Free and Wilson correlation between the molecular structure of some imidazolines and their corrosion inhibiting properties

In deaerated media containing hydrogen sulfide, the inhibition of the corrosion of N 80 steel by a homologous series of imidazolines was measured potentiokinetically. The data obtained were correlated to the structure of these molecules by means of Free and Wilson relationships. These correlations, allowed the behaviour of some derivatives to be predicted successfully.     

WC对定向结构Ni60涂层耐蚀性能的影响研究

为了研究WC含量对Ni60合金涂层耐腐蚀性能的影响规律及相关机制,向Ni60合金粉体中添加不同质量分数的WC,通过高频感应重熔和强制冷却技术,在45^#钢表面制备WC添加的Ni60/WC复合定向结构涂层,采用SEM、EDS、XRD、电化学性能测试和浸泡实验等检测手段分析研究了WC颗粒增强Ni60合金的定向结构复合涂层的耐腐蚀性能及其机制。结果表明：随着WC添加量的增加,极化电阻先增大后减小,WC添加量10%时达到最大值9710.8 Ω;腐蚀电流密度先减小后增大,WC添加量10%时最小为1.34×10_^-6 A/cm_²。WC添加量对涂层显微形貌、元素分布、物相均有影响,进而影响涂层耐蚀性能。     

Computational simulations of the molecular structure and corrosion properties of amidoethyl, aminoethyl and hydroxyethyl imidazolines inhibitors

To proof the corrosion efficiency of hydroxyethyl, aminoethyl and amidoethyl imidazolines, they were evaluated by linear polarization resistance and polarization curves in deaerated 3% NaCl + Diesel + inhibitors saturated with CO₂ at 50 °C. The most efficient inhibitor was the amido ethyl imidazoline, with an efficiency of 97.88% whereas the least efficient was the hydroxyethyl imidazoline, with an efficiency of 88.8%. A theoretical study of the corrosion inhibition efficiency of these imidazoline derivatives, was carried out using density functional theory (DFT). The computational calculations were used to obtain information about their molecular structure and those properties related with the inhibition efficiency of these inhibitors. The obtained correlations and theoretical conclusions agree well with the experimental results.     

Inhibitive action of some plant extracts on the corrosion of steel in acidic media

The effect of extracts of Chamomile (Chamaemelum mixtum L.), Halfabar (Cymbopogon proximus), Black cumin (Nigella sativa L.), and Kidney bean (Phaseolus vulgaris L.) plants on the corrosion of steel in aqueous 1 M sulphuric acid were investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. EIS measurements showed that the dissolution process of steel occurs under activation control. Potentiodynamic polarization curves indicated that the plant extracts behave as mixed-type inhibitors. The corrosion rates of steel and the inhibition efficiencies of the extracts were calculated. The results obtained show that the extract solution of the plant could serve as an effective inhibitor for the corrosion of steel in sulphuric acid media. Inhibition was found to increase with increasing concentration of the plant extract up to a critical concentration. The inhibitive actions of plant extracts are discussed on the basis of adsorption of stable complex at the steel surface. Theoretical fitting of different isotherms, Langmuir, Flory-Huggins, and the kinetic-thermodynamic model, were tested to clarify the nature of adsorption.     

金属点阵材料结构参数的CT检测

针对金属点阵材料的结构参数开展了检测方法研究.高能束激光选区熔化点阵结构的连接杆经工业CT(电子计算机断层扫描)检测后得到的影像呈椭圆状,针对这一影像特征,依据椭圆上任意两点之间的最大几何距离为长轴这一概念,实现了单个椭圆位置参数、形状参数的自动识别,以及金属点阵结构几何参数的自动化检测.检测结果基本符合设计值,为其他...     

Quantum chemical studies of some amino acids on the corrosion of cobalt in sulfuric acid solution

The inhibitive effect of some amino acids, glycine (Gly), alanine (Ala), valine (Val), leucine (Leu), isoleucine (Ile), serine (Ser), threonine (Thr), methionine (Met), phenylalanine (Phe), tyrosine (Tyr), trytophan (Try), aspartic acid (Asp), asparagine (Asn), glutamic acid (Glu), and lysine (Lys) against the corrosion of cobalt surface is studied by means of semiempirical and density functional methods. The calculated quantum chemical parameters correlated to the inhibition efficiency are, the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the energy gap (ΔE), and Mulliken charges. It is found that the calculated results satisfactorily support the experimental findings.     

The action of micro bio species and some inhibitors on the corrosion of stainless steel

The influence of local factors on the susceptibility to crevice corrosion of stainless steel in seawater has been investigated with specimens of UNS S31600, 316 L in Adriatic Sea, at the location in Dubrovnik, Croatia. Besides the other factors, as salinity, redox potential, oxygen content, temperature, and pH, bio species present in the seawater can particularly influence the oxygen cathodic reduction reaction and stimulate crevice corrosion process. Specimens with crevice formers were exposed in natural and biological inert seawater. Crevice phenomena were detected by potential versus time measurement and by visual and microscopic observation. In another series of experiments the action of ecological corrosion inhibitors, non‐toxic carboxylic salts, zinc gluconate, and sodium benzoate, has shown the suppression of crevice formation in the seawater.     

