Inhibitoren der Korrosion (14). pH-Wert-Änderungen in Suspensionen von Eisen in 0, 2 m NaCl-Lösungen unter den Bedingungen der Sauerstoffkorrosion

Corrosion inhibitors (14) pH variations in suspensions of iron in 0.2 m NaCl solutions under conditions of oxygen corrosion The pH of iron suspensions is deter-mined in a suitable apparatus under varying reaction conditions. The results are as follows:

• 1 In a suspension of 25 grs of carbonyl iron powder in 100 ml of pure water there is no pH variation, neither under nitrogen nor under oxygen.
• 2 When 25 g of carbonyl iron powder are introduced under 100ml 0.2 m NaCl solution, the pH value rises from 6.60 to 9.4-9.5 within three to eight minutes.
• 3 Determination of the dissolved Fe(OH)₂ quantity and conversion of the latter to pH units reveals, that the pH rise is due to (a) an exchange of OH^?-ions for CL^?-ions at the boun.

     

Inhibitoren der Korrosion 21 (1) – Autoxidationsstudien an Fe2+-Salzen der Tetramethylen-1,4-bis-phosphonsäure,der Hexamethylen-1,6-bis-phosphonsäure,der Benzol-1,4-bis-phosphonsäure,der Phosphorsäure und Pyrophosphorsäure als Modell einer die Korrosion des Eisens hemmenden Deckschicht

Corrosion Inhibitors 21 (1) – Investigations into the autoxidation of Fe²⁺ salts of tetramethylene-1,4-bis-, hexamethylene-1,6-bis-, benzene-1,4-bis-phosphonic acids, phosphoric acid and pyrophosphoric acid as a model of a surface layer inhibiting the corrosion of iron The efficiency of organic bisphosphonic acids as inhibitors of the corrosion of iron is due to the fact that Fe²⁺ ions leaving the iron surface react with the acid immediately and give rise to the formation of threedimensional surface layers. The more dense the structure of these layers, the more resistant these network is against oxygen and the more resistant to hydrolysis are the Fe? OP bonds, the better the protective effect. Oxygen as well as chloride ions are then prevented excess to the metal surface. The distribution of phosphorus in the precipitates obtained during the model experiments yields information concerning the degree of crosslinking.     

Inhibitoren der Korrosion 17(1) Die Bedeutung des „Hart-Weich-Konzepts”︁ von Pearson für die Erkennung von Struktur-Wirkungsbeziehungen von Inhibitoren bei der Korrosion des Eisens in NaCl-Lösungen bei Gegenwart von Sauerstoff

Corrosion inhibitors 17 The importance of pearson's “hard-soft-concept” with respect to the recongnition of relationship between structure and activity of inhibitors of the corrosion of iron in sodium chloride solutions in the presence of oxygen On the base of a previously published postulate according to which Pearson's hard-soft-concept may form the base for finding inhibitors for specific applications it is shown with the aid of model inhibitors with “hard” functional groups that it is indeed feasible to derive defined relations between the structure and the activity of inhibitors. The hard groups used were the phosphoryl ?P(O)O and the carbonyl ?C?O groups. It has been shown that such compounds are able to form very stable and protective surface layers on iron and that the efficiency of the inhibitors clearly increases with increasing length of the aliphatic chain. As has been shown by eletrochemical measurements these acids have a bearing on the rest potential as well as on the current-potential behaviour; this fact points to rather variable compositions of the surface layer. In the case of polyfunctional acids sterical factors may have a bearing on inhibitor efficiency, too.     

