Shizhe Song

Corrosion behavior of tinplate in NaCl solution

The corrosion process of tinplate in 0.5 mol/L NaCl solution was investigated using the electrochemical impedance spectroscopy (EIS), and the morphology and structure of the corrosion products were characterized by scanning electron microscope (SEM), scanning probe microscopy (SPM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results showed that the resistance of tin coating, Rc, was essentially constant but the charge transfer resistance, Rct, decreased by 2 orders of magnitude, which indicated that the tin coating was not seriously corroded while the carbon steel substrate was corroded continuously. The corrosion of tinplate in 0.5 mol/L NaCl solution was mainly the dissolution of carbon steel substrate because of the defects in the tin layer and the corrosion product was mainly γ-FeOOH.

Detection of corrosion degradation using electrochemical noise (EN): review of signal processing methods for identifying corrosion forms

Electrochemical noise (EN), as one of the most promising in situ electrochemical methods in corrosion and electrochemical science, has been developing rapidly in recent years with the advancements in instrumentation and signal processing methods. One advantage of EN is its application in long-term or early stage corrosion process monitoring because it instantly detects corrosion rate and corrosion forms. Investigators have applied various mathematical methods to extract characteristic parameters from EN. In this paper, identifying corrosion forms using parameters obtained from time domain, frequency domain and time–frequency domain is reviewed, and the correlation between parameters and corrosion forms is discussed. Finally, other in situ techniques are recommended to be employed synchronously with EN measurement in order to obtain reliable analyses.

Detection of SCC of 304 NG stainless steel in an acidic NaCl solution using electrochemical noise based on chaos and wavelet analysis

The stress corrosion crack (SCC) of 304 nuclear grade (NG) stainless steel (SS) in 0.5 mol/L NaCl+1.5 mol/L H2SO4 was monitored using electrochemical noise (EN) based on chaos theory, statistics and wavelet analysis. The results indicated that the SCC process was divided into three stages according to the transient features in the EN. In the beginning, compared with the sample without applied stress, the enhanced fluctuation amplitude in the electrochemical current noise (ECN) of the stressed samples was attributed to stress-enhanced pitting corrosion and uniform corrosion; then the fluctuations of ECN for all the samples decreased due to a coverage by the corrosion products; however, the ECN fluctuations of stressed sample were larger than the unstressed sample, suggesting that the stress enhanced the SCC initiation and propagation. Chaos analysis revealed that the correlation dimensions increase from 2.1 to 2.5 during the corrosion process, and the applied stress seems increase the complexity and uncertainty of the ECN signal.

Degradation mechanism of lacquered tinplate in energy drink by in-situ EIS and EN

The corrosion process of phenolic epoxy coated tinplate in energy drink was investigated by in-situ electrochemical impedance spectroscopy(EIS) and electrochemical noise(EN) techniques. The experimental results indicate that the degradation process of novolac epoxy coated tinplate in energy drink can be divided into three main stages: organic coating wetted by the beverage; corrosion initiation beneath the organic coating; and corrosion extension process. It was proposed that the tin coating and carbon steel were mainly corroded by organic acids in energy drink through the pores of the organic coating. After the tin coating was corroded, the carbon steel started to corrode due to its higher electrochemical activity and became to be the dominated corrosion reaction.

Sensing Atmospheric Corrosion of Carbon Steel and Low-Alloy Steel Using the Electrochemical Noise Technique: Effects of Weather Conditions

Three electrochemical probes were designed to study the effects of weather on the atmospheric corrosion of carbon steel and low-alloy steel in an urban atmosphere by using the electrochemical noise (EN) technique. The fabricated probes can be successfully applied to investigate instant atmospheric corrosion resistance in various weather conditions. Continuous 15-day EN monitoring showed that, under the same weather conditions, the corrosion resistance of Q235 carbon steel is higher than that of low-alloy steels.

