Inhibierung der Korrosion von Kupfer in Natriumhydroxidlösungen

Inhibition of copper corrosion in sodium hydroxide solutions The authors have investigated the effect of 30 organic substances on the corrosion of copper in aqueous NaOH solutions (0.2, 0.5 and 1.0 n). The following substances were found to be effective inhibitors: resorcin, phloroglucin, pyragallol, tanni, β-naphthom, m and p-aminophenol, glucose, furfural, cyclohexanon, 8-oxychinolin, hydrazine sulphate, chinalizarine, hydrochinon, sodium diethyldithiocarbamate, sodium rhodizonate, gallocyanine and acriflavine. In most cases, the inhibition effect is due to a covering layer of reaction products of metal, inhibitor and hydroxide. The decisive factor is the stability of the covering layer with the different lye concentrations.     

Untersuchungen zur Wirksamkeit des Natriumsalzes der 1-Hydroxyethan-1,1-diphosphonsäure als Inhibitor für Kupferwerkstoffe in Kühlwasser

Investigations on the efficiency of sodium salt of 1-hydroxyethan-1,1-diphosphonic acid as inhibitor for copper materials in cooling water The effect of sodium salt of 1-hydroxyethan-1,1-diphosphonic acid on the corrosion rates of copper, CuZn30, CuZn20A12 and CuNi10Fe1Mn in cooling water was investigated gravimetrically using a recirculating loop. In the presence of zinc ions sodium salt of 1-hydroxyethan-1,1-diphosphonic acid decreases corrosion rates. This phosphonate in connection with zinc salt is a promising inhibitor for CuZn20A12 in cooling water circulating systems.     

2-Benzimidazolthiol als Korrosionsinhibitor für Kupfer in Essigsäure und Salzsäure

2-Benzimidazolethiol as a corrosion inhibitor for copper in acetic acid and hydrochloric acid solutions An attempt has been made to evaluate the inhibitive power of 2-benzimidazole-thiol for corrosion of copper in acetic acid and hydrochloric acid solutions. The substance acts as an excellent inhibitor for copper in both the systems. This inhibitive action of 2-benzimidazolethiol can be attributed to chelate formation with the metal ion. Polarization measurements reveal that the inhibition is governed principally by the cathodic polarization.     

Sulfathiazole as potential corrosion inhibitor for copper in 0.1 M NaCl

Effects of sulfathiazole (ST) on copper corrosion as a corrosion inhibitor in 0.1 M NaCl solutions have been studied using potentiodynamic polarization, open circuit potential, electrochemical impedance spectroscopy with scanning electron microscopy (SEM). Potentiodynamic polarization measurements indicated that the presence of ST in chloride solutions affects mainly the cathodic process and decreases the corrosion current and shifts the corrosion potential towards more negative values. The adsorption of inhibitor on the copper surface obeys the Langmuir adsorption isotherm. The adsorption free energy of ST on copper (?33.47 kJ/mol) shows a strong adsorption of the inhibitor on the metal surface. The effect of temperature on the inhibition efficiency of sulfathiazole was examined with Arrhenius equation and activation energies in 0.1 M NaCl with and without inhibitor were calculated. Impedance data were analyzed using an appropriate equivalent circuit model for the electrode /electrolyte interface. SEM measurements also exhibited that the ST molecules are strongly adsorbed on the copper surface.     

Untersuchung des SwRK-Verhaltens des hochreinen martensitaushärtenden Stahles X5CrNiCuNb 17 4 PH im Vergleich zum weichmartensitischen Stahl X4CrNiMo 16 5 1 ESU in chloridhaltigen wäßrigen Medien. Teil 2: SwRK-Untersuchungen und Rißeinleitungsmechanismen

Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel X5CrNiCuNb 17 4 PH in comparison to the soft martensitic stainless steel X4CrNiMo 16 5 1 ESR in chloride containing aqueous media — Part 2: Corrosion fatigue tests and crack initiation mechanisms The following report concerns the study of the corrosion fatigue behaviour of the soft martensitic steel X4CrNiMo 16 5 1 ESR and the precipitation hardened X5CrNiCuNb 17 4 PH in sodium solution in the temperature range between 20° and 150 °C and the determination of their general corrosion properties and the mechanism of crack propagation. Their corrosion fatigue limits were compared with each other. A comparision was also made between an electro-slag-remelted soft martensitic steel and a charge without an ESR aftertreatment. Microfractographical fracture and crack path investigation were carried out for interpretation of the experimental results. It was observed that in both super pure steels (soft martensitic and precipitation hardened) the oxidic inclusions are not responsible for the crack intiation, as it was found in the non ESR treated steels. In the 17-4 PH steel copper containing inclusions in the crack initiation areas were observed. In concentrated sodium solution pitting corrosion was found at both steels.     

