Adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl) (phenyl)methyl)urea on the carbon steel corrosion in hydrochloric acid media

The adsorption effect of 1‐((2‐hydroxynaphtalen‐1‐yl)(phenyl)methyl)urea (HNPU) on corrosion behavior of carbon steel in 1 M hydrochloric acid solution was investigated using weight loss, potentiostatic polarization, and infrared spectroscopy methods. Surface morphology was studied by scanning electron microscopy (SEM). The experimental results, suggest that HNPU inhibited the corrosion of carbon steel in acid solution and the inhibition efficiencies increased as the concentration of the compound in the solution was increased. The calculated inhibition efficiencies from the two investigated methods were in good agreement. Potentiostatic polarization measurements indicate that HNPU acts as a mixed‐type inhibitor. The adsorption of the inhibitor on the carbon steel surface obeys Langmuir adsorption isotherm. The values of activation energy and the thermodynamic parameters, such as adsorption equilibrium constant (K_ads), adsorption free energy (ΔG_ads), adsorption heat (ΔH_ads), and adsorption entropy (ΔS_ads) values were calculated and discussed. The results obtained from infrared spectra, confirmed the adsorption of inhibitor on the alloy surface after immersion in acidic solution containing HNPU. The SEM analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acidic solution containing HNPU than that in blank.     

Two‐step electrosynthesis of polypyrrole for corrosion protection of stainless steel

Smooth polypyrrole (PPy) films were successfully electrosynthesized on a stainless steel (SS, 1Cr18Ni9) surface by a self‐catalytic two‐step process. SS substrate dissolution during PPy electrosynthesis was effectively depressed. The redox properties and corrosion behavior of PPy film coated SS electrodes were investigated by cyclic voltammetry, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization. The reduction of PPy was found to include two reaction processes: an anion dedoping process and a cation insertion process. The PPy film was found to lose its electroactivity when polarized at high potentials due to peroxidation. EIS of SS/PPy mainly corresponds to PPy film response and charge transfer resistance decreases as film thickness increases, indicating that SS corrosion can be inhibited effectively by the PPy film.     

The corrosion inhibitory property of N,N‐bis(2‐benzimidazolylmethyl)amine for Q235 steel

The main purpose of this paper is to systematically evaluate the anti‐corrosion property of N,N‐bis(2‐benzimidazolylmethyl)amine (IDB), which is a novel good thermal stabilized inhibitor in acidic medium. Results obtained from electrochemical tests and corrosion surface morphology analyses reveal that IDB performs excellently as corrosion inhibitor for Q235 steel in 1 mol/L hydrochloric acid corrosive solution. Potentiodynamic polarization measurements show that IDB inhibits both the anodic and cathodic processes of corrosion and exhibits as a mixed‐type inhibitor. Besides, the inhibiting efficiency (IE%) and consequently the degree of surface coverage (θ) increase with the inhibitor concentration rising. And when the concentration is 20 × 10^?5 mol/L, the corrosion inhibition effect is best to reach 96.39%. The adsorption of inhibitor on Q235 steel is found to obey the Langmuir adsorption isotherm, and the calculated Gibbs free energy demonstrates that IDB spontaneously adsorbs and forms a protective chemisorbed film on Q235 steel to restrain its corrosion. Hereby, IDB will become a promising corrosion inhibitor in further.     

时效制度对2205双相不锈钢耐蚀性能的影响

以2205双相不锈钢板为研究对象,研究了时效温度、时效保温时间和冷却速度对不锈钢板动电位极化曲线的影响,观察了固溶和不同时效热处理制度下试样的微观组织形貌,分析了影响双相不锈钢板耐腐蚀性能的主要因素。结果表明,950 ℃时效时具有最好的耐腐蚀性能,而在时效温度为850 ℃时耐腐蚀性能最差;当时效后冷却方式由空冷变成水冷后,不锈钢的耐均匀腐蚀性能和抗点蚀性能都得到了改善。     

Rhodanine azosulpha drugs as corrosion inhibitors for corrosion of 304 stainless steel in hydrochloric acid solution

The effect of rhodanine azosulpha drugs on the corrosion behaviour of 304 stainless steel in 1.0 M hydrochloric acid solution as corrosive medium has been investigated using weight loss and potentiostatic polarization techniques. Some corrosion parameters such as anodic and cathodic Tafel slope, corrosion potential, corrosion current, exchange current densities, surface coverage and inhibition efficiency were calculated. The polarization measurements indicated that the inhibitors are of mixed type and inhibit corrosion by parallel adsorption on the surface of steel due to the presence of more than one active centre in the inhibitor molecule. The adsorption is obeyed Langmuir adsorption isotherm. The activation energy and thermodynamic parameters were calculated at different temperature.     