The role of structural chemistry in the inhibitive performance of some aminopyrimidines on the corrosion of steel

Corrosion inhibitive performance of 2-aminopyrimidine (APr), 2,4-diaminopyrimidine (dAPr), 2,4-diamino-6-hydroxy-pyrimidine (dAHPr) and 2,4,6-triaminopyrimidine (tAPr) during the acidic corrosion of steel surface was investigated using three methods, MP2, ab initio Hartree-Fock and density functional theory (DFT). Quantum chemical parameters such as the highest occupied molecular orbital energy (E_HOMO), the lowest unoccupied molecular orbital energy (E_LUMO), energy gap (ΔE), dipole moment (μ), sum of the total negative charge (TNC), molecular volume (MV), electronegativity (χ), chemical potential (Pi), global hardness (η), softness (σ) and the fraction of electrons transferred (ΔN), were calculated. Furthermore, the interaction energies of the inhibitors with the iron surface were studied. A good correlation was found between the theoretical data and the experimental results.     

Quantum chemical studies on the corrosion inhibition of some sulphonamides on mild steel in acidic medium

Quantum chemical calculations using the density functional theory (DFT) and some semi-empirical methods were performed on four sulphonamides (sulfaguanidine, sulfamethazine, sulfamethoxazole and sulfadiazine) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies. The results of the quantum chemical calculations and experimental %IE were subjected to correlation analysis and indicate that their inhibition effect are closely related to E_HOMO, E_LUMO, hardness, polarizability, dipole moment and charges. The %IE increased with increase in the E_HOMO and decrease in E_HOMO − E_LUMO. The negative sign of the E_HOMO values and other kinetic and thermodynamic parameters indicates that the data obtained support physical adsorption mechanism.     

Effect of polymeric structure on the corrosion protection of epoxy coatings

Two epoxy resins, EP and EPA, with similar backbone structure but different water affinity, was obtained by curing o-cresol novolac epoxy resin with phenol novolac resin and phenol novolac acetate resin, respectively. By using these two resins, the effect of the polymeric structure on the corrosion protection of the coatings was studied. The free volume in EPA is larger than that in EP as demonstrated by room-temperature density measurement and positron annihilation, while water sorption of EPA is only half of that of EP. Therefore, water affinity of the resin is more important in determining water sorption of the resin than free volume. The cross-sectional area of water passage at coating/metal interface (A_w) was estimated using the electrochemical impedance spectroscopy and compared with that in the resin matrix (A_cs). It was found that, for EPA, A_w is much less than A_cs, which suggests a significant narrowing of water passage at the coating/metal interface. This narrowing of water passage at coating/metal interface due to the formation of a hydrophobic layer can greatly improve the corrosion protection of the coating.     

Effect of thermomechanical treatment on the corrosion of AA5083

Corrosion resistance degradation induced by the presence of β-phase (Al₃Mg₂) limits the performance of aluminum alloy 5083 for some critical applications. The effect of thermomechanical treatment on the corrosion of AA5083 is presented in this paper. The samples subjected to the thermomechanical treatment showed superior corrosion resistance compared to the as-received samples. The effects of grain boundary character distribution, grain shape, texture, and precipitates on corrosion are discussed based on experimental observations. Special boundaries are expected to have a weak effect on the overall corrosion resistance of the material compared to the other factors.     

Effect of the molecular structure on the inhibitor properties of azoles on mild steel corrosion in 1 M hydrochloric acid

Five azoles were investigated as corrosion inhibitors of mild steel in 1 M HCl using gravimetric and polarisation techniques. The chosen azoles have similar chemical structure - their molecules have similar geometry and in an adsorption state almost the same area. The inhibiting properties were found to depend on both the concentration and the molecular structure of the compounds. The adsorption of benzimidazole and 1,3-benzothiazole is described by the Frumkin isotherm, while in the case of 1H-benzotiazole and indole the Langmuir isotherm can be applied. An attempt was made to correlate the inhibitive properties with the electronic structure of the molecules and it was found that the inhibitor properties are connected with the presence of aromatic structure which includes the heterocycle and depend on the number of the lone electron pairs. The HOMO and LUMO energies were calculated and it was found that their values can explain only some features of the observed phenomena.     

Effect of the tetragonal distortion on the electronic structure,phonons and superconductivity in the Mo3Sb7 superconductor

Effect of tetragonal distortion on the electronic structure, dynamical properties and superconductivity in Mo₃Sb₇ is analyzed using first principles electronic structure and phonon calculations. Rigid muffin tin approximation (RMTA) and McMillan formulas are used to calculate the electron–phonon coupling constant λ and superconducting critical temperature. Our results show, that tetragonal distortion has small, but beneficial effect on superconductivity, slightly increasing λ, and the conclusion that the electron–phonon mechanism is responsible for the superconductivity in Mo₃Sb₇ is supported. The spin-polarized calculations for the ordered (ferromagnetic or antiferromagnetic), as well as disordered (disordered local moment) magnetic states yielded non-magnetic ground state. We point out that due to its experimentally observed magnetic properties the tetragonal Mo₃Sb₇ might be treated as noncentrosymmetric superconductor, which could have influence for the pairing symmetry. In this context the relativistic band structure is calculated and spin–orbit interaction effects are discussed.     

