILE IRON (ADI)

The effect of copper content (0.031 wt.% Cu, 0.32 wt.% Cu, 0.51 wt.% Cu and 0.91 wt.% Cu) on the hardness and corrosion properties of ADI was investigated. Samples austenitization were carried out at 850°C for 60 min followed by its austempering at temperatures from 250°C to 420°C for different time (30 to 60 min) in 50% (KNO3 + NaNO3) salt bath. It was concluded that hardness rises with copper content but decreases with higher austempering temperatures and times. The corrosion properties of the samples with minimum and maximum Cu content were investigated by electrochemical methods in 0.5 M NaCl solution. Samples with a higher copper content have shown higher values of polarization resistance (Rp) and lower values of corrosion current (icorr). After polarization measurements, corroded surfaces were analyzed with SEM/EDS analysis

Investigation of Effects of Inhibitor on Corrosion of Carbon Steel in Water with Biocide

U ovom radu istražen je utjecaj komercijalnog inhibitora (Chemtec FI30) na proces korozije ugljičnog čelika P235 u različitim vodenim otopinama; demineraliziranoj i/ili vodovodnoj vodi uz dodatak komercijalnog biocida (Chemtec BI01). Istraživanja su provedena gravimetrijskom metodom i elektrokemijskim metodama, dok je površina ispitivanog materijala analizirana pomoću optičkog mikroskopa. Analize pokazuju da inhibitor smanjuje brzinu korozije ugljičnog čelika u ispitivanim otopinama, ima visoku djelotvornost te da se može svrstati u anodne inhibitore. Također, uočeno je da inhibitor smanjuje opću i jamičastu koroziju ugljičnog čelika u korozivnim vodenim otopinama. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna.The effect of a commercial inhibitor (Chemtec FI30) on the corrosion of P235 carbon steel in water (demineralised and/or tap water) with the addition of a commercial biocide (Chemtec BI01) was studied in the present work. This study was carried out by weight loss and electrochemical methods, while specimen’s surface was examined using optical microscope. Results obtained from gravimetric measurement revealed that P235 carbon steel corroded in aqueous solution, i.e., in a solution of demineralised and tap water (50 : 50) and a biocide (Fig. 1), and in tap water with a biocide (Fig. 5). By analysing the surface of carbon steel with an optical microscope, general and pitting corrosion was observed, which was more pronounced in tap water with biocide (Figs. 2 and 6). The addition of a commercial inhibitor significantly reduced the occurrence of corrosion damage on the surface of carbon steel (Figs. 3, 4, 7, and 8) and decreased the rate of carbon steel corrosion in all aqueous solutions (Table 1). Electrochemical investigations performed by open circuit potential measurement, linear polarisation and potentiodynamic polarisation measurement showed that the inhibitor Chemtec FI03 shifted the potential to more positive values (Figs. 9 and 10), increased polarisation resistance (Table 3), decreased the rate of carbon steel corrosion, and had high efficiency in all tested solutions (Table 4). The results obtained showed that this commercial inhibitor could be used as an effective inhibitor for the corrosion of carbon steel in aqueous media. This work is licensed under a Creative Commons Attribution 4.0 International License

Electrochemical and corrosion behaviour of copper shape memory alloy in NaCl solution

This paper presents a review of electrochemical and corrosion investigations on behaviour of CuAlNi and CuAlMn alloys in NaCl solutions, which were carried out within the framework of the project IP-2014-09-3405“ Design of microstructure and functional properties of copper-based shape memory alloys”, supported by the Croatian Science Foundation. The influence of alloys heat treatment on their corrosion behaviour was investigated, as well as the influence of chloride concentration, pH values and electrolyte temperatures. Cu-shape memory alloys were produced by continuous vertical casting and melt spinning method. Investigations were conducted by electrochemical methods such as open circuit current measurement method, electrochemical impedance spectroscopy method, linear and potentiodynamic polarization. Corroded specimens characterization was obtained by optical and scanning electron microscope. Analysis of the corrosion product composition was carried out by EDS method

Interkristalna korozija Cu-Al-Ni legure u 0.5 mol dm–3 H2SO4 otopini

The corrosion behaviour of Cu-Al-Ni alloy in 0.5 mol dm–3 H2SO4 solution was investigated by electrochemical methods including open circuit potential measurement, electrochemical impedance spectroscopy measurements, linear and potentiodynamic polarization. Measurements were performed in 0.5 mol dm–3 H2SO4 at temperatures 20 and 40 °C. After polarization testing, corroded electrode surfaces were ultrasonically cleaned in deionized water and examined by light and scanning electron microscopy, while the elemental composition at individual points of the alloy surface was determined by EDS analysis. The results of the investigations revealed the occurrence of intergranular corrosion on the Cu-Al-Ni surface, which became more pronounced with increasing temperature. This work is licensed under a Creative Commons Attribution 4.0 International License.Korozijsko ponašanje Cu-Al-Ni legure u 0,5 mol dm–3 H2SO4 otopini ispitivano je elektrokemijskim metodama kao što su mjerenje potencijala otvorenog strujnog kruga, mjerenje metodom elektrokemijske impedancijske spektroskopije, linearne i potenciodinamičke polarizacije. Mjerenja su provedena u 0,5 mol dm–3 H2SO4 pri temperaturama od 20 i 40 °C. Nakon polarizacijskih mjerenja korodirane površine elektroda ultrazvučno su očišćene u deioniziranoj vodi i ispitane svjetlosnim i pretražnim elektronskim mikroskopom, dok je elementarni sastav na pojedinim točkama na površini određen EDS analizom. Rezultati ispitivanja pokazali su da dolazi do interkristalne korozije na površini Cu-Al-Ni legure, čiji intenzitet raste s povećanjem temperature elektrolita. Ovo djelo je dano na korištenje pod licencom Creative Commons Imenovanje 4.0 međunarodna