Impedance spectroscopic study of corrosion inhibition of copper by surfactants in the acidic solutions

The inhibitive action of the four surfactants, cetyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate, sodium oleate and polyoxyethylene sorbitan monooleate (TWEEN-80), on the corrosion behavior of copper was investigated in aerated 0.5 mol dm⁻³ H₂SO₄ solutions, by means of electrochemical impedance spectroscopy. These surfactants acted as the mixed-type inhibitors and lowered the corrosion reactions by blocking the copper surface through electrostatic adsorption or chemisorption. The inhibitor effectiveness increased with the exposure time to aggressive solutions, reached a maximum and then decreased, which implies the orientation change of adsorbed surfactant molecules on the surface. CTAB inhibited most effectively the copper corrosion among the four surfactants. The copper surface was determined to be positively charged in sulfuric acid solutions at the corrosion potential, which is unfavourable for electrostatic adsorption of cationic surfactant, CTAB. The reason why CTAB gave the highest inhibition efficiency was attributed to the synergistic effect between bromide anions and positive quaternary ammonium ions. C₁₆H₃₃N(CH₃)₄⁺ ions may electrostatically adsorbed on the copper surface covered with primarily adsorbed bromide ions. On the basis of the variation of impedance behaviors of copper in the surfactant-containing solutions with the immersion time, the adsorption model of the surfactants on the copper surface was proposed.     

Inhibierung der Korrosion von Kupfer in salzsauren Lösungen

Inhibition of copper corrosion in hydrochloric solutions Furfural is one of the best corrosion inhibitors of copper in hydrochloric acid. The inhibition effect ranges from 90 to 100 per cent. With increasing acid concentration, the quantity of furfural required for effective corrosion inhibition becomes smaller. By means of polarisation measurements, it can be found that, in 0.2 n and 1.0 n HCl, the inhibitor has an essential anodic effect and the cathode becomes depolarised whilst, in 2.0 n and 3.0 n HCl, the anodic zone is virtually unchanged and there is a considerable polarisation in the cathodic zone. The protective effect of furfural is probably due to its resin forming capacity.     

The influence of adenine on corrosion of copper in chloride solutions

The influence of the concentration of adenine (AD) on the corrosion and the spontaneous dissolution of copper in 1.0 M NaCl solutions of pH 6.8 was studied. The investigations involved electrochemical polarization methods as well as weight loss measurements, quartz crystal microbalance (QCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency increases with an increase in the concentration of AD. An adherent layer of inhibitor is postulated to account for the protective effect. The adsorption of adenine has been found to occur on the surface of copper according to the Langmuir isotherm. The values of standard free energies of adsorption suggest chemical adsorption of AD on copper surface. The use of adenine can effectively prevent various new installations made of copper and exposed to the action of aqueous solutions of chlorides from corrosion damage.     

Dithio-oxamide as inhibitor of Copper corrosion in chloride solutions at various ph values

This paper investigates the inhibiting properties of dithiooxamide (DTOA) towards copper corrosion in chloride media at different pH values. The aggressive solutions were prepared by dissolving 0.1 M sodium chloride in a Britton Robinson buffer, adjusted at the pH values of 3, 5, 7 and 9. The inhibitor was tested at the concentration of 10^?3 M. The inhibiting efficiency of DTOA was evaluated after 20 days of immersion in the solutions at the temperature of 30°C. Both dc (polarization curves and voltammetric tests) and ac (electrochemical impedance spectroscopy, EIS) electrochemical tests were performed to elucidate the inhibition process. The results indicate that DTOA affords its best inhibiting efficiency at pH 5 and 7, but even at pH 3 it can retard the corrosion process. On the contrary, at pH 9 it stimulates the corrosion process. Between pH 3 and 7, the additive is reputed to form a protective film of Cu(II)DTOA salt, which is formed through a two step oxidative process, probably involving Cu(I)DTOA as an intermediate. The EIS analysis indicates that in chloride solutions copper fits a model of a partially blocked electrode. This analysis suggests that at pH 3 and 7 the film produced on copper by DTOA has a lower porosity than that of the oxide or cuprous chloride films formed in non inhibited solutions, thus hindering the mass transport through the layer.     

Inhibitive effect of sodium eperuate on zinc corrosion in alkaline solutions

The effect of sodium eperuate prepared from Wallaba (Eperua falcata Aubl) extract on zinc corrosion was investigated in alkaline solutions with chloride ions (i.e., simulated concrete pore solutions) by using electrochemical techniques. Sodium eperuate inhibits the corrosion of zinc in 0.1 M NaCl solutions with pH 9.6. As its concentration increases to 1 g/L, the inhibition efficiency reaches approximately 92%. In alkaline solutions with pH 12.6, sodium eperuate has no adverse effect on passivity of zinc, and retards the chloride attack. These suggest that sodium eperuate is an effective inhibitor for the protection of zinc in alkaline environments.     

