Inhibierung der Korrosion von Messing 63/37 in Natriumhydroxidlösungen

Inhibition of the corrosion of 63/37 brass in sodium hydroxide solutions 30 substances have been investigated as inhibitors for the corrosion of 63/37 brass in sodium hydroxide solutions. Glucose retards the corrosion completely. Resorcinol, pyrogallol, phloroglucinol, gallocyanine, hydrazine sulfate, afford >90% protection to brass 63/37 in all the alkali concentrations studied. The performance of phenol, catechol, quinone, pyrogallol, α-naphthol, quinalizarin, m-aminophenol, thiourea is also satisfactory >80%. Sodium rhodizonate and tannin are effective in higher concentrations of alkali whereas salicylaldehyde is effective only in 0.2 N sodium hydroxide solution. The performance of acriflavine, acetylacetone and cupron is far from satisfactory.     

Inhibierung der Korrosion von Messing 63/37 in Kaliumpersulfatlösungen

Inhibition of the corrosion of 63/37 brass in potassium persulphate solutions Paraldehyde, furfuraldehyde and salicylaldehyde have been investigated as inhibitors of the corrosion of 63/37 brass in 0.2 M potassium persulphate solutions. Salicylaldehyde has been found to afford >99% protection to brass from 5–90 minutes duration. The efficiency of salicylaldehyde is at its maximum at 4.35 m/l. concentration, further increase in inhibitor concentration induces a decrease in its efficiency which is explained by the fact that at higher inhibitor concentrations, the polarisation of the cathode and the anode is decreased. Furfuraldehyde and salicylaldehyde exercise a predominant action on local cathodes, whereas paraldehyde acts both on local cathodes and anodes.     

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.     

Inhibierung der Korrosion von Messing 70/30 in Natriumhydroxidlösungen

Inhibition of the corrosion of brass 70/30 in sodium hydroxide solutions Tests with brass 70/30 in NaOH (0.2 N, 0.5 N, 1.0 N) with addition of various inhibitors. Among the compounds used as inhibitors, furfural and glucose can be considered as efficient inhibitors under any test condition, while other compounds are characterized by maximum efficiencies at certain optimum concentrations of NaOH or the inhibitor respectively. This case is true e.g. with Na-rhodizonate, Na-chromotrapote and tannine. Other materials studied as inhibitors are: quinalizarine, 2,4-pentanedione, cyclohexanone, thiourea, dithiooxamide, Na-diethyldithiocarbamate, hydrazine sulfate, cupferron, cupron, gallocyanine, acriflavine and posine.     

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.     

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.     

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.     

Wirkung von schwefelhaltigen Inhibitoren auf die Korrosion von Messing 63/37 in Trichloressigsäure

Action of sulphur containing inhibitors on the corrosion of 63/37 brass in trichloroacetic acid Trichloroacetic acid is highly corrosive to brass. Sodium thioglycolate, sodium diethyl dithio carbamate and carbon disulphide have been studied as corrosion inhibitors for brass (63/37) in trichloroacetic acid. The inhibitive power of sulphur-containing organic compounds is due to chelate formation, the chelate adhering strongly to the metal surface. The efficiencies of above stated inhibitors were found in the following order: .     

Anodische Polarisationskurven von Messinglegierungen in Ammoniumchloridlösungen

Anodic polarization curves of brass alloys in ammonium chloride solutions Potentiodynamic investigations have revealed, that curves traced during the low rate polarization characterize the anodic behaviour of brasses. Such curves show that copper-rich alloys behave in a way analogous to that of copper. It is consequently possible from the polarization curves of copper to derive the behaviour of such alloys. Zinc- rich alloys behave like zinc at the beginning but during the dissolution process a new copper-rich phase is probably formed and the behaviour is then comparable to that of copper-rich alloys. Alloys of h&h copper content can be passivated, but passivation current and potential grow as the zinc con- tent is increased.     

Örtliche Korrosion von Komponenten aus Messing MS 58 in der Trinkwasser-Installation

Localized corrosion of yellow brass 58 in tap water installation Yellow brass material with 58 wt.-% Cu is subjected to dezincation and cracking in tap water. Both kinds of corrosion are enhanced by tensile stresses and by anodic polarisation resp. oxygen content of the water. Furthermore, the water type has an effect, where - according to this investigation – the chloride content is of interest. The presence of critical components for SCC (such as NH₃) are not necessary. In the case of mixed installation with tubing of inert material (such as stainless steel or plastics) the corrosion likelihood is increased in comparison to galvanised steel or copper because of oxygen consumption by corrosion of the latter materials. Bimetallic corrosion in mixed installation with stainless steel does not take place. Failures of components of domestic installations by corrosion should be prevented by using a material having a higher resistance to dezincation.     

Einfluß der Zusammensetzung von Messinglegierungen auf die Entzinkung und interkristalline Korrosion in Ammoniumchloridlösung

Influence of the composition of brass on dezincification and intercrystalline corrosion in ammonium chloride solutions The intercrystalline corrosion of As-containing α-brass is not restricted to a defined brass composition but is found also with brass types containing, in addition, AL and Sn. In the case of two-phase alloys of this type the β-phase is preferentially corroded, in Particular when the brass contains As and the β-phase forms a coherent network. On the basis of the results obtained a hypothesis has been derived as to mechanism the partial processes; this hypothesis is confirmed by result obtained with macroelements of As-containing and As-free brass. According to this hypothesis the intercrystalline corrosion of α- brass can be ascribed to the inhibition by As of the dezincification, so that no regions more anodic than grain boundaries are formed. This is why the boundaries are attacked preferentially.     

