Die Wasserstoffaufnahme von Eisen bei der Korrosion in neutralen bis schwach sauren Elektrolyten

Hydrogen uptake by iron during corrosion in neutral to weakly acid electrolytes During atmospheric corrosion and corrosion by aqueous solutions, hydrogen can enter into steel. The hydrogen activity built up in iron during corrosion by dilute aqueous solutions of hydrochloric acid, sulfuric acid and iron salts has been measured as a function of pH using a permeation technique. Below pH = 5 in oxygen free solutions and pH = 4 in air saturated solutions the hydrogen activity \documentclass{article}\pagestyle{empty}\begin{document}$ a_{\rm H} {\rm = }\sqrt {{\rm p}_{{\rm H}_{\rm 2} } {\rm /(}\mathop {{\rm p}_{{\rm H}_{\rm 2} } }\limits^{\rm o} {\rm = 1}\,{\rm bar)}} $\end{document} reaches values of more than 0.1 sufficient to cause delayed cracking of steels susceptible to hydrogen embrittlement. The anions and Na⁺-ions have no markable influence. The influence of Fe³⁺ and O₂ is discussed.     

Korrosion von Klebverbindungen

Corrosion of adhesive bonds Today the topic of the adhesive bond technology is no more the realization of a strong adhesion directly after curing the adhesive and before the bond has been exposed to any environmental load. As a rule this is possible even in the case of oiled steel sheets for the body-in-white in the automotive industry. For plastics which are difficult to bond (e.g. polyolefines) suitable surface pretreatments are available. The mechanical loads at “normal” temperatures can be controlled by the static and dynamic strength of the adhesive and by the design of the adhesive bond, even if there is a high expenditure for performing all the tests, because for most of the applications the available data basis is insufficient. Most important for the reliability of the adhesive bonding technology is the long-term durability under environmental loads, e.g. moisture. Three aspects of the durability have to be differentiated depending on the location and on the way of the influence of the medium: • diffusion-dominated durability of the polymer • adhesion-dominated durability • corrosion-dominated durability     

Selektive Korrosion von Kupfer-Zink-Legierungen

Selective corrosion of copper-zinc-alloys Starting from recent ideas on the mechanism of corrosion the most important parameters – with respect to materials properties and water chemistry – of dezincation, pitting and intercrystalline corrosion of CuZn alloys are explained. Dezincation is increased if the alloy contains β-phase (duplex brass). Within certain limits of chloride and sulphate content dezincation of these materials can be prevented by an increased hydrogencarbonate concentration of the medium. At pure α-brass dezincation is preceded by local cestruction of the natural protection layer. Intercrystalline corrosion occurs preferentially at α-brass if the material contains precipitations at the grain boundaries. Intercrystalline attack is favoured by higher temperatures, coarse-grained microstructure, higher contents of the alloying elements arsenic and phosphorus as well as from the water-side by ammonia and the activity of aeration elements.     

Korrosion von Bauelementen in der Mikroelektronik

Corrosion of parts used for microelectronics applications Manifestations of corrosion on parts used in microelectronics occur for different reasons and are frequently described in literature. They are not only caused by operational circumstances but are also favoured by the production process. Investigations have been carried out to ascertain the cause of the failure of several circuit boards used in the operation electronics of the preparation unit for kitchen waste water. During microscopic and electronmicroscopic observations of failed circuit boards, different corrosion types have been found, mainly on the surface of a commonly used Sn-Pb-alloy. Hence, potentiostatic and free-corrosion experiments under laboratory conditions have been performed using the employed Sn-Pb-alloy. In order to simulate the increased concentration of harmful substances at the surface of the boards, the medium used contained a high percentage of the substances found in the surroundings of the unit. From the measured values of current density for different potentials and the observed corrosion on the sample's surface, conclusions as to the reported failure of the electrical operation system have been made. During the experiments under laboratory conditions, manifestations of corrosion similar to those found on the surface of the failed circuit boards have been observed. Based on these results, it seems likely that pitting and selective corrosion of the Sn-Pb-alloy led to the failure of the investigated circuit boards and, therefore, of the operation electronics.     