钼酸钠和三乙醇胺对铜的缓蚀作用

利用极化曲线法研究了钼酸钠以及钼酸钠和三乙醇胺以特定的配比形成的复合缓蚀剂对铜的缓蚀作用.结果发现：单独使用钼酸钠时，缓蚀效果不明显;钼酸钠与三乙醇胺的协同作用时，钝化区显著增宽，缓蚀效果提高，且所需剂量更少，表明钼酸钠和三乙醇胺共同作用在去离子水中及在含5×10-3 g/L Cl-的去离子中对铜具有明显的协同缓蚀作用.且当钼酸钠为300 mg/L，三乙醇胺也为300 mg/L时，协同缓蚀效率最高.      

Effect of nitrite in corrosion of reinforcing steel in neutral and acid solutions simulating the electrolytic environments of micropores of concrete in the propagation period

Inhibitors in concrete are usually used to be effective in alkaline or neutral solutions, however, when corroding by chlorides, there is a local acidification and therefore it is necessary to study the effect of the inhibitor in acid pH values. Measurements of the corrosion rate of corrugated steel bars have been carried out in solutions simulating electrolytic chloride environments in the micropores of concrete in the propagation period. It has been studied the effect of sodium nitrite as a corrosion inhibitor when added to the mentioned solutions. The solutions considered consisted of sodium chloride for neutral condition and ferrous chloride for acid condition. This is the soluble compound produced during the corrosion of steel as a result of chloride attack. Comparison of the results of polarization resistance with gravimetrically determined weight losses are presented. Also, results of electrochemical impedance spectroscopy are presented here. It has not been observed a significative improvement in using nitrite as inhibiting agent in these systems. The corrosion seems to be related to the [Cl⁻]/[OH⁻] ratio in three different regions of pH identified from acid to alkaline pH values.     

挤压态Mg99.2Ca0.6Mn0.2合金的力学行为及腐蚀性能研究

研究了挤压态Mg99.2Ca0.6Mn0.2镁合金的位伸行为和压缩行为,探讨了合金在不同PH值的SBF模拟体液中的电化学极化曲线和阻抗谱,以评定合金的腐蚀性能,为镁合金植入材料的制备提供依据。结果表明：挤压态Mg99.2Ca0.6Mn0.2合金表现出准解理断裂的特征,抗拉强度、屈服强度、延伸率分别为279 MPa、251 MPa和11%,抗压强度为330 MPa。腐蚀介质的PH值对合金的腐蚀性能有显著影响。随着腐蚀介质PH值升高,阻抗谱弧半径大幅度增大,合金的腐蚀电位升高,腐蚀电流密度降低,合金的腐蚀速率明显下降。在阻抗谱的低频端出现了一个时间常数。PH值为7.2和10的SBF溶液中的瞬时腐蚀速率分别为4.1 mm/a和0.2 mm/a。     

Corrosion of copper by food acids containing colourants and sweetening agents – Part II: Corrosion by tartaric acid

The corrosion of copper in tartaric acid solutions containing various food colourants and/or sweetening agents has been studied with respect to the concentration of the acid and the colourant, and temperature. At constant acid concentration the corrosion increases with the concentration of the colourant whereas at constant colourant concentration it increases with acid concentration. In acid solutions the corrosivity of the colourant increases in the order: tartrazine < ponceau 4 R < carmoisine < amaranth < fast red E < sunset yellow. The addition of sweetening agent also increases the corrosion of copper, the corrosion increasing in the order: saccharin < fructose < glycerol < sucrose < glucose. In acid containing the colourant as well as the sweetening agent the order of corrosivity is: sucrose < glucose < fructose < saccharin < glycerol. Copper in 0.05 M tartaric acid develops a corrosion potential of ?40 V (vs SCE). The addition of colourants or sucrose do not appear to have any effect on the corrosion potential. Galvanostatic polarisation curves show very little anodic but appreciable cathodic polarisation. Additives like sodium benzoate, raspberry essence, gum tragacanth, dextrin, and potato starch appear to confer some protection to copper in tartaric acid containing colourants like carmoisine.     

Untersuchungen zum Einfluß von Polyphosphat auf das Korrosionsverhalten von Kupfer in Elektrolytlösungen

Experiments on the effect of polyphosphate on the corrosion behaviour of copper in electrolytic solutions Gravimetric experiments in a circulating equipment were performed on the effect of Graham salt on the corrosion behaviour of copper in electrolytic solutions by means of a high confounded 2^7?4-fractional factorial. The composition of copper samples: 99.7% Cu, 0.002% Bi, 0.005% Sb, 0.01% As, 0.05% Fe, 0.2% Ni, 0.01% Pb, 0.05% Sn, 0.01% S. The aqueous electrolytic solutions contained hydrogencarbonate-, sulphate-, chloride-, nitrate-, manganese-, calcium ions and Graham salt. It appears that Graham salt is unsuitable for the inhibition of copper corrosion. The polyphosphate promotes corrosion. Chloride-, nitrate-, sulphate- und manganese ions also increase corrosion rate whereas it is decreased by hydrogencarbonate ions. Increase of temperature also causes a decrease of corrosion rate. An existing danger of contact corrosion induced by copper cannot be removed by addition of Graham salt if copper and carbon steel, respectively galvanized steel are installed together in equipments of plant water.     

