Zur Elektrodenkinetik von Reinst – Eisen im Phosphatelektrolyten bei Feststoffeinschlag (Simulation von Erosionskorrosion)

Electrode kinetics of high purity iron in phosphate electrolytes under solid particle impact (Simulation of erosion corrosion) Erosion-corrosion of high purity iron was simulated by means of a vibration cell in a neutral phosphate electrolyte. The investigations were carried out to explain the initiation processes of this type of corrosion. The results confirm the general conception of the central role of reaction layer destruction in erosion-corrosion processes. Under these conditions a qualitative change in reaction layer formation occur. By solid impact the layers are destroyed locally and so conditions of pit nucleation exist. The destruction of the layers depends on the action of shear forces resulting from tensile or compressive strains.     

Zur Kinetik der Sauerstoffreduktion bei der Korrosion von Nickel in sauerstoffhaltiger Schwefelsäure

Kinetics of oxygen reduction during the corrosion of nickel in oxygen containing sulfuric acid The rate of oxygen reduction was determined for the corrosion of nickel in sulphuric acid containing oxygen. The rate depends upon the oxygen concentration and the acidity of the electrolyte. For a second order reaction with a preceding diffusion of oxygen and protons the values of the rate constant and the thickness of the diffusion layer were calculated. It could be shown that in In sulphuric acid the reduction rate is control led by the oxygen diffusion while in the weaker acids the rate controlling step is a proton transfer to the oxygen, adsorbed at the metal surface. Measurements of the dependance of the corrosion in In sulphuric and hydrochloride acid confirm these results.     

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.     

Kinetik der Lochfraßkorrosion bei konstantem Potential

Kinetics of the pitting corrosion at constant potential Measurements of the depth and diameter of corrosion pits on nickel and 18Cr-12Ni-2Mo steel were performed. It was found that the exponent b in equation i ～ t^b depends upon the Cl^?/SO₄^2? ratio in the electrolyte. Kinetics of the pit growth at constant potential is discussed, and models for the development of Pits in shape of caps and cylinders are given. Experimental results fit in with those models.     

Kinetik und Mechanismus der Hochtemperaturschwefelung von Silber

Kinetics and mechanism of high temperature sulfidation of silver The formation of the compact sulfide scale on silver follows a parabolic law, the diffusion of silver ions in the reaction product being the rate controlling step. During this scaling reaction it is not necessary to meet all the requirements situated by Wagner's theory: in the silver/sulfur system e.g. the difference of chemical potentials at low temperatures is below the values which would be required according to Wagner's theory. The calculation of the self diffusion coefficients of the metal or the oxidant from oxidation kinetics does not yield sensible results unless — what must be shown by preliminary experiments — thermodynamical equilibria exit on either phase boundary of the scale. Contrary to existing opinion the parabolic nature of the formation of a compact one-phase scale layer does not constitute a sufficient criterion.     

Zur Bildung des kubischen Fe3S4 bei der Korrosion von Stahl

The formation of cubic Fe₃S₄ during the corrosion of steel In hydrogen sulfide saturated water Fe₃S₄ (Greigite) is formed cathodically, as soon as the pH changes from the basic to the acid region. The presence of this compound thus enables the conclusion to be made that the action of hydrogen sulfide on iron has taken place under acid conditions.     

Kinetik der mit Wasserstoff- bzw. Sauerstoffdepolarisation verlaufenden Korrosion von Eisen

Kinetics of the corrosion of iron accompained by hydrogen or oxygen depolarisation The paper brings a critical review of research work devoted to the problem of corrosion of iron in aqueous solutions, free from oxygen as well as aerated. The relationship is discussed between corrosion rate on the one hand, on the other hand, the p_H value, the composition of the solution, the admixtures contained in the iron, the structure of the latter, and the condition of the surface of the test specimens. As regards corrosion associated with oxygen depolarisation, the paper also deals with the transport problems. The authors emphasize that the results obtained by different methods are liable to differ from each other.     

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.     

Die Kinetik des Rostens von Eisen in der Atmosphäre

The kinetics of the rusting of iron at the atmosphere Laboratory experiments organized to describe the kinetics of active periods of atmospheric rusting have lead to the following conclusions: At temperatures ? 0°C the corrosion velocity is independent from the SO₂- content and humidity of the atmosphere. Above 0°C the corrosion rate is controlled by reactions leading to sulphate-nests and to the hydrolytic rust-formation. Simultaneous action of high temperature (≥15°C) and higher amounts of water (≥100 g.m^?2) decreases the accelerating effect of growing SO₂-contents. The corrosion belocities found are in good agreement with data calculated from long-term tests in natural environments.     