Zur Korrosion von Kupferwerkstoffen in Tetrachlorkohlenstoff

Corrosion of copper base materials in carbon tetrachloride Copper (OFHC), two copper zinc alloys (CuZn36 and CuZn15), one nickel-copper alloy (NiCu30Fe), the copper tin casting alloy G-CuSn10, and the copper aluminium casting alloy G-CuAl10Fe were immersed in the following boiling media: carbon tetrachloride dried over P₄O₁₀, carbon tetrachlorid saturated with water and two phase mixtures of carbon tetrachloride and water. The individual samples were positioned within the organic phase, within the aqueous phase, within the vapour phase and within the condensated phase, respectively. OFHC copper, NiCu30Fe, CuZn15 and G-CuAl10Fe are corrosion resistant (corrosion rate ≤ 0,01 mm/y) in dry as well as in water saturated CCl₄. The same statement is valid for alloys CuZn36 and G-CuSn10 which show a corrosion rate of approximately 0,02 mm/y within the condensate of CCl₄ saturated with water. All alloys exhibit more or less corrosion within the two phase mixtures. Within the aqueous phase the materials do not prove to be resistant: they are completely dissolved in less than 30 days. Paralle to the corrosion of CuZn36 and G-CuAl10Fe zinc and aluminium, respectively, went into solution. The vapour phase above the carbon tetrachloride-water mixture consisted of over 90% by volume carbon monoxide. This prove that the corrosion of all materials which had been immersed in the aqueous phase was effected by phosgene.     

Korrosion von Aluminium in Salzgemischen und Korrosionseinfluß von Kupferionen

Corrosion of aluminium in mixtures of salts and effect of copper ions Corrosion of aluminium has been studied in stagnant condition, in mixtures of salts, NaCl + NaHCO₃, Na₂CO₃ + NaHCO₃ and NaCl + Na₂CO₃; effect of addition of copper ions has also been studied. It has been found that (shallow) pits are formed only when both chloride and bicarbonate are present. Addition of copper ions occasionally increases the numbers of pits but may some times decrease corrosion.     

Kathodische Korrosion von Blei im Erdboden

Cathodic corrosion of lead in the soil Cathodic corrosion of lead in the soil can be expected in exceptional cases only. The corrosion found on a particular lead cable could be simulated in the laboratory. It could be confirmed, that — probably by decomposition of primary lead hydride — metallic lead is deposited below layers of Ca and Mg compounds already at potentials below ?1,7 V. A special switching method was developed to account for breakthrough polarisation.     

Zur Korrosion von Werkstoffen der Mikroelektronik

On the corrosion of materials in the field of microelectronics The reliability of microelectronic components and devices is also determined by the corrosion behaviour of the applied materials. Because of the very small dimensions of the resulting corrosion systems, the transferability both of the experimental methods and of the interpretation of results, known from macrodimensioned corrosion systems, is only possible with some restrictions. Micro-dimensioned corrosion systems, occurring in the field of microelectronics, are characterized by a complex mechanical, thermal and corrosive load, which can change very rapidly over time, by the presence of different, galvanic coupled metals and at least by an electrical load of the corroding material. This report describes the corrosion types and problems of microelectronical corrosion systems, concerning the experimental simulation of corrosion reactions and the evaluation of the results.     

Korrosion im Inneren von integrierten Schaltkreisen

Corrosion in the interior of integrated circuits The present contribution deals with corrosion phenomena in the interior of integrated circuits, not, however, phenomena occurring on the external surfaces of the ic housings or on the circuit board as such. The paper is further restricted to phenomena occurring in ic's and on discrete semiconductors based on silicon, since distinctly more than 90% of all the semiconductor elements are based on silicon; III-V-compound semiconductors are not included in the present treatment.     

Einfluß der Hydrodynamik auf die Korrosion von Eisen und Stahl in neutralen belüfteten NaCl- und Na2SO4-Lösungen

Influence of hydrodynamics on the corrosion of iron and steel in neutral aerated NaCl and Na₂SO₄ solutions The corrosion behaviour of iron and steel in aerated neutral NaCl and Na₂SO₄ solutions is mainly determined by the transport-controlled cathodic oxygen reduction. Its reaction zone depends on the physical and chemical properties of the 3-D layer formed on the corroding surface. The influence of hydrodynamics is restricted to the transport of the dissolved oxygen to the reaction zone. The obtained results are independent of laminar or turbulent flow conditions.     

