Investigations of an ethanolamine‐based corrosion inhibitor system for surface treatment of reinforced concrete

Laboratory investigations were performed to assess the efficacy of a proprietary ethanolamine‐based corrosion inhibitor system when applied to the surface of reinforced concrete specimens that were chloride‐contaminated to varying extents in the presence or absence of carbonation. The corrosion responses of embedded steel bars at various depths of cover were monitored electrochemically during a controlled programme of cyclic wetting and drying undertaken for several months prior to the inhibitor treatment and for approximately eighteen months thereafter. Gravimetric measurements of the quantities and distribution of corrosion on the steel were also made on completion of the exposure tests. Analysis of aqueous extracts from treated concrete revealed that the ethanolamine component of the inhibitor system penetrated to depths of more than 15 mm within the concrete. It was found that, for inhibitor‐treated specimens, there was some reduction in the corrosion rate of pre‐corroding steel at low cover depths in non‐carbonated concrete with modest levels of chloride contamination. At higher levels of chloride contamination and in carbonated specimens, however, the ethanolamine‐based inhibitor was apparently ineffective under the conditions investigated.     

Corrosion inhibitor systems for remedial treatment of reinforced concrete. Part 2: sodium monofluorophosphate

Sodium monofluorophosphate (MFP) has been applied in the form of concentrated aqueous solutions to the surfaces of concrete structures with the aim of inhibiting corrosion of embedded reinforcing steel which has become depassivated as a consequence of carbonation and/or chloride contamination. To evaluate the effectiveness of such treatments, a series of laboratory investigations was undertaken with reinforced concrete specimens that were chloride-contaminated to varying extents in the presence or absence of carbonation. The corrosion responses of embedded steel bars at various depths of cover were monitored electrochemically during a controlled programme of cyclic wetting and drying undertaken for several months prior to the inhibitor treatment and for approximately 18 months thereafter. Gravimetric measurements of the quantities and distribution of corrosion on the steel were also made on completion of the exposure tests. It has been found that there were no marked reductions in the corrosion rates of the steel under the conditions investigated. Analysis of aqueous extracts from the treated concrete specimens by means of ion chromatography revealed that negligible penetration of soluble MFP ions had occurred into any of the specimens. Hydrolysis products of MFP (phosphate and fluoride) were present at significant depths in aqueous extracts of the carbonated concrete specimens but only fluoride was detectable in similarly obtained aqueous extracts of non-carbonated specimens.     

Self-healing polymer coatings with cellulose nanofibers served as pathways for the release of a corrosion inhibitor

Polymer coatings containing cellulose nanofibers were applied to carbon steel for corrosion inhibition. The specimens were scratched with a knife-edge, and then polarization resistance was monitored in a sodium chloride solution. The polarization resistance of the scratched specimen containing nanofibers and corrosion inhibitor was higher than that of a polymer coating that contained only a corrosion inhibitor. The optimal mixing ratio of corrosion inhibitor for cellulose nanofibers was 4. Empty holes were confirmed on a cross-section of the polymer coating after the corrosion test, which showed that the nanofibers served as pathways for the release of the corrosion inhibitor.     

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.     

Inhibition of atmospheric corrosion of mild steel by sodium benzoate treatment

The objective of this study was to evaluate the effectiveness of sodium benzoate as an inhibitor to slow down or prevent atmospheric corrosion/discoloration of the local mild steel during storage in the Arabian Gulf region. Test specimens were prepared from locally produced reinforcing steel products. The inhibitor solution was applied on steel specimens at a concentration of 100 mM for 1 day at room temperature. Wooden exposure racks were used to hold as-received and inhibitor-treated specimens during atmospheric exposure for different periods. Corrosion was evaluated through weight loss determination and electrochemical technique. As expected, the Arabian Gulf atmosphere was corrosive on the as-received local mild steel. On the other hand, treatment of steel with sodium benzoate lowered its corrosion rate during initial days of its exposure to atmosphere. However, atmospheric corrosion inhibition performance of sodium benzoate deteriorated with exposure time after 30 or more days of atmospheric exposure, and the corrosion rates of sodium benzoate-treated specimens reached that of the unprotected specimens at the end of 90 days of atmospheric exposure.     

