Säureinhibitoren. II. Einfluß von quartären Ammoniumsalzen auf die Wasserstoffaufnahme von unlegiertem Stahl in H2S-freier und H2S-gesättigter Salzsäure

Acid inhibitors. II. Influence of quarternary ammonium salts on the hydrogen absorption of mild steel in H₂S-free and H₂S-saturated hydrochloric acid The influence of organic ammonium salts (pyridine hydrochloride and its derivates, trialkylbenzylammonium halides, pyridines, quinolinium and isoquinolinium compounds quaternarized with benzyl halides and substituted benzyl chlorides) on the hydrogen absorption of mild steel treated with H₂S-free and H₂S-saturated 16% hydrochloric acid at 25 °C was studied using electrochemically controlled hydrogen permeation measurements. Investigations on structure-efficiency correlations revealed that the inhibitors can influence the kinetics of the hydrogen absorption and the rate of metal dissolution with significantly different efficiency. Describing the efficiency profil of acid inhibitors it is therefore necessary to test inhibitors in both respects. This is valid especially in the presence of H₂S which can change the efficiency of inhibitors fundamentally. Besides by structural and electronic variations in the organic molecule the efficiency of the inhibitors tested was influenced by the type of anion (e.g. bromide, iodide). With benzylquinolinium chloride the best results were found in both H₂S-free and H₂S-saturated acid.     

Säureinhibitoren. III. Einfluß von quartären Ammoniumsalzen auf die Wasserstoffaufnahme von unlegiertem Stahl in H2S-freier und H2S-gesättigter Ameisensäure

Acid inhibitors. II. Influence of quarternary ammonium salts on the hydrogen absorption of mild steel in H₂S-free and H₂S-saturated formic acid The influence of quaternary ammonium compounds (benzylpyridinium chloride, benzylquinolinium halides, p-dodecylbenzylquinolinium chloride, benzylisoquinolinium chloride, tri-n-butylbenzylammonium halides, benzyldabcolinium chloride) on the rate of metal dissolution and absorption of corrosion hydrogen in the metal was studied at mild steel in chloride containing 10% formic acid at 25 °C in the presence and absence of H₂S. Generally the same effects were observed like in the system steel/hydrochloric acid. Depending on the kind of inhibitor the presence of H₂S increased or decreased the efficiency of inhibitors to block the H-absorption. Regardless of the presence of H₂S p-dodecylbenzylquinolinium chloride and benzylquinolinium iodide exhibited the best efficiencies in decreasing the rate of metal dissolution and inhibiting the H-absorption in the metal.     

The influence of long term use of inhibitors in hydrochloric acid pickling baths on hydrogen induced stress corrosion cracking

The influence of commercially available inhibitors on the absorption of hydrogen by steel (St 52, StE 460, StE 690, 42CrMo4) in 15% hydrochloric acid was studied. The pickling bath aged continuously due to the chemical reaction with oxidized steel sheets. The H⁺‐ and inhibitor concentration decreased with time. The influence of this ageing process on hydrogen‐induced stress corrosion cracking was tested by in‐situ tensile tests in the bath solution. With increasing ageing of the bath, the reduction in fracture area was reduced and approached the values measured for non‐inhibited acid baths. Furthermore hydrogen permeation was investigated. Permeation current densities rose with increasing ageing of the pickling solution.     

Untersuchungen zum Korrosionsmechanismus von unlegiertem Stahl in sauerstofffreien Kohlensäurelösungen. Teil I. Kinetik der Wasserstoffabscheidung

Investigations into the corrosion mechanism of unalloyed steel in oxygen-free carbonic acid solutions. Part I – Kinetics of hydrogen evolution Polarisation measurements with rotating disc electrodes showed that the corrosion of mild steel in ogygen-free carbon dioxide solutions is not limited by transport processes but is controlled by cathodic activation polarisation. The reason, why oxygen-free carbon dioxide solutions are more corrosive than diluted solutions of mineral acids at the same pH, is explained by the findings that the cathodic reaction is controled by the reduction of both hydrogen ion and adsorbed undissociated carbonic acid, thus stimulating the Volmer-reaction. Electrochemical hydrogen permeation measurements showed that in carbon dioxide solutions the uptake of hydrogen in mild steel is approximately twice as high as in comparable sulfuric acid solutions. Considering the results of comparing experiments with carbon monoxide the possibility of hydrogen embrittlement of mild steel in condensates under high partial pressure of carbon dioxide must be taken into account.     