建筑结构用耐火耐候钢Q355FRNH耐蚀性能研究

针对钢结构是我国建筑结构的发展趋势,但对其耐火耐蚀性能要求较高的问题,通过添加Cu、Cr、Ni及其他微合金元素,采取控轧控冷工艺,酒泉钢铁集团有限责任公司开发出满足我国西北地区承受温差大、抗冬季除冰盐氯离子腐蚀且具有耐火性能的建筑结构用耐火耐候钢Q355FRNH.通过120 h和240 h干湿交替循环腐蚀试验,发现Q3...     

Mathematical modeling on the corrosion of unprotected structure due to stray current resulting from cathodic protection system

Mathematical modeling on the corrosion of unprotected structures due to a stray current resulting from a nearby cathodic protection system was carried out using the boundary element method. The model consists Laplace’s equation with non-linear boundary conditions (Tafel equations) and the iterative technique to determine the mixed potential of the unprotected structure. The model is applied to an unprotected bare structure as well as a coated structure with several defects. The amount and the location of corrosion along the unprotected structure correlate strongly with experimental results within the experimental conditions studied.     

氧化时间对Ti6Al4V微弧氧化膜结构及耐腐蚀性能的影响

在磷酸盐体系中采用恒压微弧氧化工艺对Ti6Al4V(TC4)合金进行微弧氧化,研究了不同氧化时间对微弧氧化膜层的表面形貌、硬度、粗糙度以及物相生成的影响,并对不同氧化时间的膜层耐腐蚀性能进行了测试。结果表明：随着微弧氧化时间的延长,氧化膜表面微孔径增大,膜层厚度与表面硬度值先增加后又降低,膜层由金红石、锐钛矿及钙磷化合物组成,且主晶相为钙磷化合物,金红石及钙磷化合物含量均随微弧氧化时间的延长而增加;微弧氧化膜层表面Ca/P摩尔比值为1.56,接近人体羟基磷灰石比值,O/Ti原子比值为2.0,膜层表面主要组成为TiO₂;微弧氧化膜层腐蚀电位逐渐减小,腐蚀电流逐渐增大。     

Relation of joint strength and polymer molecular structure in laser assisted metal and polymer joining

The study of laser assisted metal and polymer joining has been conducted to identify the mechanism of the hybrid joint. The bonding mechanism has been revealed to be due to the expansion pressure of pyrolysis fragments. Previous research has dealt with superficial factors without consideration of the polymer thermal decomposition phenomenon, which is the major factor of the joining strength. With experiments and simple chemical analysis for simple structured polymers this paper presents the quantitative relationship among the joint strength, the expansion pressure, the gas fragment composition, and the molecular structure. To verify the relation of the joint strength and the polymer molecular structure, the results were analysed and compared with the results of previous studies. Correlation of the quantified joint strength and the quantified expansion pressure and the monomer yield is also defined. The results confirm that the joint strength is correlated with the polymer structure.     

Impact of gamma-ray-pre-irradiation on the efficiency of corrosion inhibition of some novel polymeric surfactants

The effect of gamma-ray-pre-irradiation on the efficiency of two types of polymeric surfactants, (I and II) as corrosion inhibitors for 304 stainless steel in 2 M hydrochloric acid solution was examined. The inhibition efficiency of the undertaken additives was evaluated using both chemical and electrochemical techniques. The chemical structure of the two polymeric surfactants is illustrated as follows: where MA=maleic anhydride; BP=block polymer of polyoxy ethylene-polyoxy propylene (M.Wt=5000 g mol⁻¹).The obtained corrosion data, indicated that the corrosion inhibition efficiency of the inhibitor (II) was obviously not affected by gamma-ray-irradiation, meanwhile the efficiency of the inhibitor (I) demonstrated a remarkable decrease. Scanning electron microscope (SEM) was used to examine the surface morphology of stainless steel samples after immersion in 2 M HCl solution in absence and presence of the inhibitors at concentration of 400 ppm before and after exposure to gamma-ray-radiation up to a total does of 100 kGy.     

退火温度对磁控溅射TiN/TiCN薄膜残余应力、结构及耐蚀性能的影响

采用反应磁控溅射在AZ31合金上制备了 TiN/TiCN薄膜,并对沉积后的薄膜进行真空去应力退火.分别采用X射线荧光光谱仪(XRF)、扫描电镜(SEM)、掠入射X射线衍射(GIXRD)和电化学工作站对退火前后的薄膜进行表面化学成分、形貌结构、残余应力以及耐蚀性能分析.结果表明:薄膜由FCC结构的TiCN和TiN组成.退...