The corrosion of steel and aluminium in calcium chloride/ammonia,magnesium chloride/methylamine and magnesium chloride/methylamine/decane

The corrosion of St 37, StE 36, Al 99,5 and Al-Mg 3 in the chemical pairs of substances calcium chloride/ammonia, magnesium chloride/methylamine and magnesium chloride/methylamine/decane was investigated. The corrosion tests were performed in autoclaves at room temperature to 180 °C. The nominal duration of the experiments was 1000 hours. Rod shaped fatigue specimens with polished surfaces served as test specimens; these were fatigue tested after the corrosion treatments. All materials tested were compatible with calcium chloride/ammonia under the experimental conditions employed. Steel and aluminium showed similar behaviour against magnesium chloride/methylamine and magnesiumchloride/methylamine/decane, respectively. At room temperature and 70°C to 80°C the corrosion of steel and aluminium was low (wall losses in the order of 1 m?m/a). Corrosion increased with increasing temperature. The activation energy for the reaction, which determined the rate of weight loss in magnesium chloride/methylamine/decane, was AE_st = 0, 60 ± 0,18 eV for steel, and AE_Al = 1, 07 ± 0,07 eV for aluminium. A corrosion treatment on aluminum fatigue specimens after 1000-1500 hours at 110 °C caused a notable decrease in fatigue strength; no such behaviour was noted for steel, even when corroded at 170 °C.     

Mitigation of Stress Corrosion Cracking Susceptibility of Machined 304L Stainless Steel Through Laser Peening

The paper describes an experimental study aimed at suppressing stress corrosion cracking susceptibility of machined 304L stainless steel specimens through laser shock peening. The study also evaluates a new approach of oblique laser shock peening to suppress stress corrosion cracking susceptibility of internal surface of type 304L stainless steel tube. The results of the study, performed with an indigenously developed 2.5 J/7 ns Nd:YAG laser, demonstrated that laser shock peening effectively suppresses chloride stress corrosion cracking susceptibility of machined surface of type 304L stainless steel. In the investigated range of incident laser power density (3.2-6.4 GW/cm²), machined specimens peened with power density of 4.5 and 6.4 GW/cm² displayed lower stress corrosion cracking susceptibility considerably than those treated with 3.2 and 3.6 GW/cm² in boiling magnesium chloride test. Oblique laser shock peening, performed on machined internal surface of a type 304L stainless steel tube (OD = 111 mm; ID = 101 mm), was successful in introducing residual compressive surface stresses which brought about significant suppression of its stress corrosion cracking susceptibility. The technique of oblique laser shock peening, in spite of its inherent limitations on the length of peened region being limited by tube internal diameter and the need for access from both the sides, presents a simplified approach for peening internal surface of small tubular components.     

Korrosionsverhalten von ungeschütztem und feuerverzinktem Stahl bei der Lagerung von Heizöl

Corrosion behaviour of unprotected and hot-dipped galvanized steel for fuel oil storage Investigations have been done with unprotected and galvanized steel under fuel oil storage conditions. By adding sodium chloride as corrosive agent and a commercial corrosion inhibitor conditions for localized corrosion of unprotected steel were simulated. Results show that no localized corrosion occurs with galvanized steel.     

Self-healing capability of porous polymer film with corrosion inhibitor inserted for corrosion protection

Porous polymer films with varying pore sizes were prepared by changing the evaporation time of an organic solvent. A specimen was prepared consisting of porous polymer film containing corrosion inhibitor coated onto carbon steel. The specimens were scratched with a knife-edge, and the polarization resistance was monitored in a sodium chloride solution. An increase in polarization resistance was confirmed, and the films with larger-sized pores demonstrated a higher self-healing capability.     

Corrosion testing on steel reinforced XD3 concrete samples prepared with a green inhibitor and two different superplasticizers

In recent years, the use of corrosion inhibitors in producing high‐performance steel reinforced concrete structures has increased significantly to minimize the chloride and sulfate attacks. However, most inhibitors available in the market are toxic to the environment. Hence, one objective of the present investigation was to test a novel, eco‐friendly, so‐called green inhibitor extracted from a fruit waste (orange peel), and its effects were studied on the compression strength of the XD3 type concrete samples. The inhibitor was added to the concrete mix in concentrations of 1% and 3% by weight of cement in addition to two different superplasticizers (Mapei Dynamon SR 31, Budapest, Hungary and Oxydtron, Hungary). The test results on steel reinforced samples immersed in 3.5 wt% NaCl aqueous solutions at room temperature showed promising corrosion mitigating effects just after 6 months testing period. The lower corrosion currents (i.e., better corrosion resistance) after 6 months immersion were observed when the samples contained both green inhibitor and Oxydtron superplasticizer, especially with sample C2 (in this case 3% green inhibitor was added to the mixture of cement + Oxydtron superplasticizer).     