Thermodynamische Bezugsspannungen bei der Selbstpassivierung von Titan

Thermodynamic reference potentials with the self-passivation of titanium In the p_H range from 0 to 14, titanium in aqueous electrolytes shows, like uranium, zirconium and niobium, either passive or active behaviour. In this range, there is no transpassivity. On passive titanium in acid or alkaline solutions, the double cover layer electrode Ti/TiO₃/TiO₃ is formed which is stable on active and passive titanium.     

Die chemischen Gleichgewichte bei der Inchromierung von Stahl

The chemical equilibria encountered with the chromium-plating of steel In order to determine the equilibrium conditions, the authors investigated, in the compound system Fe(s) + CrJ₂(g) ? Cr(s) + FeJ₂(g) used for diffusion-type chromium plating, the two stages Cr(s)+ 2J(g) ? CrJ₂(g) and Fe(s) + 2J(g) ? FeJ₂(g) which determine the reaction rate. The former stage was investigated at a temperature range of 700 to 1160° C, the latter at 760 to 1080° C. In this temperature range, the equilibrium is shifted somewhat to the left, the shift increasing with higher temperatures. However, as the general correlation of the equilibrium constants with temperature is low, it may be assumed that chromium-plating could be carried out over a much wider temperature range than is usual at present.     

Die Rolle der Begleitstoffe von Abgaskondensaten aus der Erdgasverbrennung bei der Korrosion von Wärmetauschern

Impurity constituents of flue gas condensates and their significance for the corrosion of heat exchangers This paper presents investigations concerning the acidic constituents of flue gas condensates which may be generated by the combustion of natural gas. Nature, origin and concentration of relevant constituents will be presented. Their corrosive impact on components of domestic heating facilities will be discussed taking into consideration usual materials based on aluminium, stainless steel and copper. It will be shown that condensates are considered as diluted and aerated acids with a moderately reduced pH. With respect to aluminium based alloys and stainless steels the corrosive potential of condensates is deduced from their content of strong acids. When condensing is forced due to techniques which are used in condensing boilers there is an effect of dilution active which results in a reduction of the corrosiveness. The primary corrosion mechanism of copper is related to the presence of oxygen in the condensate. Therefore the dilution of condensates is of restricted significance. Unprotected copper is known to be unsuitable for condensing conditions.     

Inhibitoren der Korrosion 7 (1) Nachweis gemeinsamer Wirkungsprinzipien bei der Inhibierung der Säurekorrosion von Eisen,Zink, Aluminium (und Raney-Nickel)

Identification of mechanisms common to the inhibition of the acid corrosion of iron, zinc, aluminium (and Raney nickel) The dissolution of powder and chips of the above metals in diluted and deaerated hydrochloric acid is well inhibited by dibenzyl sulfoxide, benzyl quinolinium bromide and diphenylphosphonium chloride; triphenyl arsine chloride and tribenzylsulfonium hydrogen sulfate are less effective, while diphenyldithiophosphinic acid, thiourea, O-tolyl thiourea and mercaptobenzthiazol in low concentrations act as accelerators.     

Berücksichtigung der Korrosion bei der Konstruktiven Gestaltung von Chemieapparaten

Taking account of corrosion in the design of chemical apparatus The selection of materials is of prime importance in the design of chemical plant because it is necessary to take account, in addition to mechanical stresses, of corrosive influences, in particular where local corrosive attack is to be expected. When using dissimilar metals suitable measures must be taken to prevent contact corrosion. The design must be free from crevices as far as possible in order to avoid crevice corrosion. This requirement must be given due consideration in connection with weld design, too. Discharge devices must enable the plant to be completely emptied in order to prevent shutdown corrosion. Flow velocities must be limited in order to prevent any intensification of corrosion by turbulence, or to avoid erosion corrosion. Simultaneous mechanical stresses and corrosive attack must be taken account of at the design stage in order to prevent stress corrosion cracking and corrosion fatigue. suitable countermeasures include reduction of stress levels, avoiding stress peaks, mitigation of corrosive effects, utilization of more resistant materials, making use of suitable thermal treatments and using protective coatings. Feasible anti-corrosion design ist demonstrated on some construction details.     

Inhibitoren der Korrosion 25(1) – Über die Rolle der Kationen in Neutralsalzen bei der Korrosion von Eisenwerkstoffen in Gegenwart von Sauerstoff

Corrosion inhibitors 25(1) – The role of the cation in a neutral salt in the corrosion of iron in the presence of oxygen The rate of uptake of oxygen, under standard conditions, in the corrosion of 500 mg DAB6 iron powder is dependent on the nature of the cation in a neutral salt (chloride). In the presence of alkali, quaternary ammonium, quaternary phosphonium and alkali-earth chlorides, the rate of oxygen uptake is comparable. With zinc, cadmium, nickel and cobalt chlorides a marked decrease in the oxygen uptake is observed between pH5 and pH7. This is probably due to a block in the cathodic area in the iron boundary layer through precipitation of the rather insoluble basic hydroxides of zinc, cadmium, nickel and cobalt.     