Zur Korrosion von Aluminium-Werkstoffen in Salpetersäure

Corrosion of aluminium and aluminium alloys in nitric acid A literature survey was made to show the suitability of aluminium and aluminium alloys in contact with highly concentrated nitric acid, particularly with regard to the corrosion behaviour of weld joints made using various welding processes. The corrosion resistance of Al99.5 in nitric acid was investigated as functions of temperature and acid concentrations. The linear corrosion rates are plotted in an Arrhenius diagram. Decreasing nitric acid concentrations are causing a parallel shift of the lines in the Arrhenius diagram towards higher corrosion rates. Starting with A199.5, the corrosion rates in nitric acid at and above 99.8 concentration decrease as the A1 contents of the materials increase. Doping with copper should be avoided. After exposure of wrought as well as continuously cast A1 and A1 alloys to highly concentrated technical grade nitric acid at 30 °C (1 year test period), the corrosion behaviour of a number of alloys was comparable to that of pure aluminium grades.     

Zur Kinetik der Korrosion von Metallen in Halogenkohlenwasserstoffen

Kinetics of metal corrosion in halogenated hydrocarbons The corrosion kinetics of non alloyed steel in the solvents Trichloroethylene, Perchloroethylene, 111-Trichlorethane has been investigated. Parameters are water content, the temperature and the concentration of Dibromethane. Thermodynamic calculations show that Fe and Al in contact with HKW may corrode. Investigations into the rate of hydrolysis give increasing values in the sequence Trichloroethylene – Perchloroethylene – 111-Trichloroethane. In absolutely pure HKW iron is not corroded, but in presence of water, especially if it is present as a secondary phase, strong corrosion attack occurs. An incubation time is interpreted as the time for the build-up of critical concentration of aggressive agents in the aqueous phase. Aluminium may be corroded electrochemically (in two phase HKW/water mixtures) as well as by a radical (metalorganic) mechanism. It is shown that the incubation time of the system Al/C₂H₄Br₂ is connected with the build-up of a critical radical concentration at the metal surface. During the investigations into the system Al/C₂H₄Br₂ the enthalpie production has been used for measuring the corrosion rate.     

Zur Korrosion von Lötverbindungen

Corrosion of brazed joints A soldered electrical PtNi contact was attacked in air with formation of Pb (OH)₂ · (PbCO₃)₂. This corrosion product, because of its dielectric properties, deteriorated the contact performance of the Pt? Ni couple. It is therefore recommended not to use lead containing alloys for soldering electrical contacts.     

Korrosion von Chemieemail in alkalischen Lösungen

Corrosion of chemical service glass-enamel in alkaline solutions Chemical service glass-enamels are high resistant, multi component silicate glasses fused onto steel yielding a compound material of mechanical and chemical stability as well. The resistance of these glass-enamels against alkali attack is investigated in laboratory tests involving gravimetric evaluation of totally glass-lined steel samples after contact with various alkaline media. Thus the influence of the following technically relevant parameters on the glass corrosion rate becomes perceptible: agitation and renewal of the medium, volume-to-surface ratio, exposure time, temperature, alkali content, glass quality; special attention is paid to inhibition effects originating e. g. from calcium(II) ions. These results may help to conceive on a laboratory scale a corrosion test for glass-linings which simulates in good approximation service conditions. In consequence, the corrosion situation in glass-lined equipment becomes more evident and appropriate measures may be considered to improve its economy.     

Die Korrosion von Messing in Ammoniumchloridlösungen

Corrosion of brass in ammonium chloride solutions The corrosion behaviour of brass (Cu77Zn21A/2, with and without addition of As) has been investigated in 0.01 to 1 M ammonium chloride solution of PH 4 and 2, and in solutions 1 M in chloride ion, with variable Na⁺ and NH⁺₄ concentrations (total concentration 1 M in each case), at pH 4 and 2. While arsenium-free brass was attacked by dezincification in most cases, intercrystalline corrosion was found on As-containing brass. The latter type of corrosion is found already at As contents as low as 0.01%. In a medium 1 M in chloride ion intercrystalline corrosion is found at PH 2, irrespective of the ammonium ion concentration, while at PH 4 intercrystalline corrosion is found only at higher ammonium ion concentrations (practically 1 M). The intercrystalline corrosion was found to be due to the segregation of Zn and As respectively at the grain boundaries and to the influence of As on the stability of the CuCl^?₂ formed by the anodic reaction. The influence of the solution composition on the progress in time of the intercrystalline corrosion is explained.     