Carbonyl compounds as corrosion inhibitors for mild steel in HCl solutions

The paper gives an account of the performance of a number of carbonyl compounds as corrosion inhibitors of mild steel in 1–6 N solutions of hydrochloric acid. Furfuraldehyde seems to be the best inhibitor of all the carbonyl compounds investigated. Activation energies in the presence and absence of inhibitors have been evaluated. In cathodic protection studies furfuraldehyde reduces the protective current density considerably. The difference effect is positive in the absence and presence of inhibitors. Galvanostatic polarization data indicate that all these compounds are predominantly cathodic inhibitors. These substances are more effective in preventing the corrosion of aluminium alloys in hydrochloric acid solutions than the corrosion of mild steel.     

Inhibitoren der Korrosion 22 (1) — Einfluß von pH,Sauerstoff, Fremdionen,Art und Konzentration von Säuren auf den Korrosionsverlauf von Aluminium

Corrosion inhibitors 22 (1) – Influence of pH, oxygen, added ions, type and concentration of acids on the corrosion of aluminium Corrosion of aluminium in the presence of oxygen is practically independent from the pH and proceeds with oxygen consumption and hydrogen evolution. This behaviour is found in a solution of acetate buffer with sodium chloride as well as in inorganic (nitric, sulfuric, phosphoric, hydrochloric) acids as in organic acids. In the case of the latter the results are not as clear; in acetic acid the corrosion rate is not influenced by sodium chloride and the same applies to formic acid. While oxalic acid gives rise to hydrogen evolution in the presence of sodium chloride only and citric acid does not give rise to any hydrogen evolution. The solution which appears to be optimum for testing organic inhibitors of aluminium corrosion is unaqueous 1 N hydrochloric acid solution with 2.5% sodium chloride under nitrogen.     

HCl介质中巯基三唑缓蚀吸附膜对碳钢的保护时间的研究

 合成两种新型巯基三唑缓蚀剂，利用交流阻抗测试(EIS)结果，建立了10 M HCl介质中缓蚀剂吸附膜对碳钢缓蚀保护作用时间的预测方程，分析了预膜时间和金属表面状态等因素对缓蚀吸附膜保护时间的影响.     

Synergistic effects of formaldehyde and alcoholic extract of plant leaves for protection of N80 steel in 15%HCl

Abstract

The synergistic effects of formaldehyde and an alcoholic extract of plant leaves have been studied by weight loss measurements at temperatures up to 363 K using various concentration ratios of the two inhibitors to protect N80 steel against corrosion in 15% hydrochloric acid. The inhibition efficiency was found to decrease with increasing temperature for all except two of the various concentration ratios that were studied. After identifying these two most promising mixtures, their corrosion prevention effects for N80 steel in hydrochloric acid were studied in more detail by weight loss and potentiostatic polarisation measurements. The corrosion rate of the steel was decreased by the presence of small additions of the inhibitors. The extent of decrease was found to depend on the nature of the corrosion inhibitor and its concentration. The inhibition efficiencies of the two plant based inhibitor mixtures were compared with those of two commercially available oil industry corrosion inhibitors. In all cases the adsorption of the inhibitors on the steel appeared to follow the Frumkin or Langmuir adsorption isotherm. The inhibition efficiencies of the two plant based inhibitors and the two commercial inhibitors were evaluated at a concentration level of 0.8% for temperatures in the range 303 K to 363 K) and exposure times of between 1 h and 24 h. Thermodynamic parameters including the free energy of adsorption, activation energy, enthalpy and entropy were calculated in both the absence and presence of inhibitors. Potentiostatic polarisation tests have revealed that inhibitors are primarily of the anodic type.     

从竹叶中提取酸洗缓蚀剂的研究

用浸泡提取法从竹叶中提取有机缓蚀组分,并将其作为盐酸酸洗缓蚀剂的主要成分.对以竹叶浸泡提取物为主的复合缓蚀剂的缓蚀效果进行了研究,采用线性极化法评价缓蚀剂的缓蚀效率,运用正交试验法优选缓蚀剂配方,并探讨其缓蚀机理.结果表明,最优配方对碳钢在5%的盐酸溶液中有优良的缓蚀效果,其缓蚀率达95.6%,属于混合型缓蚀剂.     