Inhibitoren der Korrosion (9) Nachweis der Sekundärinhibitoren bei einigen Sulfoxiden,Triphenylarsinoxid und einigen Sulfoniumsalzen

Demonstration of secondary inhibitors of some sulfoxides, triphenyl arsene oxide and some sulfonium salts The inhibition values of some dibenzyl sulfoxide and structurally related com-pounds, and of triphenyl ursine oxide are determined. Sulfoxides and ursine oxides are (a) displaced, after protona-tion, into the cathodic regions and (b) converted, after electron acception, into secondary inhibitors which are liable to coordination (thioethers and tertarsines). The secondary inhibitors are either ad-sorbed by the metal and then suppress the dissolution of iron, or they are not fixed on the metal (e. g. diphenyl sul-fide) and have no protective action in that case. In the case Of dibenzyl sulf- oxide about 90% of the compound can be obtained by dissolution from the iron surface as dibenzyl sulfide, while the solution still contains 16% of non-converted dibenzyl sulfoxide. In the be found on the iron surface as tri-phenyl arsine, the rest is in solution as protonated triphenyl ursine oxide. From case of triphenyl ursine oxide 70% can the four sulfonium salts studied, only tribenzyl sulfonium hydrogen sulfate is subject to reduction to any greater ex-tent, the three other sulfonium salts can be isolated from the testmedium up to 90% without having undergone a transformation. Diphenyl allyl salfo-nium tetrafluoborate yields in the test medium, as the result of a reductive de-composition, 1 to 2% of a propenepro-pane mixture.     

Sulfurierte Fettsäurederivate als Inhibitoren der Stahlkorrosion in Elementarschwefel,Schwefelwasserstoff und Chloride enthaltenden Systemen

Sulfurated fatty-acid derivatives as inhibitors of steel-corrosion in systems containing elementary sulfur, hydrogen sulfide and chloride It was shown experimentally in agents containing elementary sulfur, hydrogen sulfide, and chloride, that the corrosion of steel can be strongly prevented through the interaction of the following factors: (a) the presence of a polysulfidic organic compound with intramolecular sulfur-chains of at least three sulfur atoms, (b) the presence of an unsaturated organic coumpound, and (c) the presence of a nitrogen-containing compound. These nitrogen-compounds activated elementary sulfur (S₈) or long-chained polysulfides to nucleophilic and/or radical fragments by splitting the ring arrangement or the polysulfidic chain, respectively. The fragments seem to be able to react with multiple carbon bonds and metal-sulfur bonds and develop surface coating protective films.     

Inhibitoren der Korrosion 10 (1). Nachweis der Sekundärinhibition durch Allyl-triphenyl-phosphonium- bzw. arsoniumbromid und N-Allyl-chinaldiniumbromid

Corrosion inhibitors (10) Demonstration of the secondary inhibition by allyl triphenyl phosphonium and arsonium bromides and N-ally1 quinaldinium bromide Triphenyl allyl phosphonium (1) and arsonium (2) salts as well as allyl quinaldinium bromide (4) are corrosion inhibitors of moderate efficiency. In acid media they are reduced by carfinyl iron powder to yield triphenyl phosphine and triphenyl arsine respectively and quinaldine. The two products mentioned the first form a layer on carbonyl iron and, after extraction, may be identified by gas chromatography. The allyl group is eliminated by iron from 1, 2 and 4, yielding Pro-pene, propane and, probably, cyclopropane. The hydrocarbon quantities determined by gas chromatography are in good agreement with the values found in the gravimetric determination of allyl-onium salts after the reaction. Ally triphenyl phosphonium bromide ( I ) and allyl diphenyl sulfonium tetraborate (3) yield propene and propane in a 1:1 ratio. In the case of (2) and (4) this ratio is shifted to 14:l and 7:l respectively. The hydrocarbon proportion in the gas mix-ture is higher at the beginning of the reaction than toward its end; at the beginning, the Propane:propene ratio is also displaced, the formation of propane having priority.     

Inhibitoren der Korrosion (12). Nachweis der Bildung von Sekundärinhibitoren mit Hilfe der „Spezifischen Keim-Methode”︁ von Karagounis

Identification, by the “specific nucleus method according to Karagounis”, of the formation of secondary inhibitors Various onium salts having good inhibiting properties are reduced on the surface of iron in acid solutions. The secondary products formed during this reaction are good inhibitors themselves and form thin layers on the metal surface. These layers on have various thicknesses: dibenzyl sulfoxide forms up to 20 molecular layers within a very short period of time, while some quaternary phosphonium salts form only one to two molecular layers in 24 hours. The surface coverage is not homogeneous during the initial period. The specific crystal nucleus method by Karagounis which has been used in this study confirms the analytical results.     