Quantenchemische Bewertung von Nitron als Inhibitor der Korrosion

Quantum chemical evaluation of Nitron as a corrosion inhibitor Eliminating as much as possible the physical factors which might have a bearing, the efficiency of Nitron (having meso-ionic structure) as an inhibitor of the corrosion of Fe 99.999 in 5% HCl has been investigated and evaluated in terms of quantum chemistry. According to this evaluation the inhibiting efficiency increases with the energy of the HOMO because the ionisation potential is then reduced and the molecule can more easily act as an electron donator. Certain positions in the Nitron molecule which are characterized by increased electron density are thus in a position with their own electrons to participate in the bond formation between inhibitor and metal.     

Untersuchungen zum Umwandlungsverhalten von InSn-Legierungen bei selektiver Korrosion

Investigation of phase transformations induced by the selective dissolution of In from InSn alloys . In the context with the theory of dealloying the selective dissolution of In from InSn alloys has been investigated. As a consequence of their low melting-point the corrosion behaviour of these alloys differs significantly from the behaviour of higher-melting alloys. For the β-InSn phase this is illustrated by the result that a Sn-content of 20 at.%, supported by a porous morphology of the γ-SnIn product phase, does not excert a significant influence on the In-dissolution kinetics. Selective dissolution of In from γ-SnIn and from the β-Sn terminal phase is controlled, however, by solid-state diffusion of In to the electrode surface. Under these circumstances the product phase β-Sn that results from the removal of In from γ-SnIn at room temperature grows with a morphological stable interface and the concentration profiles within the interdiffusion zones can be directly detected by electron microprobe analysis.     

Zum Einfluß von Chlorid-Ionen auf die Korrosion von unlegiertem Stahl in Wasserversorgungsanlagen

Considerations on the effect of chlorides on corrosion of unalloyed steel in plants for water supply The effect of anions of neutral salts, especially the chloride anions on corrosion of steel in tap water is discussed in terms of the theoretical aspects and explanations according to DIN 50 930 part 2. For a better understanding it is useful to separate the different corrosion effects: uniform corrosion attack, local corrosion attack and transfer of corrosion products into the water. With respect to these different effects test results are evaluated. It is shown, that neutral salts have no effect on uniform or local corrosion, whereas there is a marked effect of other water parameters. The transfer of corrosion products into the water is controlled by neutral salts as well as by alkalinity, pH, service conditions and the age of the plant.     

Die Korrosion von Kupfer-Aluminium-Legierungen in schwefelsaurer Beizlösung

Corrosion of copper-aluminium alloys in sulfuric acid containing pickling solutions Wrought copper aluminium alloys (aluminium contents between 5 and 10 weight-%, additions of Fe, Ni and Mn) have been studied by continous and alternating immersion tests in a solution containing 20% H₂SO₄ and 10% FeSO₄ at 40°C. In the as-extruded state the corrosion of monophasic alpha alloys increases with aluminium content. Larger quantities of ß' martensite exercise a negative effect. Addition of 2 weight-% Ni do not improve the corrosion resistance of the alloys with 5 and 8% Al. Cold reduction of alpha alloys give rise to a pronounced intensification of corrosion. No positive effect can be obtained by a thermal treatment of the alloys CuAl 10 Fe 4 Mn Ni and CuAl 10 Fe 4 Ni 5. The corrosion takes place under the following forms: uniform corrosion (CuAl 5), preferred corrosion of grain boundaries (CuAl*, Cual 9, Mn 2 FeNi and CuAl 10 Fe 4 Ni 5 after thermal treatment) and dealuminisation (CuAl 10 Fe 4 Mn 3 Ni). With a view to corrosion resistance the alloys CuAl 5, CuAl8 CuAl 9 Mn and - probably - CuAl 8 Fe seem to be superior to the others.