Verfahren zur Prüfung eines Inhibitors gegen Chlorid-Korrosion an unlegiertem Stahl

Method for testing inhibitors of chloride corrosion on unalloyed steel An accelerated test for screening pitting inhibitors for steel fuel oil tanks. Time-potential curves for assessing the stable rest potential yield no reliable information as to the efficiency of inhibitor additions of various concentrations. Depending on inhibitor concentration a steep increase of current associated with pitting is observed at certain distances from the rest potential. The potentiostatic measurement of the break-down potential of chloride ions yields very accurate results but is very time consuming; this is why cinetic polarisation tests (2 mV/min) have been made. According to the results obtained the steel is protected against pitting only when polarisation can be continued to the point of oxygen evolution without a break-through of chloride ions. The test duration is only one day as compared to 3–5 months with normal immersion tests.     

缓蚀剂9912-1在CO_2H_2O介质中缓蚀性能的研究

设计合成了一种成膜型的氮杂环的季胺盐缓蚀剂 9912 1。测试了其在 90℃下二氧化碳饱和的 3%NaCl水溶液中对碳钢的缓蚀性能 ,探讨了缓蚀剂用量与缓蚀率的关系 ,及其与复配物的协同效应 ,从中得出了较佳的缓蚀配方。实验结果表明 ,此种缓蚀剂对碳钢有良好的缓蚀效果 ,可作为中高温条件下CO2 环境中的缓蚀剂。     

Effect of height on the corrosion of steel and galvanized steel in nontropical coastal marine environments

In this study, the behavior of carbon steel and galvanized steel in nontropical coastal marine environments was evaluated. Evaluation was carried out with specimens with dimensions of 10 cm × 10 cm × 0.3 cm. These specimens were exposed to four testing stations (Iquique, Mejillones, Los Vilos, and San Vicente), where racks were installed both at ground level (ground), as well as in the upper zone of electrical transmission towers (tower). In each station, 24 specimens of A36 carbon steel and galvanized steel were placed (12 each). The corrosivity of the environment was measured using the ISO 9223, 9225, and 9226 standards. The specimens were evaluated on-site, monthly, through visual inspection and photographic record. Once withdrawn, the corrosion rate was determined and the corrosion products were analyzed through Raman and Fourier-transform infrared. The results show that, in all cases, the corrosion rate is greater in the tower than on the ground. However, even though the Los Vilos station is located farther from the sea (3,500 vs. ≈500 m), the corrosion rate of steel in the tower is the highest. This is caused by the generation of HCl from the transformation of lepidocrocite into goethite, in the presence of low chloride content, which acidifies the steel/corrosion product interface. In the case of galvanized steel, the corrosion rate is a function of the chloride content in the atmosphere, obtaining an excellent correlation between both parameters.     

Corrosion of maraging steels in chloride solutions

Abstract

The effect of a maraging heat treatment on the mechanical properties and corrosion behaviour of a special grade of heat treatable stainless steel has been studied. Although the mechanical properties such as strength and hardness of this steel are enhanced after the maraging heat treatment, its corrosion resistance is reduced as a result of the formation of intermetallic precipitates at the grain boundaries. In addition, oxide scales are formed on the surface of the specimens after the heat treatment owing to high temperature oxidation and these scales play an important role in the corrosion behaviour of the aged specimens. Corrosion studies have been conducted on underaged, peak aged, and overaged specimens with and without oxide scales and on specimens in the solution annealed condition. Impedance and potentiostatic anodic polarisation techniques in 3·5%NaCl of pH 1, 4, 7, and 10 at room temperature have been used. The corrosion performance order of this maraging steel with oxide scales in acidic, neutral and alkaline solutions is solution annealed> overaged> underaged> peak aged. The removal of oxide scales from the surface of the aged specimens by electropolishing considerably enhances the corrosion resistance without altering the performance order. The surface treated specimens behave in a similar manner to the solution annealed specimens in chloride solutions of pH 7 and 10. This tremendous increase in the corrosion resistance value is a result of the formation of a passive. film on the surface of the specimens during the surface treatment. In immersion tests the surface treated specimens show no signs of corrosion after immersion in 3·5%NaCl at room temperature for a prolonged period of time.     

Effect of inhibitor treatment on corrosion of steel in a salt solution

This study examined experimentally different chemicals for inhibition of steel corrosion in a simulated aqueous solution for the industrial marine atmosphere of the Arabian Gulf region. The literature reported various inhibitors that can help in protection against metal corrosion in aqueous environments. Among them, 10 inhibitors (calcium silicate, cyclohexylamine, n-methylcyclohexylamine, dicyclohexylamine nitrite, sodium benzoate, sodium nitrate, sodium nitrite, sodium phosphate, sodium dihydrogen orthophosphate, and magnesium nitrate hexahydrate) were obtained and corrosion resistance of inhibitor applied steel specimens were examined in the simulated solution (2 wt.% NaCl and 1 wt.% Na₂SO₄). Test specimens were prepared from locally produced reinforcing steel products. Treatment of steel with either dicyclohexylamine nitrite or sodium dihydrogen orthophosphate both at 10 mM concentration for 1 day at room temperature resulted in significant inhibition of corrosion. No significant improvement in corrosion inhibition was observed either with an increase in inhibitor concentration at room temperature or with an increase in inhibitor application temperature at 10 mM concentration. A further study is planned to examine the inhibition performances of the two inhibitors under actual atmospheric conditions in the Arabian Gulf region (industrial marine environment).     

