Xingpeng Guo

Effects of direct current electric field on corrosion behaviour of copper, Cl− ion migration behaviour and dendrites growth under thin electrolyte layer

Abstract Effect of direct current electric field (DCEF) on corrosion behaviour of copper printed circuit board (PCB-Cu), Cl− ion migration behaviour, dendrites growth under thin electrolyte layer was investigated using potentiodynamic polarization and scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS). Results indicate that DCEF decreases the corrosion of PCB-Cu; Cl− ions directionally migrate from the negative pole to the positive pole, and enrich on the surface of the positive pole, which causes serious localized corrosion; dendrites grow on the surface of the negative pole, and the rate and scale of dendrite growth become faster and greater with the increase of external voltage and exposure time, respectively.

Electrochemical corrosion behaviour of copper under periodic wet–dry cycle condition

Abstract The effects of the dry period, temperature and (NH4)2SO4 on the electrochemical corrosion behaviour of copper film in printed circuit board (PCB–Cu) under thin electrolyte layer were investigated by electrochemical noise and electrochemical impedance spectroscopy combining with SEM analyses under various periodic wet–dry cycle conditions. Results showed that the corrosion rate of PCB–Cu decreased at the initial stage then increased, and eventually attained a steady state at the last stage, which could be ascribed to the difference of the protective performance of the formed corrosion products. According to the characteristics of the noise potential, each single wet–dry cycle could be divided into three regions.

The Protection Performance of Polypyrrole Coating Doped with Different Counter Anions for the Corrosion of NiTi Alloy

The electrochemical corrosion behavior of NiTi alloy electrodeposited conductive polypyrrole (PPy) coatings doped with small size sulfate (SO42  ), medium size para-toluene sulfonate (pTS  ) and large size dodecylbenzene sulfonate (DBS  ) counter anions has been studied by electrochemical measurements and surface analysis. It is demonstrated that PPy coatings inhibit the corrosion of NiTi substrate in chloride solution by shifting the corrosion potential and pitting potential positively and increasing the impedance of corrosion process. The protective performance of PPy coatings for NiTi alloy is in the order: PPy/pTS < PPy/SO4 < PPy/DBS. The protective performance of the doped PPy coatings for NiTi alloy is related to their anions exchange abilities. The worse anion exchange ability PPy coating has, the better protective performance. The increase of solution pH increases the corrosion rate of the coated NiTi substrate.

Comparison of polynomial fitting and wavelet transform to remove drift in electrochemical noise analysis

Abstract Polynomial fitting and wavelet transform, which could be used to remove trends of electrochemical noise (EN), have been compared in this paper. The typical pitting EN records were chosen to study the effects of these two methods on statistical parameters, power spectral density (PSD), whole energy distribution plot (WEDP) and relative energy distribution plot (EDP), while the indication of selecting the appropriate method was put forward. The results show that for the calculation of the statistical parameters, the polynomial with m<5 and wavelet removal methods all could be selected. Power spectral density plots and WEDPs indicate that the higher order polynomial and wavelet removal methods would reduce the low frequency signals more heavily, so lower order (m=1–3) polynomial is recommended. The appearance of plateau in low frequency part of PSD plots could be regarded as the indication of the best selection of m. Combined EDPs with the analysis of the EN time records, the best m could also be selected, and its value might be just as the same as that obtained from PSD results. In general, the polynomial detrending is a more suitable and flexible trend removal method.

Na2S-influenced electrochemical migration of tin in a thin electrolyte layer containing chloride ions

Sodium sulfide was used to prevent the formation of dendrites during the electrochemical migration of tin in chloride-containing thin electrolyte layers. This investigation was based on in situ electrochemical and optical techniques, as well as ex situ characterization. Results show that sodium sulfide can inhibit the electrochemical migration behavior of tin by precipitating tin ions on the anode side, and the inhibition effect strongly depends on concentration. The effects of an applied bias voltage and pH alterations in the system caused by Na2S hydrolysis were also studied. Proposals were made for the mechanisms involved to explain the role of sodium sulfide.