Die Kinetik der Auflösung von Aluminium in alkalischen Lösungen

The kinetics of the dissolution of aluminium in alcaline solutions The stationary dissolution rates of rotating aluminium discs were measured in alcaline sodium sulfate solutions as function of the Ph- value and of the rotational speed using the Förster eddy current test and electrochemical methods. The rates are controlled by diffusion or by heterogeneous dissolution of aluminate from the passive, oxide-covered aluminium. If the rate is diffusion-controlled, a secondary layer very probably consisting of hydrargillite is formed on the passive aluminium. The rate of the heterogeneous dissolution grows little with the Ph-value and depends strongly upon the electrode potential at unnoble potentials and weakly at noble potentials. Cathodic evolution of hydrogen increases the diffusion-limited as well as the reaction limited dissolution rates because of the excess of hydroxyl ions formed at the surface.     

Einfluß der chemischen Zusammensetzung auf die Kinetik der atmosphärischen Korrosion von Stählen

The influence of the chemical composition on the kinetics of the atmospheric corrosion of steel A total of 19 different structural steels were exposed to urban, rural and industrial atmospheres for periods up to three years. The evaluation of the weight losses determind at certain intervals permitted the establishment of a linear relationship which can be used for assessing, within certain limits of concentration, the influence of specific alloying elements. The tests showed that the effects of the different alloys varies with the type of atmosphere and with the degree of corrosion, and may well shift from “favourable” to “detrimental”. The results are also influenced by the quantitative ratios of certain components. The corrosion behavior of the steels is consistently governed by P, S and Cu and, to a lesser extent, by C and Mn.     

Inhibitoren der Korrosion 24 (1) – Zur Vergleichbarkeit der Abhängigkeit der Korrosion und Korrosionsinhibierung von der Chloridionen- und Inhibitorkonzentration am Beispiel von DAB6-Eisen und 1405-Stahl (auch phosphatiert)

Comparability of the dependence of corrosion and corrosion inhibition on chloride ion and inhibition on chloride ion and inhibitor concentration on the example of pure iron and steel 1405 (also phosphated) The rates of uptake of O₂ under standard conditions were measured for iron powder shaken with and without added inhibitor in dependence on the amount of iron and the chloride ion concentration. The results show that the standard procedure used allows a trustworthy measure of the inhibitor efficiency to be drawn from the observed effect. The relationship between the results for DAB 6 iron powder with 1405 steel plates was confirmed by experiments performed on filings from the plates. The rate of corrosion of phosphatized 1405 steel plate is efficiently suppressed by inhibitors with phosphonic acid groups. A treatment of the unphosphatized steel plates with phosphonic acid containing inhibitors in an analogous manner to phosphatizing leads to unsatisfactory results. The conclusion was drawn that the pH value of the inhibitor at the surface layer is important for the attainment of optimal effect.     

Eigenschaften von Elektrolyt-Filmen bei der atmosphärischen Korrosion

Properties of electrolyte films formed through atmospheric corrosion An investigation has been carried out into the composition of the electrolyte films which are formed on non-metallic materials (glass) as well as on metals (Cu, Zn, Fe) in an atmosphere containing SO₂. Fresh as well as pre-corroded specimen were used. It was found that the SO₂ absorbed in the solution is very rapidly oxidized into SO if the electrolyte film contains dissolved particles of the corrosion products. With 1 to 55 ppm SO₂ in the atmosphere, the change in the pH value of the electrolyte is but small and does not vary with the SO₂ partial pressure.     

Inhibitoren der Korrosion 23 (1) – Gibt es eine Struktur- Wirkungs-Beziehung bei organischen Inhibitoren der Korrosion von Aluminium?

Corrosion inhibitors 23 (1) – Does there exist a structure-efficiency relation in the organic inhibitors of aluminium corrosion? Over 400 organic compounds have been routinely tested as potential inhibitors for the corrosion and dissolution of aluminium in In HCl/2,5% NaCl solution, using 10^?2 m/l as the concentration of the organic compound being tested. It was attempted to derive a relationship between efficiency of the inhibitor with molecular structure. Particular attention was devoted to the following classes of compound: organoarsenic; phosphonic and phosphinic acids; aromatic aldehydes and ketones; aromatic and aliphatic carboxylic acids; dihydric phenols; tetrazolium salts and formazan compounds; sulphoxides and aromatic sulphonic acids; sulphonamides and sulphones. For a selected number if inhibitors, the dependence of concentration and the effect of an oxygen-containing atmosphere were studied. Compounds which show good inhibition in the corrosion of aluminium are consistently even better in the protection of zinc surfaces. The mechanism of the corrosion inhibition is not clear, but the results suggest that the total molecular structure of the inhibitor must be considered, with particular importance paid to the nature and the spatial relationship of the different functional groups.