Electrochemical Study of Stainless Steel Anchor Bolt Corrosion Initiation in Corrosive Underground Water

Application of low-nickel stainless steel anchor was one of the economical and effective methods to solve the durability problem of slope engineering. At present, there are scarce reports about corrosion characteristics of low-nickel stainless steel in various underground waters. For investigating the corrosion initiation of stainless steel anchor bolt in corrosive underground water, the effect of SO42−, HCO3− and pH value on the corrosion behavior of 201 low-nickel stainless steel was studied via electrochemical methods. As the SO42− concentration, HCO3− concentration or pH value increase, the open circuit potential and polarization resistance increase, while the double-layer capacitance, donor density and passive current density decrease. The results indicate that corrosion is inhibited by SO42−, HCO3− and OH− in underground water. In addition, the inhibitive efficiency of SO42− and HCO3− increases with the SO42− and HCO3− concentration.

Effect of Cathodic Protection on Reinforced Concrete with Fly Ash Using Electrochemical Noise

Corrosion of steel reinforcement is the major factor that limits the durability and serviceability performance of reinforced concrete structures. Impressed current cathodic protection (ICCP) is a widely used method to protect steel reinforcements against corrosion. This research aimed to study the effect of cathodic protection on reinforced concrete with fly ash using electrochemical noise (EN). Two types of reinforced concrete mixtures were manufactured; 100% Ordinary Portland Cement (OCP) and replacing 15% of cement using fly ash (OCPFA). The specimens were under-designed protected conditions (−1000 ≤ E ≤ −850 mV vs. Ag/AgCl) and cathodic overprotection (E < −1000 mV vs. Ag/AgCl) by impressed current, and specimens concrete were immersed in a 3.5 wt.% sodium chloride (NaCl) Solution. The analysis of electrochemical noise-time series showed that the mixtures microstructure influenced the corrosion process. Transients of uniform corrosion were observed in the specimens elaborated with (OPC), unlike those elaborated with (OPCFA). This phenomenon marked the difference in the concrete matrix’s hydration products, preventing Cl− ions flow and showing passive current and potential transients in most specimens.

A Novel Passive Circuit Emulator for a Current-Controlled Memristor

A memristor is an electrical element, which has been conjectured in 1971 to complete the lumped circuit theory. Currently, researchers use memristor emulators through diodes, inductors, and other passive (or active) elements to study circuits with possible attractors, chaos, and ways of implementing nonlinear transformations for low-voltage novel computing paradigms. However, to date, such passive memristor emulators have been voltage-controlled. In this study, a novel circuit realization of a passive current-controlled passive inductorless emulator is established. It overcomes the lack of passive current-controlled memristor commercial devices, and it can be used as part of more sophisticated circuits. Moreover, it covers a gap in the state of the art because, currently, only passive circuit voltage-controlled memristor emulators and active current-controlled emulators have been developed and used. The emulator only uses two diodes, two resistors, and one capacitance and is passive. The formal theory and simulations validate the proposed circuit, and experimental measurements were performed. The parameter conditions of numerical simulations and experiments are consistent. Simulations were performed with an input current amplitude of 15 mA and frequencies of up to 3 kHz and measurements were carried out with an input current amplitude of 0.74 mA and frequency of 1.5 kHz in order to compare with the state of the art.

Improvement of Corrosion Resistance of TiO2 Layers in Strong Acidic Solutions by Anodizing and Thermal Oxidation Treatment

By anodization and thermal oxidation at 600 °C, an oxide layer on Ti with excellent corrosion resistance in strong acid solutions was prepared. The structural properties of TiO2 films before and after thermal oxidation were investigated with methods of Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XRD) and X-ray diffraction (XPS). The electrochemical characterization was recorded via electrochemical impedance spectroscopy, potentiodynamic polarization and Mott–Schottky methods. XRD results show that a duplex rutile/anatase structure formed after oxidation, and the amount of anatase phase increased as the treatment time was prolonged from 3 to 9 h. XPS analysis indicates that as the thermal oxidation time increased, more Ti vacancies were present in the titanium oxide films, with decreased donor concentration. Longer thermal oxidation promoted the formation of hydroxides of titanium on the surface, which is helpful to improve the passive ability of the film. The anodized and thermally oxidized Ti samples showed relatively high corrosion resistance in 4 M HCl and 4 M H2SO4 solutions at 100 ± 5 °C. The passive current density values of the thermally oxidized samples were five orders of magnitude under the testing condition compared with that of the anodized sample. With the oxidation time prolonged, the passive current density decreased further to some extent.