Inhibitorwirksamkeit beim Langzeitschutz von Stahlbehältern für die chemische Oberflächenvorbereitung gegen örtliche Korrosion durch salzsäurehaltige Prozesslösungen

Inhibitor efficiency in long‐time protection of steel tanks for the chemical surface preparation against local corrosion by process solutions containing hydrochloric acid The efficiency of prevailing acid inhibitors is examined by age hardening heavy tank‐steel plates in technically usual hot‐galvanizing solutions for 1000 hours. With acid inhibitors local corrosion emerged as shallow pit formation first and foremost in hydrochlorid acid pickles (20 g/l HCl) at ambient temperature as well as in cleaners containing hydrochloric acid (10–30 g/l HCl) at 40°C when other conditions also applied. Above all, local corrosion was produced if the inhibitor concentration became too low (0.2 g/l) in connection with a minimum hydrochloric acid concentration (10–30 g/l). However, oxidizing agents like iron(III)‐ions (5–10 g/l), atmospheric oxygen and free chlorine (100–1000 mg/l) lead to local corrosion, too. Local corrosion did not emerge in rinse baths (2–10 g/l HCl) and fluxing material solutions of zinc chloride and ammonium chloride (pH value: 2.0–5.5). Here uniform corrosion developed. Acid inhibitors turned out to be very effective against uniform corrosion in the examined long‐time period (inhibiting values up to 99%).     

Methylamine als Korrosionsinhibitoren für Aluminium 57-S in Salzsäure

Methylamines as corrosion inhibitors for Al-57 S in hydrochloric acid solutions Methylamine, dimethylamine and trimethylamine have been investigated as corrosion inhibitors for aluminium-57 S in hydrochloric acid solutions. Of the three substances studied, dimethylamine is the best inhibitor as indicated by loss in weight measurements and polarisation studies. Studies of cathodic protection to aluminium-57 S in 2.0 N hydrochloric acid but becomes positive in the presence of inhibitors.     

Korrelationsbetrachtungen zum Einfluß von Säureinhibitoren auf die Metallauflösungsgeschwindigkeit und die Kinetik der Wasserstoffabsorption

Considerations on the correlations between inhibition of metal dissolution and hydrogen absorption in the use of acid inhibitors Evaluating literature data on the impact of 53 quarternary ammonium salts, 13 aliphatic and aromatic aldehydes and 12 aliphatic and aromatic ketones on the inhibition of the rate of metal dissolution and the hydrogen permeation currents at steel in H₂S-free and H₂S-saturated 16% hydrochloric acid at ambient temperature, it is demonstrated by rank correlation considerations that there is no correlation between activity in blocking the metal dissolution rate and efficiency in decreasing the hydrogen absorption rate of the metal. Furthermore, there is no correlation between antipromotor/promotor-efficiency at the free corrosion potential and at cathodic polarization in H₂S-free and H₂S-saturated acid. Problems of H-absorption therefore have to be investigated for any particular case under conditions as close to the practice as possible.     

Über den Einfluß von Thioharnstoff und Thioharnstoff-Derivaten als Beizinhibitoren auf die Wasserstoffaufnahme,die Inhibitorwirksamkeit und die Wechselbiegefestigkeit von Kohlenstoffstahl bei der Säurebeizung

Influence of thiourea and its derivatives as pickling inhibitors on hydrogen pickup, degree of inhibition and fatigue load of carbon steel during pickling in acids The influence of additions of thiourea (TU), N-methyl-TU, N, N′-tetramethyl-TU, N-phenyl-TU, N, N′-diethyl-TU and N, N′-diphenyl-TU upon the acid pickling of mild steel (1,0 M H₂SO₄ at 50° C) was investigated. Measured were inhibitor efficiency, uptake of hydrogen and alternating bending strength of the samples as functions of inhibitor type and inhibitor concentration. With all inhibitors a maximum of inhibitor efficiency and alternating bending strength and a minimum of hydrogen uptake was found in the same inhibitor concentration range of about 0,001 M. Compared to pickling in pure sulfuric acid at this optimum concentration the inhibitor efficiency is between 95,2 and 98,4%, the decrease of the hydrogen uptake between 8,6 and 63,3% and the increase of the alternating bending strength between 20,0 and 43,4%, depending upon the kind of inhibitor. The alternating bending strength increases roughly linearly with decreasing hydrogen content of the samples. In the optimum concentration range the inhibitor efficiency and the alternating bending strength increase, the hydrogen uptake decreases roughly linearly with increasing adsorption area or increasíng molecular weight of the inhibitors.     