Inhibition der Korrosion 15 (1) Über die Wirkungsweise von Korrosionsinhibitoren des Eisens in Säuren sowie in NaCl-Lösungen bei Gegenwart von Sauerstoffen

Corrosion inhibitors(15) Mode of action of inhibitors of the corrosion of iron in acids and in NaCl solutions in the presence of oxygen A review is given of electrochemical and other methods which may be used for studying the mechanism of corrosion inhibition. Non-electrochemical methods include UV and IR reflexion spectroscopy, extinction of fluorescence by amines, ellipsometry, electron microscopy and X-ray methods. Chemical methods involve direct analysis of the protective surface layers, electron microprobe analysis and the Warburg method. As to inhibition mechanism as such examples are given to show the effect of structural parameters, the importance of bonding and electron bonding, the effect of reaction resulting in the formation of product able to act as secondary inhibitors (in the context, emphasis is placed on onium compounds, sulfoxides). Finally, data are presented concerning the inhibitor effect of some technical surface active compounds, glycin and sarcosin derivatives, aromatic carboxylic acids and organic phosphonic acids.     

Phosphor in Eisen und Stahl – Ein Überblick über grenzflächenanalytische Untersuchungen am Max-Planck-Institut für Eisenforschung zum Segregationsverhalten des Phosphors an äußeren und inneren Grenzflächen von Eisen und Stahl

Phosphorus in iron and steel – An overview of surface analytical investigations of the segregation behaviour of phosphorus on internal and external iron and steel surfaces The surface segregation of phosphorus was studied on (100) oriented single crystals of the type Fe? P and Fe? Si-P. Phosphorus shows a strong tendency to enrich at surfaces. The interaction with lattice defects leads to an additional enrichment below the surface. A strong repulsive interaction of phosphorus with segregating silicon can lead to a complete displacement of silicon from the surface region. Equilibrium segregation experiments revealed a segregation enthalpy for phosphorus of ?180 kJ/mol for the ternary system Fe? Si? P, this is only slightly lower than the segregation enthalpy of the extremely surface active sulfur in iron anti steel. The strong tendency of phosphorus to enrich at interface in iron and steel is also observed for grain boundaries. The grain boundary segregation of phosphorus was studied for the systems Fe? P, FeC? P, Fe? M? P and Fe? M? C? P with M ? Cr, Mo, V, Ti, Nb. The segregation of carbon leads to the displacement of phosphorus. By the presence of carbide forming elements like chromium in the material this positive effect is reduced. Elements, that can tie up phosphorus, like titanium and intermetallic phases, that dissolve phosphorus, -an also reduce the segregation of phosphorus. addition ally a phosphorus segregation to the interface carbide/matrix was observed.     

Inhibitoren der Korrosion (8) Über die Abhängigkeit der Korrosionsinhibierung des Eisens in Salzsäure von der Struktur quartärer Phosphoniumsalze

Inhibition of the corrosion of iron in hydrochlorid acid as a function of the structure of quaternary phosphonium salts In the case of quaternary phospho-nium salts there is no direct relation between their inhibiting power in deaer-ated acid media and the polarographi-cally determined reduction potentials. The inhibiting effect can in a first line be attributed to sterical factors con-nected with the fragments formed after incorporation of two electrons and be-coming fixed to the iron surface. Biphosphonium salts having saturated or unsaturated bridges are excellent in-hibitors under the conditions mentioned. Most efficient are biphosphonium salts having chaines of 4 to 10 methylene groups between the phosphonium cen-tres. The rigid p-phenylene radikal is less suitable as a linking principle. Phe-nyl phosphine and diphenyl phosphine in low concentrations accelerate corro-sion and exhibit a protective effect only in higher concentrations. Polymers having incorporated phos-phonium centres are only moderate inhibitors when compared to biphospho-nium salts. The synthesis is outlined and some physical and chemical properties are given.     

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.     