Inhibition of steel corrosion by calcium benzoate adsorption in nitrate solutions

The inhibitive properties of calcium benzoate for steel corrosion were studied in sodium nitrate solutions at room temperature. Corrosion parameters of the steel/nitrate and steel/benzoate + nitrate interfaces were obtained from polarisation curves. Adsorption parameters of benzoate on steel in sodium nitrate solutions were determined through changes in the degree of surface coverage by the inhibitor, as a function of concentration, time and adsorption potential. The effect of chloride on the corrosion inhibition of benzoate was analysed exposing the metal in different chloride solution concentrations.     

Chloride threshold for rebar corrosion in concrete with addition of silica fume

The effect of silica fume on the chloride threshold for the initiation of pitting corrosion of steel in concrete was investigated. Laboratory tests were carried out in concrete specimens made with ordinary Portland cement and with 10% of silica fume. Chloride contents up to 2% by mass of cement were added to the mixes, in order to investigate the corrosion rate of embedded bars made of both strengthened and mild steel. A lower chloride threshold was observed in the bars which were embedded in concrete with silica fume compared to those embedded in concrete made of Portland cement.     

矿物掺合料对钢筋氯盐腐蚀行为的影响及其作用机理

用水泥提取液模拟混凝土孔隙液,用自腐蚀电位、动电位极化和电化学阻抗技术,研究单掺粉煤灰或矿粉、复掺粉煤灰和矿粉对混凝土中钢筋氯盐腐蚀行为的影响.结果表明,粉煤灰和矿粉均能有效降低钢筋受氯离子腐蚀的风险,减小腐蚀速率,并能不同程度地提高钢筋腐蚀的临界氯离子浓度.抑制氯离子腐蚀能力由强到弱依次为:矿粉>矿粉+粉煤灰>粉煤灰>水泥.且随氯离子浓度的增大,矿粉和粉煤灰的阻锈效率会有不同程度的下降.用矿粉和粉煤灰按适当比例复掺的方法来对抗氯离子腐蚀不仅经济,而且有不错的阻锈效果.     

Chloride threshold level for corrosion of steel in concrete

The steel rebar inside reinforce concrete structures is susceptible to corrosion when permeation of chloride from deicing salts or seawater results in the chloride content at the surface of the steel exceeding a chloride threshold level (CTL). The CTL is an important influence on the service life of concrete structures exposed to chloride environments. The present study discusses the state of art on the CTL for steel corrosion in concrete, concerning its measurement, representation, influencing factors and methods to enhance the CTL. As the CTL values reported in the majority of previous studies were varied with experimental conditions, corrosion initiation assessment method, the way in which the CTL was represented, direct comparison between the results from different sets and evaluation was subjected to the difficulty. As a result, total chloride by weight of cement or the ratio of [Cl⁻]:[H⁺] is the best presentation of CTL in that these include the aggressiveness of chlorides (i.e. free and bound chlorides) and inhibitive nature of cement matrix. The key factor on CTL was found to be a physical condition of the steel-concrete interface, in terms of entrapped air void content, which is more dominant in CTL rather than chloride binding, buffering capacity of cement matrix or binders. The measures to raise the CTL values using corrosion inhibitor, coating of steel, and electrochemical treatment are also studied.     

P110钢盐酸酸化缓蚀剂QL-1的合成及应用性能

选用非离子表面活性剂平平加-O溶液作为合成反应的溶剂,喹啉和卤代烃经季铵化反应合成一种喹啉季铵盐酸化缓蚀剂QL-1。借助红外光谱仪对合成产物结构进行了表征,并采用静态失重法和电化学极化曲线和电化学阻抗法对药剂QL-1进行了缓蚀性能评价及电化学机理分析。红外光谱分析证明了该产物分子结构符合预先设定结构。静态失重法结果表明,随着该缓蚀剂浓度的增加,P110钢试片在15%和20%盐酸溶液中的腐蚀速率随之减小;随腐蚀时间的延长和腐蚀温度的升高,P110钢试片在盐酸溶液中的腐蚀速率均逐渐增大。电化学交流阻抗谱和极化曲线结果表明,该缓蚀剂在P110钢表面形成了明显的保护性膜,并且是一种以抑制阴极反应过程为主、作用机理属于"负催化效应"的混合型缓蚀剂。