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This study aims to develop a sol-gel-based coating to provide a long-lasting corrosion protection on AZ31 Mg alloy. Silane-based sol-gel coatings have been successfully applied to Mg alloys for corrosion protection. However, the micro or nano defects formed during condensation and solidification will cause the coating failure during a long-lasting immersion in a saline solution. More durable corrosion-protective sol-gel coatings are needed.

A sol-gel-based coating was modified on AZ31 Mg alloy by levodopa (DOPA). The long-lasting corrosion protection mechanism was studied by multiple electrochemical testing methods and surface characterization techniques.

Long-term testing by electrochemical impedance spectroscopy in aqueous 0.1 M NaCl indicated that the modified DOPA@sol-gel coating exhibited significant corrosion protection performance (>14 days). In comparison, the DOPA-free sol-gel coating failed only after three days of testing. The improved corrosion protection is attributed to the self-polymerized DOPA filling to the micro or nano defects in the glassy cross-linked networks of the sol-gel coating, which greatly improves the compactness of the coating.

The method of this study is simple and easy to process, the raw materials are green and the protective effect is excellent, which is of significance for the study of magnesium alloy corrosion protection.

The purpose of this paper was to research the influence of polyaniline/montmorillonite (PANI/OMMT) composite powder content on the corrosion protection of epoxy (EP) coating.

The polyaniline/montmorillonite/epoxy (PANI/OMMT/EP) coatings containing different contents of PANI/OMMT composite powder were prepared on steel. The corrosion protection performances of PANI/OMMT/EP coatings in 3.5 per cent NaCl solutions were investigated by electrochemical impedance spectroscopy. The barrier property of coatings was examined using water absorption analysis. The structure and crosslink density of coatings were examined using scanning electron microscopy and differential scanning calorimetry, respectively.

The PANI/OMMT composite powder could enhance the barrier properties of the EP coating and reduce the corrosion rate of the steel beneath the coating. The coating showed the best corrosion protection performance when 3 per cent PANI/OMMT powder was added to the coating.

The research clarified the influence of PANI/OMMT content on the corrosion protection of coating from two aspects: one is the barrier performance of the coating; the other is the corrosion inhibitors for metal substrate.

This paper aims to prepare a residual rust epoxy coating by adding different quantities of phytic acid (PA) on the surface of the rusty steel and investigate the corrosion protection of PA and its action mechanisms.

A residual rust epoxy coating by adding different quantities of PA was prepared on the surface of the rusty steel. The influence of PA on the corrosion resistance of epoxy-coated rusty steel was investigated by means of electrochemical impedance spectroscopy and adhesion testing.

Results indicated that PA can substantially improve the corrosion resistance of epoxy-coated rusty steel. This improvement is due to the reaction of PA with residual rust and generation of new compounds with protection properties and increased adhesive strength effects on the coating/metal interface. The coating showed better protection performance when 2 per cent PA was added.

Considering the structure of the active groups, PA has strong chelating capability with many metal ions and can form stable complex compounds on the surface of a metal substrate, thereby improving corrosion resistance. In recent years, PA has been reported to be useful in the conversion of coatings or as green corrosion inhibitor. To the best of the authors’ knowledge, few studies have reported the use of PA as a rust converter or residual rust coating. The present work aims to improve the corrosion resistance of residual rust epoxy coating by adding PA.

This paper aim to investigate the influence of PA on the corrosion behavior of carbon steel with blast cleaned or pre-rusted treatments, and interpret the inhibition mechanism of PA on the steel with different surface treatments.

The influence of PA on the corrosion behavior of blast cleaned or rusty steel was investigated by means of electrochemical impedance spectroscopy (EIS). The EIS data were analyzed using the @ZsimpWin commercial software. The morphology and component of steel after immersion were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transformation infrared (FTIR) and X-ray diffractometer (XRD).

EIS analysis results indicated that PA had good corrosion inhibition for blast cleaned or rusty steel. SEM, EDS, FTIR and XRD further indicated that PA had two main corrosion inhibition processes for the corrosion inhibition of blast cleaned or rusty steel: corrosion dissolution and formation of protective barrier layers.

Most published works focus the attention only toward the effect of corrosion inhibitor for the clean metal surfaces. However, the surface condition of metal sometimes is unsatisfactory in the practical application of corrosion inhibitor, such as existing residual rust. Some studies also have shown that several corrosion inhibitors could be applied on partially rusted substrates. These inhibitors mainly include tannins and phosphoric acid, but not PA. Therefore, the authors investigated the influence of PA on the corrosion behavior of carbon steel with blast cleaned or pre-rusted treatments in this paper.

The purpose of this paper is to study the effect of cyclic hydrostatic pressure on the protective performance of cathodic protection (CP) system consisting of Zn‐Bi sacrificial anode and Ni‐Cr‐Mo‐V steel.

The anode and cathode polarization curves of the driving potential and current for CP were investigated in case of cyclic hydrostatic pressure (0‐3.5 MPa) and compared with that at atmospheric pressure. The morphologies of the anode material with and without corrosion products were observed by scanning electron microscopy.

The experimental results revealed that the cyclic hydrostatic pressure had significant influence on the CP system. The anode potential instantaneously responded to the cyclic hydrostatic pressure and the discharge performance decreased due to the deposition of corrosion product. Also, the CP system exhibited higher slope parameter under cyclic hydrostatic pressure, indicating that the CP system cannot provide adequate protection for Ni‐Cr‐Mo‐V steel.

The results presented in this paper clearly show the effect of cyclic hydrostatic pressure on the sacrificial anode CP system, and present a foundation for further research on the practical application of sacrificial anode under cyclic hydrostatic pressure environment.

Steer-by-wire (SBW) system mainly relies on sensors, controllers and motors to replace the traditionally mechanical transmission mechanism to realize steering functions. However, the sensors in the SBW system are particularly vulnerable to external influences, which can cause systemic faults, leading to poor steering performance and even system instability. Therefore, this paper aims to adopt a fault-tolerant control method to solve the safety problem of the SBW system caused by sensors failure.

This paper proposes an active fault-tolerant control framework to deal with sensors failure in the SBW system by hierarchically introducing fault observer, fault estimator, fault reconstructor. Firstly, the fault observer is used to obtain the observation output of the SBW system and then obtain the residual between the observation output and the SBW system output. And then judge whether the SBW system fails according to the residual. Secondly, dependent on the residual obtained by the fault observer, a fault estimator is designed using bounded real lemma and regional pole configuration to estimate the amplitude and time-varying characteristics of the faulty sensor. Eventually, a fault reconstructor is designed based on the estimation value of sensors fault obtained by the fault estimator and SBW system output to tolerate the faulty sensor.

The numerical analysis shows that the fault observer can be rapidly activated to detect the fault while the sensors fault occurs. Moreover, the estimation accuracy of the fault estimator can reach to 98%, and the fault reconstructor can make the faulty SBW system to retain the steering characteristics, comparing to those of the fault-free SBW system. In addition, it was verified for the feasibility and effectiveness of the proposed control framework.

As the SBW fault diagnosis and fault-tolerant control in this paper only carry out numerical simulation research on sensors faults in matrix and laboratory/Simulink, the subsequent hardware in the loop test is needed for further verification.

Aiming at the SBW system with parameter perturbation and sensors failure, this paper proposes an active fault-tolerant control framework, which integrates fault observer, fault estimator and fault reconstructor so that the steering performance of SBW system with sensors faults is basically consistent with that of the fault-free SBW system.