Influence of sigma-phase formation on the localized corrosion behavior of a duplex stainless steel

Because of their austenitic-ferritic microstructures, duplex stainless steels offer a good combination of mechanical and corrosion resistance properties. However, heat treatments can lower the mechanical strength of these stainless steels as well as render them susceptible to intergranular corrosion (IGC) and pitting corrosion. In this study, a low-carbon (0.02%) duplex stainless steel is subjected to various heat treatments at 450 to 950 °C for 30 min to 10 h. The heat-treated samples then undergo ASTM IGC and pitting corrosion tests, and the results are correlated with the microstructures obtained after each heat treatment. In the absence of Cr₂₃C₆ precipitation, σ-phase precipitates render this duplex stainless steel susceptible to IGC and pitting corrosion. Even submicroscopic σ-phase precipitates are deleterious for IGC resistance. Longer-duration heat treatments (at 750 to 850 °C) induce chromium diffusion to replenish the chromium-depleted regions around the σ-phase precipitates and improve IGC resistance; pitting resistance, however, is not fully restored. Various mechanisms of σ-phase formation are discussed to show that regions adjacent to σ-phase are depleted of chromium and molybdenum. The effect of chemical composition (pitting resistance equivalent) on the pitting resistance of various stainless steels is also noted.     

Mechanism of improved corrosion resistance of type 304l stainless steel,nitric acid grade,in nitric acid environments

Materials for critical components in nuclear fuel reprocessing plants are required to have low corrosion rates and long designed life because access for repairs is not possible. Stainless steel type 304L, nitric acid grade (NAG), is the new material suitable for such applications. It has guaranteed low corrosion rates and is not susceptible to intergranular corrosion (IGC) in nitric acid environments. The corrosion behavior of type 304L stainless steel, NAG, and type 304L stainless steel, commercial purity (CP), in nitric acid environments is investigated in detail. Studied are: microstructural mapping in the three directions (longitudinal, long transverse, and short transverse), effect of sensitization heat treatment, resolution annealing and sensitization heat treatment for the as-received and cold-worked samples of the two varieties on the resultant microstructures. The anodic polarization characteristics along the three directions for both varieties in 1N HNO₃ are compared. The susceptibility of both varieties to end grain corrosion in 9N HNO₃ + 1 g Cr⁺⁶/liter boiling solution is assessed, and microstructural examination of the exposed sample is carried out to compare the degree of end grain corrosion. Their susceptibility to IGC due to segregation of impurity elements to grain boundaries is also compared. It is shown that controlled microstructure (fine grain size, retained cold work, and discrete precipitation at grain boundaries) along with controlled chemical composition is responsible for improved corrosion resistance of the NAG variety. The NAG variety has much less susceptibility to corrosion along the long- and short-transverse directions and, therefore, less susceptibility to end grain corrosion. The means and consequences of controlling chemical composition are also discussed.     

Polyaspartic acid as a green corrosion inhibitor for carbon steel

The inhibitor effect of the environmentally friendly corrosion inhibitor polyaspartic acid (PASP) on the corrosion of carbon steel in 0.5 M H₂SO₄ was investigated by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Polarization curve results clearly reveal the fact that PASP is a good anode‐type inhibitor. EIS results confirm its corrosion inhibition ability. The inhibition efficiency increases with increasing PASP concentration, and the maximum inhibition efficiency was 80.33% at 10 °C. SEM reveals that a protective film forms on the surface of the inhibited sample. The adsorption of this inhibitor is found to follow the Freundlich adsorption isotherm. A mechanism is proposed to explain the inhibitory action of the corrosion inhibitor.     

双相不锈钢堆焊层应力腐蚀性能评价

为防止换热器等设备发生应力腐蚀,工程上试采用在与腐蚀介质接触的表面堆焊2205双相不锈钢.为探索方案的应用范畴与可行性,对两种焊接工艺(自动焊及焊条电弧焊)、3种工程上常见腐蚀环境(饱和硫化氢、氯化镁、氯化钙),通过恒负荷拉伸试验方法及断口微观分析手段,综合评价其应力腐蚀性能,并根据试验结果建立应力-寿命数学模型.结果表明,饱和H2S环境中恒负荷拉伸门槛值σth自动焊为0.45ReL、焊条电弧焊为0.4ReL,二者相差17％.氯化钙环境中0.9ReL应力下96 h试验后所有试样完好,显示出优良的抗氯化钙应力腐蚀能力.而该材料则不适于在沸腾氯化镁环境下工作.     