Electrochemical noise monitoring of the atmospheric corrosion of steels: identifying corrosion form using wavelet analysis

ABSTRACT The early stage atmospheric corrosion of T91 and Q235B steels exposed to Tianjin’s urban atmosphere over 20 days was studied using two electrochemical probes via an electrochemical noise (EN) technique. To identify the corrosion process and the corrosion form of the two steels, EN data were analysed by statistics and wavelet transform. The results revealed that the wavelet energy of decomposed EN mainly located at high-frequency level for Q235B steel, whereas it mainly located at the low-frequency level for T91 steel. Analyses of surface images confirmed that Q235B steel underwent uniform corrosion whereas T91 steel suffered from localised corrosion. The obtained noise resistance correlated well with weight loss data. GRAPHICAL ABSTRACT

Detection of SCC on 304 stainless steel in neutral thiosulfate solutions using electrochemical noise based on chaos theory

Purpose This paper aims to investigate the stress corrosion cracking (SCC) process of sensitized 304 stainless steel during the slow strain rate test by using the electrochemical noise (EN) technique. Design/methodology/approach EN data are interpreted based on chaos and wavelet analyses, and correlation dimension and wavelet energy distribution are used as indicators for SCC process identification. Findings Experimental results reveal that the corrosion potential abruptly decreases from 180 to 100 mV at 6,300 s and the current increases from 10 to 100 nA accordingly, which is attributed to passive film breakdown and crack initiation. Chaos and wavelet analyses results reveal that, as crack initiates, the correlation dimensions increase from 1.2 to 1.9, and the corresponding distribution frequencies of maximum relative wavelet energy change from high frequency to low frequency. Originality/value SCC is monitored in lab, and crack initiation and propagation are identified by chaos and wavelet analyses. This work lays the foundation for SCC detection in field using EN.

The potentiostatic-galvanostatic transient response character of a passive system with adsorption

Abstract A kinetic expression of the adsorption-desorption current in potentiostatic-galvanostatic (P-G) measurement was deduced. A mathematical model was set up for the P-G response curve of the passive systems with adsorption. Using a Model SHFF electrochemical transient response instrument, the action of the adsorption inhibitors, piperidine and n -decylamine, on the pitting corrosion of AISI 30455 in 0.5 mol l −1 NaCl solution was examined. The possible mechanism for the inhibition effect on the different stages of pitting process was discussed. The results proved that the new model can represent well the P-G response characteristics of the passive systems with adsorption. Piperidine and decylamine not only block strongly pit initiation, they also retard pit propagation to some extent.

Study on different preparing methods of the metallized fiber core for optical fiber corrosion sensor

Three metallized methods for forming a film on fiber core to monistor corrosion process have been studied and compared. The first one is sputtering nickel controlled by magnetic field under vaccum environment. The second and third is respectively chemically electroplating silver and physical vacuum depositing (PVD) iron. The former two methods aim at forming middle layer for conductive electricity to provide conditions for further electroplating steel. The comparative aspects include electrochemical measurements, such as Cl- affecting on open circuit potential Ecorr and linear polarized resistance Rp. Furtherly, a metallized fiber is prepared to monitor corrosion of ship hull steel, which is approved by scanning electronic microscope and X-ray diffraction analysis. The shifting of output light power displays corrosive process of steel.

Optimal preparing methods for optical fiber corrosion sensing techniques

The feasibility of an optical fiber corrosion sensor(OFCS) is studied in the present paper. A multi-mode fiber is metallised by physical vacuum deposition(PVD) and electroplating a Fe-C alloy film on an uncladded part with 1-2cm length. Comparatively, similar methods used to form metallic film on planar quartz crystal. Electrochemical measurements including continuously inspection of electrochemical parameters show different characters between cylindrical and planar wave guide. The shift of light power transmitted through the fiber is registered with corrosion. Microanalysis is carried out to show the metallised film’s forming. Electrochemical process of the corrosion on the fiber is researched by continuously monitoring open potential Ecorr and linear polarized resistance Rp.