Papers by Keyword: Open Circuit Potential (OCP)

Abstract: This study investigates the corrosion resistance of Stainless Steel 201 through varying surface treatments and testing in a 3.5 wt% NaCl solution, mimicking seawater conditions. Given its prevalent use in industries like oil, Stainless Steel 201's resistance to pitting corrosion is crucial, primarily when used in pipes. The research employs electrochemical techniques, specifically Cyclic Voltammetry and Immersion, to treat the material's surface. The surface treatment using citrict acid (C₆H₈O₇) varying the concentration of 1, 1.5, and 2 M. Corrosion tests utilize open circuit potential, anodic polarization patterns, and characterization via optical microscopy and SEM-EDS. Results indicate that the material subjected to a Cyclic Voltammetry treatment with 2M citric acid exhibited the lowest corrosion rate at 0.001243 mmpy, with 21 instances of pitting corrosion. Conversely, untreated Stainless Steel 201 showed a higher corrosion rate of 0.006177 mmpy and 87 instances of pitting corrosion. This underscores the significant improvement in corrosion resistance achieved through the specified surface treatment, highlighting its potential value for enhancing Stainless Steel 201's longevity and performance in corrosive environments. Keywords: Stainless Steel 201, Cyclic Voltammetry, Immersion, Open Circuit Potential (OCP), Anodic polarization Patterns, Corrosion Rate, Pitting Corrosion.

Abstract: In this investigation, the resistance of brass material to stress corrosion cracking (SCC) in a chloride solution was assessed through adjustments in temperature (25°C, 35°C, and 45°C) and bending angles of the brass material (1.0 wt%, 2.0 wt%, and 3.5 wt%). The chosen solution closely resembles saltwater, making it suitable for testing, especially considering the widespread use of brass materials in various industrial sectors, particularly shipping. Stress corrosion cracking tends to impact brass materials under heavy loading. The primary objective of this study is to characterize the corrosion rate of brass materials. The method involved a bending test with angle variations of 180°, 90°, and 0°. Corrosion assessment utilized the Open Circuit Potential method, Anodic Polarization Tafel, and a digital microscope for the material's microstructure properties. According to the findings, brass material exhibits the lowest corrosion rate (10 x 10^-6 mmpy) at a temperature of 25°C distilled water and an angle variation of 0°. Conversely, the corrosion rate increases with variations in bending angle, temperature, and the concentration of NaCl solution, as evidenced by the corrosion rate of 28.035 x 10^-5 mmpy with an angle variation of 180°, to a corrosive solution of NaCl 3.5 wt% at a temperature of 45°C.

Abstract: Austenitic stainless steels especially 316L has been used extensively in many sectors including construction, medical and household appliances due to their highly resistance to corrosion attack, reasonable cost and excel in mechanical properties. However, in corrosive media, 316L are susceptible to localised corrosion attack especially in seawater and high temperature. The corrosiveness of media increased as the anions contents increased. This paper presents the corrosion mechanism of 316L exposed to high concentration of sulphate in the salinity of seawater. The solution (media) was prepared according to the same composition as seawater including pH, salinity and dissolved oxygen. The corrosion mechanism were characterized to breakdown potential (E_b) of 316L which are the potential once reaches a sufficiently positive value and also known as pitting potential. This is the most point where localized corrosion susceptibility to evaluate and considered a potential, which could be an appropriate point according to any given combination of material/ambient/testing methods. The E_b value were identified at 4°C, 20°C, 50°C and 80°C and compared with E_b value of 316L in seawater. The E_b value of 316L in high sulphate are higher compared to seawater in every temperature which elucidate that some anions accelerate corrosion attack whereas some anions such as sulphate behaves as inhibiting effect to 316L.

Abstract: In this paper, a study on the electrochemical behaviour and electrical properties of Al-Zn and Al-Zn-Sn alloys in tropical seawater using open circuit potential (OCP) measurement and electrochemical impedance spectroscopy (EIS) are reported. The results from both the OCP and EIS tests show that surface activation was observed in the Al-Zn alloy with the addition of 1.34 wt.% Sn which can be manifested by the shift of OCP values towards more electronegative direction. The EIS spectra of Al-Zn alloy exhibits a semicircle loop, while the EIS spectra for the Al-Zn-Sn alloy exhibits a semicircle with a semicircle inductive loop. The change in EIS spectra for Al-Zn-Sn alloy is correlated to the increase of surface activation resulting in a less stable passive layer. Equivalent circuits models were proposed to fit the impedance spectra and the corresponding electrical parameters with optimum values were deduced. The modulus impedance in the low frequency region or polarization resistance, R_pol obtained for the Al-Zn-Sn alloy, R_pol = 2.76 kΩ cm²) is slightly decreased compared to the corresponding value of the Al-Zn alloy, R_pol = 3.97 kΩ cm²), indicating a considerable reduction in the protective capability of the oxide layer on the Al-Zn-Sn alloy. It appears that the heterogeneous oxide film and pores formed on the Al-Zn-Sn alloy play a key role in reducing total resistance to the flow of electron at the alloy-electrolyte interface.