Inhibitoren der Korrosion 31 (1). Beitrag zur Inhibierung der Korrosion von Zink und Messing

Inhibitors of corrosion 31 (1). Contribution to the inhibition of the corrosion of zinc and brass The following compounds approved as inhibitors of the corrosion of copper are investigated as inhibitors of the corrosion of zinc and brass: 2-aminopyrimidine (A), 5-aminotetrazole monohydrate (B), benzotriazole (C), Kupferron (D), 2-mercaptopyrimidine (E), 2-mercaptothiazoline (F), 2-methyl-4-amino-5-cyanopyrimidine (G), tetrazine-B (H) and 2-amino-3,4,1-dithiazoline-1,5, thione (I). In the presence of the compounds A, B, C, E and G zinc plates are totally corroded in 15 days using standard conditions. With the compounds D, F and H the protective values are 29%, 14% and 39%. A more differentiated information is obtained with acid consumption-time-curves at constant pH using zinc powder. Only the compound C slows down the corrosion. The other compounds enhance the corrosion. In corrosion studies with mixtures of copper and zinc powders the compounds B–I inhibit the corrosion of copper. The acceleration of the corrosion in the presence of compound A was investigated. The corrosion of brass (plate, grain, powder) proceeds with primary removal of zinc. The compounds A, E, F and H are good inhibitors. The inhibition values for brass 64/36 are better than for brass 90/10. The composition of the protecting layers produced on the surface of brass in the presence of the organic inhibitors is determined by X-ray fluorescence measurements. With the inhibitors A, B, E, F and G the content of copper is over 90%, but 80% in the presence of the inhibitors C and H, which delay also the corrosion of zinc. The conception of primary loss of zinc and the subsequent production of a copper-rich copper-inhibitor-protection-layer is confirmed by determining the composition of the precipitations and of the solutions produced during the corrosion of brass.     

Studies on the effect of pyranocoumarin derivatives on the corrosion of iron in 0.5 M HCl

The effect of some new synthesized pyranocoumarins on the corrosion of iron in 0.5 M HCl was investigated. The investigation involved electrochemical polarization methods (potentiodynamic, Tafel extrapolation and the determination of the polarization resistance) as well as weight loss measurements. The results show that these compounds act as mixed type inhibitors, but the cathode is more preferentially polarized. The inhibition efficiency depends on both the nature and concentrations of the investigated compounds. Compounds are found to adsorb on the iron surface according to the Langmuir adsorption isotherm. Fourier transform infrared spectrophotometry was used to obtain information on bonding mechanism between the metallic surface and the inhibitors.     

Mößbauer- und ESCA-Untersuchungen zur Bildung oxidischer Eisenphasen in wäßrigen Medien unter der Einwirkung organischer Korrosionsinhibitoren

Mössbauer and ESCA investigations on the formation of oxidic iron phases in aqueous solution under the influence of organic corrosion inhibitors Corrosion layers on steel grown in water of well defined hardness and chloride concentration were studied by Mossbauer and ESCA spectroscopy with particular emphasis on the influence of added organic inhibitors. Relatively thick layers were found with an unexpectedly small iron content (as FeOOH). The layers contain a remarkable amount of constituent ions from the solution and fragments of the inhibitors. The latter seem to be decomposed by the corrosive medium: It is assumed that the whole organic molecule determines the kind of transportation of the inhibitor to the iron metal, but that the inhibition itself is due to functional groups only.     

硅烷偶联剂对羰基铁粉电磁性能的影响

利用FT-IR,SEM和矢量网络分析仪等对羰基铁粉改性前后的化学键特性、微观形貌和电磁参数等进行了研究,实验结果表明:硅烷偶联荆在羰基铁粉表面形成不均匀包覆层;羰基铁粉的电磁参数随硅烷偶联剂用量的增加而变化;根据电磁参数对材料的吸波性能进行计算,当乙烯基三甲氧基硅烷用量为2.0%(质量分数,后同)时,得到的吸波效果最好,5.2～10.0 GHz反射率均小于-10 dB.     