Effect of heat treatment on corrosion properties of CuAlNi shape memory alloy

The effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% NaCl solution at pH 7.4 and 37 °C by open circuit potential measurements, polarisation techniques, and electrochemical impedance spectroscopy. Investigations were performed on CuAlNi alloy samples in as-cast state and after heat treatment procedure containing annealing at 850, 885 and 920 °C followed by water quenching. Electrochemical impedance measurement results indicate that heat treatment of CuAlNi alloy leads to the increase in charge transfer resistance and surface layer resistance and the decrease in values of capacitance of the double and surface layers, indicating higher corrosion resistance compared with the as-cast CuAlNi alloy. The increase in polarisation resistance and the decrease in corrosion current density of heat-treated CuAlNi alloy also suggest beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Optical microscopy, SEM/EDX and XRD analysis of samples surface after polarisation measurements show the occurrence of pitting corrosion on the electrode surfaces, with the existence of CuCl2, AlCl3 and Cu2Cl(OH)3 compounds as the surface corrosion products

Different corrosion behaviour of CuNi10Fe1Mn alloy condenser tubes in seawater

Two CuNi10Fe1Mn condenser tube samples from boat heat exchangers were investigated due to their different corrosion behaviour in exploitation. One tube was in exploitation nearly 20 years before significant corrosion damage occurred (sample 1), while second tube of different manufacturer showed corrosion damages in 2 months of exploitation (sample 2). In its working conditions seawater was passing through the pipes and R407C gas around the pipes. Chemical analysis, microstructural and hardness investigations and laboratory electrochemical investigations of corrosion behaviour of samples in sea water were performed in order to determine the main reason for different durability of condenser tubes. After electrochemical investigations the polarization surface damage was verified by SEM analysis. Both samples belong to the CuNi10Fe1Mn alloy system with the significant difference in the mass fraction of iron content (around 30% higher for sample 1). Samples coincide in the structural sense (type and size of grain) and in mechanical properties (hardness of 133 HV1). Fe content in the CuNi10Fe1Mn alloy has the key role in the corrosion behaviour of the tested samples. It has been found that (regardless of the temperature of the heat exchanger) the corrosion resistance of the tested samples increases with increasing Fe content in the alloy. Namely, the corrosion current decreases in same order, while the polarization resistance and properties of surface oxide layer increase. SEM analysis confirmed less damage on the surface of samples with higher Fe content

Different corrosion behaviour of CuNi10Fe1Mn alloy condenser tubes in seawater

Two CuNi10Fe1Mn condenser tube samples from boat heat exchangers were investigated due to their different corrosion behaviour in exploitation. One tube was in exploitation nearly 20 years before significant corrosion damage occurred (sample 1), while second tube of different manufacturer showed corrosion damages in 2 months of exploitation (sample 2). In its working conditions seawater was passing through the pipes and R407C gas around the pipes. Chemical analysis, microstructural and hardness investigations and laboratory electrochemical investigations of corrosion behaviour of samples in sea water were performed in order to determine the main reason for different durability of condenser tubes. After electrochemical investigations the polarization surface damage was verified by SEM analysis. Both samples belong to the CuNi10Fe1Mn alloy system with the significant difference in the mass fraction of iron content (around 30% higher for sample 1). Samples coincide in the structural sense (type and size of grain) and in mechanical properties (hardness of 133 HV1). Fe content in the CuNi10Fe1Mn alloy has the key role in the corrosion behaviour of the tested samples. It has been found that (regardless of the temperature of the heat exchanger) the corrosion resistance of the tested samples increases with increasing Fe content in the alloy. Namely, the corrosion current decreases in same order, while the polarization resistance and properties of surface oxide layer increase. SEM analysis confirmed less damage on the surface of samples with higher Fe content

Effect of heat treatment on corrosion properties of CuAlNi shape memory alloy

The effect of heat treatment on corrosion properties of CuAlNi shape memory alloy was investigated in 0.9% NaCl solution at pH 7.4 and 37 °C by open circuit potential measurements, polarisation techniques, and electrochemical impedance spectroscopy. Investigations were performed on CuAlNi alloy samples in as-cast state and after heat treatment procedure containing annealing at 850, 885 and 920 °C followed by water quenching. Electrochemical impedance measurement results indicate that heat treatment of CuAlNi alloy leads to the increase in charge transfer resistance and surface layer resistance and the decrease in values of capacitance of the double and surface layers, indicating higher corrosion resistance compared with the as-cast CuAlNi alloy. The increase in polarisation resistance and the decrease in corrosion current density of heat-treated CuAlNi alloy also suggest beneficial influence of heat treatment on corrosion resistance of CuAlNi alloy. Optical microscopy, SEM/EDX and XRD analysis of samples surface after polarisation measurements show the occurrence of pitting corrosion on the electrode surfaces, with the existence of CuCl2, AlCl3 and Cu2Cl(OH)3 compounds as the surface corrosion products