Untersuchung vielkomponentiger,Nitrilotrimethylenphosphonsäure enthaltender Systeme als Inhibitoren für den Metallschutz in neutralen wäßrigen Medien

Study of multicomponent systems containing nitrilo-trimethylene phosphonic (NTMP) acid as inhibitors for the protection of metals in neutral aqueous media The inhibitor mixtures studied contain nitrilo-trimethylene phosphonic acid, oxalic acid or phthalic acid anhydride and zinc sulfate. On the basis of the measurement of the differential electric double-layer capacity using the bridge method the thermodynamic characteristics of the adsorption of the compounds studied and their mixtures on the surface of armco iron have been determined in aqueous potassium fluoride solutions. The best inhibitor mixture was then used as the starting material for optimizing the composition ratios. Using gravimetric techniques the influence of this mixture on the rate of corrosion of steel ST3S in simulated industrial water of variable chemical composition and in water being chlorinated. In addition the influence of this mixture on the rate of corrosion of copper (Cu 99,9 E), brass (CuZn 37), zinc (97,5) and aluminum alloy (AlCu4Mg1) has been studied as well and considerable decrease of the corrosion rate by the inhibitor mixtures has been established. Nitrilo-trimethylene phosphonic acid, in combination with phthalic acid anhydride and zinc ions can therefore be considered as a perspective inhibitor for the corrosion protection of industrial cooling and heating water installations.     

Zum Potentialverhalten der Oberfläche metallischer Werkstoffe bei milder und starker Schwingungskavitation – IV. Aluminium- Werkstoffe

The potential behaviour of the interphase of metallic materials at mild and strong vibratory cavitation IV. Aluminium-base materials In continuation of the reports already published in previous issues of this periodical the authors present results obtained with aluminium base materials, and in particular pure aluminium, AlMg 5, AlZnMgCu 1.5 and AlCuMg 2. The aggressive media used were sodium chloride solutions and artifical sea water. The potential shift is rather small, even under moderate cavitation conditions; only at rather high accélérations (up to 65000 g and more) the potential displacement may exceed ?500 mV. The copper containing alloys form an exception because their potential is constant in the aerated sodium chloride solution in the range of intensities studied. In cases when the protective layer is destroyed and the potential is shifted to more negative values attention has to be paid to the danger of accelerated corrosion in addition to erosion corrosion.     

Über die Werkstoffzerstörung durch Kavitation und Korrosion in Äthylenglykol-Wasser-Gemischen

The destruction of material through cavitation and corrosion in ethylene glycol-water mixes Destruction of structural parts in contact with liquids through cavitation and corrosion is the consequence of complex mechanical and corrosive stresses. In recent years, extensive research at model test beds has yielded information on the stress conditions encountered in waters. It was now intended to ascertain to what extent the destruction of material through cavitation and corrosion in ethylene glycol-water mixes differs from that in waters. For this purpose, tests have been carried out with magnetostrictive oscillators on grey cast iron and copper in water, in ethylene glycol, and in mixes of both liquids; the tests on grey cast iron were extended to solutions with inhibitor additives. It was found that the mechanical stress through cavitation is about the same in the liquids investigated. Certain differences in the destruction rate are mainly due to the high boiling point of ethylene glycol and the corrosion resistance of the material concerned. In aqueous ethylene glycol solutions as well as in water, the damage can be reduced by the addition of corrosion inhibitors.     

NaDDC as a corrosion inhibitor of brass

The carbamate turns out to be a good inhibitor of the corrosion of brass (80/20 and 59/41) in 0.5 N sodium chloride, 1.0 n sodium hydroxide and buffer solutions (NaOH and citric acid, pH 4.4-6.0). The inhibiting effect depends on inhibitor concentration, so that in some cases corrosion may even be stimulated. The inhibitor effect is attributed to the formation of insoluble complexes with the two alloy components.     

1—HBTA对钢,黄铜的缓蚀作用

研究在3％NaCl水溶液和模拟冷却水介质中,不同pH值时不同浓度(0.05％、0.1％、0.5％)的1-羟基苯骈三氮唑(以下简称1-HBTA)对钢、黄铜的缓蚀作用,1-HBTA是一种阳极型缓蚀剂,对金属腐蚀的阳极过程有明显的阻滞作用,而对阴极过程影响不大。