Untersuchung von Säureinhibitoren hinsichtlich ihrer Wirkung gegenüber H-induzierter Korrosion

Investigation of Inhibitors Regarding Weight Loss Corrosion and Hydrogen Absorption in Acids It is theoretically shown that a relationship between inhibition of weight loss and hydrogen induced corrosion cannot be generally expected. Ten commercial inhibitors for pickling and sour gas service have been investigated. A correlation between the two kinds of corrosion mentioned above does not exist. In all cases the inhibitors were found to decrease the hydrogen absorption rate. This effect depends on the medium without any correlation. From these results one cannot compare inhibition of weight loss corrosion with that of hydrogen absorption. Furthermore, an inhibition of hydrogen-induced corrosion phenomena (HIC, HSCC) can only be evaluated by permeation measurements under service conditions.     

Effect of corrosion medium composition on rate of crack growth in X70 pipeline steel

The growth rates of corrosion cracks in X70 pipeline steel are determined in weakly acidic (pH 5.5) buffer solution with additives of a number of compounds that are a part of the soil electrolyte or are steel corrosion inhibitors. It is shown that the effect of components of electrolyte on the rate of crack growth agrees fairly well with their stimulating or inhibiting effect on the anodic dissolution of iron. The rates of hydrogen permeation into steel are measured and the effect of hydrogen absorbed by the metal on the anodic process in the studied corrosion media is considered.     

Struktur-Wirkungs-Prinzipien von Korrosionsinhibitoren für die Rohöl- und Erdgasförderung

Structure efficiency relationships of corrosion inhibitors for oil and gas production Structure efficiency relationships for quarternary ammonium compounds as corrosion inhibitors for oil and gas production were investigated in the system mild steel/aqueous NaCl solution (5 weight%, CO₂ saturated) at T = 298 K and T = 343 K by Electrochemical Impedance Spectroscopy (EIS) and weight loss measurements. In-situ EIS measurements rapidly gave relatively accurate results on differential inhibitor efficiencies. Composition, thickness and inhibitor content of the inhomogeneous 3-D protecting layers formed on highly pure iron surfaces were determined by XPS measurements. The inhibition mechanism of the inhibitor used could be determined by its distribution within the 3-D protecting surface layer and is interpreted in terms of the interphase inhibition concept.     

Inhibiting effects of some mercapto-triazole derivatives on the corrosion of mild steel in 1.0 M HCl medium

The effect of some mercapto-triazole derivatives synthesized in the laboratory containing different hetero atoms and substituents in the organic structures on the corrosion and hydrogen permeation of mild steel in 1.0 M HCl was investigated by weight loss and various electrochemical techniques. Results obtained reveal that all the mercapto-triazole derivatives perform excellently as corrosion inhibitors for mild steel in 1.0 M HCl. Potentiodynamic polarization studies have shown that all these compounds suppress both the anodic and cathodic process and they behave as mixed-type inhibitors. Double layer capacitance and charge transfer resistance values were derived from Nyquist plots obtained from AC impedance studies. Changes in impedance parameters are indicative of the adsorption of these compounds on the metal surface. The inhibition efficiency mainly depends on the nature of the investigated compounds. The values of the inhibition efficiency calculated from these techniques are in reasonably good agreement. The extent of reduction of hydrogen permeation current through mild steel surface was studied by the hydrogen electropermeation technique. The adsorption of these compounds on mild steel surface is found to obey Langmuir adsorption isotherm. The free energy of adsorption for inhibiting process was determined on the basis of Langmuir adsorption isotherm.     

Inhibierung der korrosion von Aluminium 2 S und 3 S in Salzsäure

Inhibition of the corrosion of aluminium 2S and 3S in hydrochloric acid The authors describe the influence of furfural on the corrosion of aluminium 2S and 3S in hydrochloric acid of different concentrations. Even in low concentrations, furfural is found to be an extremely effective inhibitor. Its inhibitive effects increase with its concentration up to a maximum, and then decrease again. The cause of this decrease is cathodic depolarisation with high furfural concentrations. The inhibiting effect of furfural is based on the increase in cathodic polarisation. In general, aluminium 2S obtains a better corrosion protection than aluminium 3S, with the exception of 0.5 n HCl in which aluminium 2S is not protected. The effectiveness of the inhibitor is better with higher hydrochloric acid concentrations.     

HCl介质中双季铵盐对碳钢的缓蚀作用

合成了一种双季铵盐缓蚀剂(BQA)，分别用腐蚀失重 法和电化学测试法研究了其在HCl介质中对碳钢的缓蚀作用及缓蚀机理.结果显示，对碳钢 在1.0 mol/L HCl溶液中BQA是一种性能优异的缓蚀剂.     

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.