Da-Hai Xia

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.

Electrochemical noise: a review of experimental setup, instrumentation and DC removal

The electrochemical noise (EN) experiment and instrumentation aspects are briefly summarized, and the direct current (DC) removal methods before EN analysis are illustrated. The results show that poly-nominal trend removal, wavelet analysis and Empirical mode decomposition are effective for DC removal whereas average trend removal and linear trend removal are not suitable for DC removal.

Semiconductivity of steam generator tubing alloys in simulated crevice chemistries containing lead and sulphur

Semiconductivity of passive films on steam generator (SG) tubing alloys, Alloys 690 and 800, in simulated crevice chemistries containing lead and sulphur was investigated using the Mott–Schottky analysis. The interaction of the above species with other ions on the properties of passive film and the correlation between the semiconductivity and the breakdown of passive film were discussed. Experimental results revealed that semiconductivity could be either n or p type semiconductor; both Pb and S can incorporate into the passive layer, depending on the solution pH and alloy compositions. For n type semiconductors formed on Alloy 800, they are easily broken down but more resistant to anodic dissolution; for p type passive films formed on Alloys 690 and 800, they are not easily broken down but more prone to anodic dissolution. It is concluded that the semiconductivity of passive film on SG tubing alloys was dependent on the alloy compositions, the solutions, temperature and film formation potentials.

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.

The Corrosion Behavior of Lacquered Tinplate in Functional Beverage

The deterioration process of the epoxy phenolic coated tinplate in functional beverage was studied by electrochemical impedance spectroscope (EIS). The surface morphology was characterized SPM and SEM. The results showed that corrosion pits were observed on the surface after exposing the coating system to functional beverage for 364 days. The breakages of the organic coating lead to the corrosion of substrate metal. A new parameter p extracting directly from the Bode plot was presented to characterize the deterioration degree of the coating system. Using p value as the discrimination indicator of the deterioration degree of organic coating was presented in this paper.

Detection of the corrosion degree of beverage cans using a novel electrochemical sensor

Purpose – The purpose of this paper is to report a novel electrochemical sensor designed to detect the corrosion of metal cans used for beverage packaging.Design/methodology/approach – Electrochemical impedance spectroscopy (EIS) and electrochemical noise (EN) were performed to detect the corrosion degree of beverage cans that had been stored for 1 month (named s1), 3 months (named s2), 27 months (named s3) and 43 months (named s4).Findings – The EIS results showed that the EIS plot of s1 samples had not developed to a characteristic of two time‐constants, indicating that the coating showed good protective performance. The EIS plots of s2, s3 and s4 showed characteristics of two time‐constants, indicating that the organic coatings of s2, s3, and s4 had lost their protective performance. EN results showed that quantities and amplitudes of transient peaks increased with the increasing storage time, indicating that an increasing degree of local corrosion occurred within the cans. A corrosion process for beve...

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.

Monitoring the Diffusion Layer During Passive Film Breakdown on Alloy 800 with Digital Holography

The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.