Inhibierung der Korrosion von Stahl in sauren Medien durch Ammoniumalkylxanthogenate

Inhibition of steel corrosion in acid media by ammonium alkylxanthogenates The authors have investigated the inhibiting effect of ammonium alkylxanthogenates with different alkyl radicals (C₅? C₁₆) and ammonium groups substituted in different ways (alkyl radicals C₁? C₁₀, even with formation of 6-member ring structures with the nitrogen). The acids investigated included inorganic (sulfuric, hydrochloric, amidosulfonic) and organic acids (formic, acetic, lactic, citric). The inhibitors reduce corrosion losses as well as hydrogen absorption during pickling or cleaning of steel. The effect can be attributed not only to the presence of the S and N atoms, but also to the alkyl radicals which probably form some type of hydrophobic barrier on the metal surface. As to the reduction of hydrogen absorption the effect is observed after extended periods of time only, while no essential difference has been found between inhibited and uninhibited acids as to their effect on mechanical properties.     

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.     

Inhibierung der Korrosion von Eisen in Säuren mit Hilfe von organischen Schwefelverbindungen

Inhibition of iron corrosion in acid with the aid of organic sulphur compounds Tests were carried out with Armco-iron in 1 n 10%-aqueous ethanol sulphate with the addition of n-butyl, s-butyl, n-hexyl, n-octyl, n-decyl, benzyl and phenylmercaptane, o- and m-thiokresol. The purpose was to determine the inhibition effect on the loss of weight and on the embrittlement through hydrogen adsorption. The inhibition effect is probably governed by adsorption via a free pair of sulphur electrons. The sulphur charge is therefore the controlling factor which also explains the effect of the chain length which affects the electron density at the sulphur. The inhibition effect has a maximum with C₈ whilst, with larger chains, a screen effect is again apparent. The adsorption of hydrogen is first stimulated by low inhibitor concentrations, and later inhibited. But there is no clear correlation between the effect on corrosion and that on hydrogen adsorption.     

Nicotinsäure als Inhibitor der Korrosion von Aluminium-Magnesium-Legierungen in salzsauren Lösungen

Nicotinic acid as an inhibitor of the corrosion of aluminium-magnesium alloys in hydrochloric solutions Research has been carried out into the inhibiting effect of nicotinic acid on the corrosion of pure aluminium, 98,8 pC Aluminium, Al-Zn and Al-Cu alloys in hydrochloric acid. The inhibitting effect of graduated quantities of nicotinic acid on the solubility in hydrochloric acid of an Al-Mg-Mn alloy as a function of hydrochloric acid concentration and of the duration of the test is discussed in detail A comparison of cathode polarisation and weight loss shows that this alloy can be given effective cathodic protection.     

Korrosion von CuZn-Legierungen in Chloridlösungen bei potentiostatischer Polarisation

The corrosion of CuZn alloys in Chloride solutions with potentiostatic polarisation The intercrystalline corrosion susceptibility of brasses can be studied either by potentiostatic methods in NH₄Cl+HCl solutions with polarisation to +80 mV, or – without polarisation – in NH₄Cl+HCl+CuSO₄ solutions where the potential of +80 mV is attained without external polarisation. Tests carried out with macroelements formed either by brasses having different structures (α, β/α), or identical structure (α) but different zinc contents (21 and 32% respectively) have shown the preferential attack of the β phase at potentials lower than those required for grain boundary dissolution, and the more anodic character of the alloys of higher zinc content.     

Anodisches Verhalten und Korrosion von Titan in methanolischen Lösungen

Anodic behaviour and corrosion of titanium in methanolic solutions The anodic behaviour of titanium in methanolic solutions containing halides or water in various concentrations has been investigated and the result were compared with the result obtained by corrosion tests performed on ?U”? bend specimens in similar solutions. Polarization curves can predict the susceptibility to titanium to stress corrosion cracking as in the case the metal surface is not passivable. These conditions can be obtained in the presence of low water content (i.e. 0.1% H₂O) and of activating ions as Cl^? and Br^? even in very small concentration (10^5?, 10^4? M). Presence of higher water contents and/or of F^? or I^? ions can to some extent produce passivation of the metal surface and cracking does not occur. A lower water amount in the solution (i.e. 130 ppm) eliminates any possibility of passivation of the metal surface, so that cracking can occur even in the absence of chlorides or bromides. High Cl^? concentration in the solution. (i.e. 0.1 M NaCl + 0.1% H₂O) can produce intergranular attack even in the absence of applied stress.     

Zur Korrosion von Silber in Chloridlösungen unter hydrothermalen Bedingungen

The corrosion of silver in chioride chlotions under hydro-thermal conditions The corrosion rate of fine silver in 0.1 and 1 n-HCl, NH₄Cl, LiCl and NaCl solutions has been investigated at temperatures between 300 and 450° C and at pressures between 1000 and 3000 bar. Corrosion took place in all cases, and most markedly in 1 n-HCl solution at higher temperatures. The effect of the electrolyte decreased in the sequence named above. The corrosion process is mainly governed by chemical transport reactions.