Inhibitory effect of cysteine in acid media

The new data and the data available in the literature on the use of the processes of complex formation for protection of metals against corrosion are analyzed. Using the example of cysteine, we show the applicability of the conception according to which the protective effect of some organic inhibitors is due to the formation of partially soluble compounds on the metal surface between these substances and the cations of a dissolving metal. It is shown that, using the proposed conception, it is possible to explain the features of the electrochemical and corrosion behavior of iron in cysteine-containing solutions of sulfuric acid. The approach under discussion and the recommended criteria make it possible to carry out a focused selection of corrosion inhibitors.     

Anwendung der Elektronenmikrosonde zur Untersuchung des Einflusses der Oberflächenvorbehandlung auf den Verlauf der Phosphatierung und der elektrophoretischen Beschichtung

Application of the electron microprobe to the investigation of the influence of surface pretreatment on the progress of phosphatation and electrophoretic coating A general discussion is presented of the possibilities available for analyzing micro regions on solids with the aid of the microprobe. Along the same lines a survey is presented concerning the range of applications of this method of analysis in connection with the chemical pre-treatment processes of metal Surfaces. The principle of action of the electron microprobe, the method of analysis and the specimen preparation are dealt with. It is shown, that the electron microprobe is a useful means for studying the influence of pretreatments on the structure and formation of phosphate and organic coatings. In the case of the analysis Of the phosphating process, however, the can be interpreted more easily when supplemented by results of X-ray structural analysis. The distribution of Fe, P, Mn, Zn and Ni across the section of the coating has been determined and a hypothetical mechanism of phosphating has been formulated thereupon; the ac-of Ni²+ ions has been explained as well. It has been shown, that components of the substrate as well as of the coating are dissolved during the electrocoating process and are incorporated in the organic coating. This process has a great importance with respect to colour and protective properties of the coatings and with respect to the turn-over of the electrolyte.     

Combined Inhibitors of Acid Corrosion of Iron: Dependences of Their Protective Effects on the Concentration

In continuation of the previous investigations [1, 2] devoted to combined inhibitors of acid corrosion of iron, the protective effects of mixtures of halides with some organic compounds and the mutual influence of their components were determined. Variations of the relevant parameters with the concentration were also studied.     

Untersuchungen zur passivierenden Wirkung organischer Oxydationsmittel auf Eisen in neutralen und schwach sauren Lösungen. 2. Mitteilung: Aromatische Nitroverbindungen

Investigation into the passivation effect of organic oxidizing agents on the corrosion of iron in neutral weakly acid solutions. 2nd communication: Aromatic nitrocompounds The present communication is con cerned with the corrosion inhibiting properties of aromatic nitro compounds on iron in the neutral range. Nitrobenzenes (m-nitroaniline, p-chloronitrobenzene, M-nitrobenzoic acid, ethylester, p-nitrobenzaldehyde, p-nitrobenzonitrile) in concentrations between 0,25 · 10^?2 and 0.5 · 1^?2 Mole/litre act as stimulators in airsaturated 20% methanol of pH 6.8. Their combination with a 20% methanolic boric acid/borate solution of pH 6.8 – which, as such, only maintains passivity, yields passivating systems. From these examples as well as from others involving known inhibitors it appears highly probable that the prassivation of iron by corrosion inhibiting addition in the neutral range, too, requires a communication of oxidizing and non-oxidizing agents (combination principle )able to lower the critical passivation current density.     

Inhibitoren der Korrosion (11). Nachweis der auf Eisengrenzflächen gebildeten Sekundärinhibitoren durch UV-Absorptions- und Fluoreszenzspektroskopie

Identification, by UV absorption and fluorescence spectroscopy, of the secondary inhibitors formed on iron boundary faces In acid solution, triphenyl benzylphosphonium chloride forms a layer on an iron surface; this layer should, according to the results of UV reflexion spectroscopy, be identical with triphenyl phosphine. The mono- and bis-phosphonium salts, too, are degraded by reduction at the iron boundary surface; the anthracene derivatives formed by this reaction are identified by the same method; they turn out to be methyl anthracene. A further separation of the reaction products has been attempted by thin layer chromatography (investigation of the extracts in cyclohexanol and methanol) yields no clearly distinguishable fluorescence spectra.