酸腐蚀作用下川渝红层砂岩蠕变特性试验研究

岩石蠕变特性对岩体工程的长期稳定有着重要影响,尤其是在酸雨等水化学作用下,岩石的细观结构遭到破坏,蠕变特性及变形更为显著。以重庆二佛寺红层砂岩为研究对象,通过开展室内三轴压缩分级蠕变试验,研究了酸腐蚀状态下砂岩的蠕变特性。结果表明:酸的腐蚀和浸泡会使砂岩内部孔隙增加,导致砂岩在第一级荷载下会产生较大的瞬时应变和蠕变量,之后瞬时应变量和蠕变量随着应力增加而增大;岩样受到腐蚀软化,蠕变破坏强度为抗压强度的76%,长期强度仅为抗压强度的54%。为了描述蠕变全过程,建立了一个损伤蠕变模型来拟合试验数据,验证了其适用性,可以为岩土工程建设的稳定性提供参考。

酸性干湿循环作用下红砂岩物理力学性能劣化规律

研究干湿循环与酸溶液耦合作用对红砂岩物理力学性质的影响,通过对红砂岩试样进行干湿循环试验、单轴压缩试验、扫描电镜及矿物成分测试,研究不同干湿循环次数和溶液不同pH值下试样的物理力学性质参数、微观结构及矿物成分的变化规律。结果表明:随着干湿循环次数的增加、溶液酸性的增强,试样的质量、纵波波速、弹性模量、单轴抗压强度均呈现差异性衰减的规律,微观结构更加紊乱,矿物成分含量发生改变,这是红砂岩物理力学性能劣化的微观机制。

2,3,5-Triphenyl-2H-tetrazolium Chloride and 2,4,6-Tri（2-pyridyl）-s-triazine on the Corrosion of Mild Steel in HCl

Electrochemical measurement, quantum chemical method, and scanning electron microscopy （SEM） were performed to investigate the inhibitive effect of 2,3,5-triphenyl-2H-tetrazolium chloride （TTC） and 2,4,6-tri（2-pyridyl） -s-triazine（TPT） on the corrosion of mild steel in lmol.L^-1 HCl at room temperature. Impedance spectroscopy measurement showed that the polarization resistance increased and that double layer capacitance decreased with the increase in the inhibitive concentration, and the results of potentiodynamic polarization showed that the inhibitors suppressed both cathodic and anodic processes of steel corrosion without change in the mecha-nism. Higher the orbital density distribution strength of the lowest unoccupied molecular orbital, higher is the molecule dipole, and lower energy gap between the energy of the highest occupied molecular orbital and the energy of the lowest unoccupied molecular orbital resulted in higher inhibitory efficiency. The results of SEM analysis showed that the metal-was protected from aggressive corrosion by the addition of TTC and TPT.

Corrosion inhibition effect of N, N′-bis(2-pyridylmethylidene)-1,2-diiminoethane on AZ91D magnesium alloy in acidic media

The inhibition effect of electrochemical noise, EIS and surface analysis to evaluate N'-bis (2-pyridylmethylidene)- 1,2-diiminoethane (BPIE) Schiff base against AZ91D alloy corrosion in 0.01 mol/L HCl was investigated by different electrochemical methods. Potentiodynamic polarization curves revealed that the BPIE acts as a mixed-type corrosion inhibitor. Electrochemical impedance spectroscopy (EIS) measurements confirmed the corrosion inhibition effect of the BPIE. As the inhibitor concentration increased, the charge transfer resistance increased and the double layer capacitance decreased due to more inhibitor adsorption on the surface. The results obtained by analysis of electrochemical noise (EN) data in time and frequency domains are in good agreement with EIS and polarization results. Moreover, scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) were used to investigate the corrosion inhibition of the BPIE. SEM images showed that the corrosion damage of the alloy surface reduced in the presence of BPIE. The intensity of the XRD peaks corresponding to magnesium-rich α phase increased in the presence of BPIE, indicating lower corrosion of alloy sample. Also, EDX analysis approved the corrosion inhibition performance of the BPIE. The studied Schiff base compound acts by physical adsorption on the alloy surface and its adsorption obeys the Langmuir isotherm.

