Development of a Wireless Corrosion Detection System for Steel-Framed Structures Using Pulsed Eddy Currents

Structural health monitoring (SHM) can be more efficient with the application of a wireless sensor network (WSN). However, the hardware that makes up this system should have sufficient performance to sample the data collected from the sensor in real-time situations. High-performance hardware can be used for this purpose, but is not suitable in this application because of its relatively high power consumption, high cost, large size, and so on. In this paper, an optimal remote monitoring system platform for SHM is proposed based on pulsed eddy current (PEC) that is utilized for measuring the corrosion of a steel-framed construction. A circuit to delay the PEC response based on the resistance–inductance–capacitance (RLC) combination was designed for data sampling to utilize the conventional hardware of WSN for SHM, and this approach was verified by simulations and experiments. Especially, the importance of configuring sensing modules and the WSN for remote monitoring were studied, and the PEC responses caused by the corrosion of a specimen made with steel were able to be sampled remotely using the proposed system. Therefore, we present a remote SHM system platform for diagnosing the corrosion condition of a building with a steel structure, and proving its viability with experiments.

Corrosion Behavior of Copper Bearing Steels and the Derived In-Situ Coating

Using a period immersion wet/dry cyclic corrosion test, in-situ copper-coated steels prepared by corroding copper-bearing steels were investigated in this study. The steel with a higher copper content (>3%) has a higher initial corrosion rate due to its obvious two-phase microstructure. The corrosion rates of all copper bearing steels tend to be stable after a certain time of corrosion. A copper-rich layer is formed between the matrix and the rust layer, which is due to the diffusion of copper from the rust layer to the metal surface. The copper’s stability under this corrosion condition led to the formation of a thin copper-rich film, which was uncovered after removing the rust by choosing appropriate descaling reagents. The copper coating was generated from the matrix itself during the corrosion process at 25 °C, which provided a new approach for producing in-situ composite materials without any bonding defect. It is found that the corrosion rate, corrosion time, and copper content in steel all affect the formation of copper-rich layer. In addition to the noble copper surface, the electrochemical corrosion test results show that the corrosion resistance of copper-coated steel has been significantly improved.

TECHNOLOGY PROVIDING SECONDARY PROTECTION METAL STRUCTURES AGAINST CORROSION UNDER AGGRESSIVE IMPACT OF METALLURGICAL PRODUCTION

Research is aimed at the formation and development of innovative developments to increase the metal structures corrosion protection, as an important means of ensuring the quality and safety industrial facilities. The method determining the corrosion destruction signs, the procedure of monitoring and carrying out measures to diagnose the technical condition of lattice metal structures according to the level of corrosion hazard were adopted. The nomenclature indicators and control methods (conformity assessment) of determining parameters primary and secondary protection metal designs against corrosion is established. During this study, the lattice structures operational condition loader crane’s girder structure was considered. It is revealed that operation of the crane is carried out in difficult production conditions operating environment’s aggressive influence in combination with considerable dynamic loadings working operations loading technological process, unloading, sorting (averaging) of ore yard’s charge of blast furnace shop. Based on the study structures corrosion condition and operating conditions, measures have been developed to increase the durability ore-grab crane of the reloader. Based on the analysis of the principles of the ISO 9001 process approach, the development and implementation design solutions to extend the structures service life in aggressive environments of metallurgical production. It is proved that the procedure of making constructive and technological decisions, performance works on increase corrosion resistance promotes maintenance conditions of resource saving and technological safety industrial constructions. The principles process is offered to develop and implement design measures to extend the service life of structures in aggressive environments metallurgical production are proposed. Constructive and technological measures to ensure durability in accordance with the requirements of the building structure corrosion risk have been developed, which are determined by the critical indicators metal structures protection in the conditions corrosion influences within their limit values.

Corrosion Resistance of Industrial Pure Titanium and its Alloys under High Temperature and Different Cooling Methods

Industrial pure titanium (TA2) and Ti-6Al-4V (TC4) have been widely available for chemical equipment. However, the corrosion resistance changes during their post-fire performance. In this research, the electrochemical properties of industrial pure titanium and Ti-6Al-4V after heat treatment and different cooling methods were analyzed by AC impedance technique and dynamic polarization method. The results support two conclusions. Firstly, when the temperature is approximate to the phase transition point, for pure titanium and its alloys, water-cooling can obtain better corrosion resistance than air-cooling. With regard to pure titanium, its best corrosion resistance can be obtained at 800°C under water-cooling. For Ti-6Al-4V, its best corrosion resistance can be obtained when the temperature reached 910 °C under water cooling condition. Secondly, the corrosion current density under acid corrosion condition has risen compared with neutral corrosion condition. These results can provide some experimental data and theoretical basis for post-fire anticorrosion performance of titanium materials, and also support the safety, risk evaluation of titanium equipment.

Fatigue Assessment of Mooring Chain Considering the Effects Of Mean Load and Corrosion

Results from full scale fatigue tests of offshore mooring chains performed in recent years have revealed considerable influence of both mean load and corrosion condition on the fatigue capacity. It has been shown that a reduction of the mean load gives an increase in fatigue life, whereas the corrosion experienced by used chains have a significant negative impact. Neither of these effects are properly addressed by current S-N design curves or design practice. This paper suggests an extended S-N curve formulation, that includes the effects of mean load and corrosion condition. The parameters of the extended formulation are estimated empirically from mooring chain test data that includes new and used chains, with various mean loads and with different degrees of corrosion. The fitted capacity model is then used for fatigue calculation for the mooring system of a semi-submersible, showing the importance of using realistic mean loads and mooring chain corrosion in fatigue assessments.

Non-Destructive Investigation of a 44-Year-Old RC Structure Exposed to Actual Marine Tidal Environments Using Electrochemical Methods

Investigation of deterioration progress in marine structures without destroying them is crucial as early detection of damage before applying the suitable remedial measures. This study presents a series of non-destructive assessment on a 44-year-old naturally corroded RC structure exposed to marine tidal environments using observation of defective appearances and electrochemical tests. The visual observation was conducted by inspecting the corrosion condition of steel bars, crack patterns, and the spalling of concrete cover. The electrochemical investigations carried out in this research consisted of the half-cell potential mapping, the electrical resistivity of concrete, and the corrosion rate of steel bars. The results revealed that electrochemical test results conducted in this research were in good agreement with the actual deterioration degree checked by defective appearances. The RC structure was categorized as Grade II-1 (first half of the acceleration stage). Based on the deterioration degree, both applications of small direct current to control the potential of steel bars in immunity condition and patch repair method by removing the chloride contaminated concrete were recommended as appropriate repairing strategies, and they could extend the service life the of structure.