1,3‐Bis‐dibutylaminopropan‐2‐ol as inhibitor for reinforcement steel in chloride‐contaminated simulated concrete pore solution

An organic compound, 1,3‐bis‐dibutylaminopropan‐2‐ol (BDAP) was prepared and tested experimentally as inhibitor for reinforcement steel in simulated concrete pore solution. The electrochemical behavior of carbon steel electrodes immersed in simulated pore solutions with different concentration of BDAP was investigated by electrochemical measurements. Adsorption isotherm was determined based on the inhibition efficiency. The surface composition was evaluated via X‐ray photoelectron spectroscopy (XPS) as well in order to verify the presence and adsorption property of BDAP. The results showed that BDAP could effectively suppress the anodic process of carbon steel corrosion and the inhibition efficiency was improving with the increase of inhibitor concentration. BDAP could adsorb on carbon steel surface according to Langmuir adsorption isotherm. XPS spectrum certified the existence of BDAP on the steel surface.     

Damage of stainless steel bars due to atmospheric corrosion

In addition to constructional requirements in civil engineering stainless steels often have to fulfil high visual demands. Unexpected impairments of the visual appearance of stainless steels under low corrosive conditions are a widespread problem today. Frequently it is supposed that this is caused by changes in the alloy composition, worse environmental conditions or improper handling. Within a research project the systematic investigation of several cases of damaged stainless steel bars has shown that the reasons are based on well‐known material defects like chemical inhomogeneities (e.g. precipitations or local carburization) or geometrical defects (e.g. undercuts, rolling defects or shell formation). Thus, the failures could be clearly identified as production failures of the respective semi‐finished products.     

Stress corrosion cracking for 316 stainless steel clips in a condensate stabilizer

In one of the gas processing facilities in Abu Dhabi, UAE; a case of 316L stainless steel material failure occurred in the fractionating column due to stress cracking corrosion twice in a cycle of less than 2 years. This paper studies the stress corrosion cracking behavior of the 316L stainless steel in an accelerated corrosion environment and compares it with a higher corrosion resistant nickel alloy (Inconel 625). The experimental work was designed according to ASTM G36 standard, the samples were immersed in a boiling magnesium chloride medium which provided the accelerated corrosion environment and the tested samples were shaped into U‐bend specimens as they underwent both plastic and elastic stresses. The specimens were then tested to determine the time required for cracks to initiate. The results of the experimental work showed that the main mode of failure was stress corrosion cracking initiated by the proven presence of chlorides, hydrogen sulfide, and water at elevated temperatures. Inconel 625 samples placed in the controlled environment showed better corrosion resistance as it took them an average of 56 days to initiate cracks, whereas it took an average of 24 days to initiate cracks in the stainless steel 316L samples. The scanning electron microscopy (SEM) micrographs showed that the cracks in the stainless steel 316L samples were longer, wider, and deeper compared to the cracks of Inconel 625.     

不锈钢A-TIG焊接头的抗腐蚀性能分析

用沸腾硝酸腐蚀法和室温硫酸加硫酸铜溶液浸蚀法对奥氏体不锈钢TIG焊和自制活性剂A-TIG焊接头进行了对比腐蚀试验.结果表明,自制活性剂A-TIG焊接头在室温下具有良好的耐硫酸腐蚀能力,比TIG焊接头有更强的抗沸腾硝酸腐蚀能力.焊缝金属的化学成分分析表明,自制活性剂在焊接过程中能抑制金属中Cr、Ni等合金元素的烧损,因此提高了A-TIG焊接头的抗腐蚀性能.     

Poly(3‐octylthiophene) thermally treated as coating for corrosion protection of SS304 in sulfuric acid media

Poly(3‐octylthiophene) (P3OT) was synthesized by direct oxidation of the 3‐octylthiophene monomer using ferric chloride (FeCl₃) as an oxidant. Using the drop‐casting technique, P3OT coatings were deposited onto 304 type stainless steel electrodes. For the purpose of determining the effect of thermal annealing on the corrosion protection of stainless steel with P3OT coatings, the coated electrodes were thermally annealed for 30 h at two different temperatures, 55 and 100 °C. The corrosion behavior of P3OT coated stainless steel was investigated in 0.5 M sulfuric acid (H₂SO₄) at room temperature using potentiodynamic polarization curves (PPC), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS). The results indicated that the thermally treated P3OT coatings improved the corrosion resistance of the stainless steel in 0.5 M H₂SO₄. The best corrosion protection was obtained by the P3OT coating annealed at 100 °C. In order to study the temperature effect on the morphology of the coatings before and after the corrosive environment and compare it with corrosion protection, atomic force microscopy (AFM) and scanning electronic microscopy (SEM) were used.