Study of inhibition performance and adsorption behaviour of lauric acid on N80 steel in acidic and near neutral environments

Abstract Inhibition performance and adsorption behaviour of lauric acid in acidic and near neutral environments were investigated by electrochemical and surface analysis methods. The results showed that the inhibition ability and the minimum effective inhibitor concentration are both pH dependent. The former decreased and the latter increased with pH value. The adsorption of the inhibitor was the predominant mechanism at lower pH values, with the formation of a protective adsorption film. At higher pH value, the inhibitor cannot prevent the corrosion process effectively and hence the adsorption of the inhibitor and formation of FeCO3 like corrosion product coexisted. The difference of inhibition performance can be ascribed to the different adsorption state of the inhibitor on metal surface at different pH value resulting in a different interaction with the metal surface, which was validated by vibrational spectroscopy (attenuated total reflection Fourier transform infrared spectroscopy).

Effect of Hydrodynamics on the Inhibition Effect of Thioureido Imidazoline Inhibitor for the Flow Accelerated Corrosion of X65 Pipeline Steel

Effect of hydrodynamics on the inhibition effect of thioureido imidazoline inhibitor (TAI) for the flow accelerated corrosion (FAC) of X65 carbon steel elbow was studied by electrochemical measurements and surface characterization by placing array electrodes at different locations on the elbow. Compared to static condition, the inhibition efficiency of TAI for FAC is relatively low as a result of drastic turbulence flow and high wall shear stress during the FAC test. The inhibition efficiency at the outer wall is higher than that at the inner wall, which is associated with the higher flow velocity, shear stress, and turbulent kinetic energy at the inner wall of the elbow. The distribution of inhibition efficiency is in good agreement with the distribution of hydrodynamic parameters at the elbow.

The Effect of Tellurium on the Al–Zn–In Anode

The effects of tellurium as the alloying element on the Al―Zn―In sacrificial anodes have been investigated in NaCl solution. Scanning electron microscopy, energy-dispersive x-ray analysis, and inductively coupled plasma mass-spectrometry have been employed to study the morphology and corrosion behavior of improved anodes. The corrosion of the Al―Zn―In―Te anode initiates at the segregations where Te is enriched. With the addition of Te as the alloying element, the Al―Zn―In anodes exhibit lower harmful impurity content, inhibition of self-corrosion, and higher current efficiency, which are desirable for sacrificial anodes.

Study of Flow-Assisted Corrosion of AZ91D Magnesium Alloy in Loop System Based on Array Electrode Technology

A loop system was used to investigate flow-assisted corrosion (FAC) of AZ91D magnesium alloy at an elbow based on array electrode technology by potentiodynamic polarization, computational fluid dynamics, simulation and surface analysis. The experimental results demonstrate the fluid hydrodynamics plays a significant role in the FAC of AZ91D magnesium alloy. The corrosion rate increases from the outer wall to the inner wall of the elbow, with the higher corrosion rate corresponding to the higher flow velocity and larger shear stress at the elbow. The maximum corrosion rate appears at the innermost wall of the elbow, the location with the maximum flow velocity and shear stress.

Atomic force microscopy and electrochemical investigation on the corrosion behavior of carbon steel passivated by molybdate and chromate

The effects of CrO42− and MoO42− ions on the corrosion behavior of carbon steel in 0.5 M NaCl solution have been studied using electrochemical measurements and atomic force microscopy. The results suggest that both ions have good inhibition effects on the general and pitting corrosion of carbon steel. At the same concentration, the inhibition efficiency of CrO42− is higher than that of MoO42−. The passive film formed by CrO42− is also much harder than that formed by MoO42−. The passive films formed by both ions are nonconductive. Microsc. Res. Tech., 2013.