Purpose
When concrete is manufactured, it can be instantaneously contaminated by chloride (Cl−) ions or later by their intrusion from the environment. This work aims to study the electrochemical behavior of the passive layer formed on the reinforcing steel surface in the presence of the same Cl− ion concentration, with and without passivation time. This will, undoubtedly, affect the corrosion threshold values thereafter.
Design/methodology/approach
Electrochemical polarizations were carried out in two concrete pore solutions. The surfaces of samples immersed for 255 days in saturated Ca(OH)2 solution were examined with optical and scanning electron microscopy and Raman microspectroscopy.
Findings
Cl− ion origins in reinforced concrete lead to different values of corrosion thresholds. The passive layer behaves like a physicochemical barrier, and corrosion occurs at higher NaCl concentration thresholds. The formed passive film on the steel surface shows differences in the chemical composition and the morphology. The results show a rich presence of hematite. Maghemite, lepidocrocite, akaganeite and goethite are also present in much lower concentrations. The Cl− ion presence in fresh concrete at the beginning of the manufacture harms the good formation and the good stability of these oxides, leading to corrosion initiation.
Originality/value
This study contributes to a better understanding of the passive layer role, not only in reducing the corrosion rate value but also in reconsidering new Cl− ion corrosion threshold values.
Losing a lot of blood during surgery using a conventional scalpel is something that is highly avoided. The purpose of this study is to replace the conventional scalpel with a tool that utilizes a high frequency whose duty cycle is regulated and then centered at one point. Researchers take advantage of the effect of heat generated by high frequencies which are centered at one point so that it can be used for the process of surgery and coagulation in body tissues so as to minimize the occurrence of a lot of blood loss. Researchers use a high frequency of 350 KHz which is set with a duty cycle of 6% on 94% off and is equipped with 3 levels of power selection and uses forceps as a medium to concentrate high frequencies at one point. The module design consists of a 350 KHz frequency generator, a pulse control circuit to adjust the duty cycle, a power control circuit as a power setting, a driver circuit to combine the frequency with the set power so that different outputs are obtained according to the settings, and an inverter circuit to increase the voltage. In this study, after measuring using an oscilloscope in the driver circuit, the average output amplitude at each low, medium, and high setting was 27.25 Vpp, 28 Vpp, and 28.625 Vpp. The results showed that the bipolar electrosurgery unit (coagulation) module as a whole can replace conventional scalpels so that it can minimize the occurrence of a lot of blood loss during surgery. However, the frequency generator and power selection need to be improved.
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