Inhibition effect of a synthesized N,N′-bis(2-hydroxybenzaldehyde)-1,3-propandiimine on corrosion of mild steel in HCl

The corrosion inhibition of mild steel in 1 mol/L HC1 by N, N＇-bis （2-hydroxybenzaldehyde）- 1, 3-propandiimine （2-HBP） has been investigated by using potentiodynamic polarization, electrochemical impedance spectroscopy （EIS） and chronoamperometry measurements. The experimental results suggest that this compound is an excellent corrosion inhibitor for mild steel and the inhibition efficiency increases with the increase in inhibitor concentration. Polarization curves reveal that this organic compound is a mixed type inhibitor. The effect of temperature on the corrosion behavior of mild steel with the addition of the Schiff base was studied in the temperature range from 25 ℃ to 65℃. The experimentally obtained adsorption isotherms follow the Langmuir equation. Activation and thermodynamic adsorption parameters such as Ea, △H, △S,Kads and AG,ds were calculated by the corrosion currents at different temperatures and using the adsorption isotherm. The morphology of mild steel surface in the absence and presence of 2-HBP was examined by atomic force microscope （AFM） images.

Inhibition effect of 2-amino-5-ethyl-1,3,4-thiadiazole on corrosion behaviour of austenitic stainless steel type 304 in dilute HCl solution

The corrosion inhibition of type 304 austenitic stainless steel by 2-amino-5-ethyl-1, 3, 4-thiadiazole(TTD) compound and the electrochemical behaviour in dilute HCl solution were investigated through potentiodynamic polarization test, mass loss techniques and potential measurements. The results show that the organic derivative is highly effective with a maximum inhibition efficiency of 70.22% from mass loss analysis, while 74.2% is obtained from polarization tests. Observation of the scanning electron micrographs shows the absence of corrosion products due to electrochemical influence of TTD on the surface morphology of the steel. X-ray diffractometry reveals the absence of phase compounds and complexes on the steel samples after exposure. TTD adsorption on the steel surface obeys the Langmuir, Frumkin and Freundlich adsorption isotherms. Corrosion thermodynamic calculations reveal the inhibition mechanism occurs through chemisorption process and results from statistical analysis depict the strong influence of inhibitor concentration on the electrochemical performance of the TTD.

Corrosion inhibition and mechanism of mild steel in hydrochloric acid by ceftriaxone and amoxicillin

Corrosion inhibition of mild steel in 1 mol/L HC1 by amoxicillin and ceftriaxone in the concentration range of 1.00×10^-5-1.00×10^-2 mol/L has been studied using weight loss, electrochemical potentiodynamic polarization, electrochemical impedance spectroscopy （EIS）, scanning electron microscopy （SEM） and quantum chemistry tests at 298 K. The weight loss experiment showed that the inhibition efficiency increased with amoxicillin and ceftriaxone concentrations to attain the maximums of 80.3% and 94.1%, respectively at 1.00×10^-2 mol/L. Potentiodynamic polarization indicated that amoxicillin and ceftriaxone acted as mixed-type inhibitors but mainly inhibited cathode hydrogen evolution reaction for mild steel in 1 mol/L HC1. The electrochemical impedance spectroscopy （EIS） demonstrated the inhibitors covered the active points of metal surface to inhibit corrosion. The absorption of both inhibitors on the mild steel surface was found to follow Langmuir adsorption isothermal and dominantly involve chemical adsorption at 298 K. Scanning electron microscopy （SEM） confirmed both of the inhibitors played a significant protective effect in mild steel corrosion in 1 mol/L HC1. The relationship between the inhibition properties and molecular structure had been discussed by quantum chemistry calculation. All the experimental results concluded that both amoxicillin and ceftriaxone acted as good corrosion inhibitors and their inhibition efficiency was in the order of ceftriaxone 〉 amoxicillin.