한국부식방식학회

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MoS2 코팅된 치과용 임플란트의 표면특성과 생체적합성
The Ti-6Al-4V alloy is widely used as an implant material due to its higher fatigue strength and strengthto-weight ratio compared to pure titanium, excellent corrosion resistance, and bone-like properties that promote osseointegration. For rapid osseointegration, the adhesion between the titanium surface and cellular biomolecules is crucial because adhesion, morphology, function, and proliferation are influenced by surface characteristics. Polymeric peptides and similar coating technologies have limited effectiveness, prompting a demand for alternative materials. There is growing interest in 2D nanomaterials, such as MoS2, for good corrosion resistance and antibacterial, and bioactive properties. However, to coat MoS2 thin films onto titanium, typically a low-temperature hydrothermal synthesis method is required, resulting in the synthesis of films with a toxic 1T@2H crystalline structure. In this study, through high-temperature annealing, we transformed them into a non-toxic 2H structure. The implant coating technique proposed in this study has good corrosion resistance and biocompatibility, and antibacterial properties.
KEYWORDs : Dental Implant, MoS2 Surface coating, Corrosion resistance, Biocompatibility, Ti-6Al-4V
AUTHORs : 권민기 · 이준식 · 김미은 · 최한철†

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열처리에 따른 무전해 니켈 도금 층의 상변태 거동이 부식과 캐비테이션 침식에 미치는 영향
The objective of this study was to investigate corrosion and cavitation-erosion characteristics of the electroless nickel plating layer with heat treatment. The crystallization temperature of the electroless nickel plating layer was about 410 oC. The phase transformation energy was confirmed to be 12.66 J/g. With increasing heat treatment temperature, the amorphous electroless nickel plating layer gradually changed to crystalline Ni and Ni 3 P. At the same time, the crystal grain size was also increased. Additionally, when heat treatment was performed at a temperature above 400 oC, NiO phase was observed due to oxidation phe-nomenon. As a result of the electrochemical polarization experiment, the corrosion resistance of the heattreated electroless nickel plating layers was superior to that of the as-deposited plating layer. This was because crystal grains became larger and grain boundaries decreased during heat treatment. The cavitationerosion resistance of heat-treated plating layers tended to be superior to that of as-deposited plating layers due to increased microhardness.
KEYWORDs : Electroless nickel plating, Corrosion, Cavitation-erosion, Phase transformation, Heat treatment
AUTHORs : 박일초 · 김성종†

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Characterizations of Precipitated Zinc Powder Produced by Selective Leaching Method
This work investigated the influence of concentration and applied potential on the characteristics of zinc powder (purity, apparent density, morphology, particle size distribution, and particle zeta potential) produced by the electrochemical process from waste brass. High-purity zinc powder is obtained using selective leaching of industrial brass waste in acidic, neutral, and alkaline solutions. The free immersion method with and without voltage using linear polarization technique is used. In the electrochemical process, hydrochloric acid HCl in three different concentrations (0.1, 0.2, and 0.3) M is used. The time and the distance between the electrodes are set to be 30 min and 3 cm, respectively. It has been found that the percentage purity is 98%, 96%, and 94% for the acidic, neutral, and alkaline solutions, respectively. In addition, the morphology of zinc powder analyzed by SEM was dendritic and mossy. It has been recorded that the purity of zinc increases with the increase of the concentration and applied potential. The highest value of purity for zinc powder was %98.58 in 1000 mV and 0.3M concentration for graphite cathode.
KEYWORDs : Brass alloy, Selective leaching, Dezincification corrosion, Linear polarization and Purity
AUTHORs : Marwa F. Abd, F. F. Sayyid†, and Sami I. Jafar Al-rubaiey

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Nano-engineering of Hybrid Titanium Oxide Structure (TiO2) using Pore-widening Concentration for Enhanced Superhydrophilicity
Titanium alloy is gaining attention in the medical industry due to its excellent biocompatibility and osteoconductivity. However, the natural oxide film on the titanium surface is insoluble, resulting in inadequate bone adhesion. Therefore, it is necessary to optimize the contact between biological tissues and implant surfaces, and alter the chemical composition and morphological characteristics of the implant surface. In this study, the anodization method was applied to titanium surface treatment to form a uniform and robust oxide film. Subsequently, a chemical process, pore-widening, was employed to change the morphological characteristics of the oxide film. The concentration of the pore-widening solution was varied at 2, 4, 6, and 8 wt% and the process time was set at 30 and 60 minutes. As the concentration of the pore-widening solution increased the pore diameter of the oxide film increased. Notably, at 6 wt% for 60 minutes, the oxide film exhibited a coexistence of pillars and pores. Based on this, it was determined that surface roughness increased with higher concentration and longer process time. Additionally, the presence of pillars and pores structures maximized hydrophilicity. This study provides insights into enhancing the surface properties of titanium for improved performance in medical implants.
KEYWORDs : Anodization, Pore-widening concentration, Titanium, Hybrid titanium oxide nanostructure, Superhydrophilicity
AUTHORs : Yeji Choi and Chanyoung Jeong†

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The Effect of Mo Addition on Oxygen Vacancies in the Oxide Scale of Ferritic Stainless Steel for SOFC Interconnects
The concentration and diffusion coefficient of oxide ion vacancies in the oxide scale formed on Fe-22Cr-0.5Mn ferritic stainless steel with and without molybdenum (Mo) was measured at 800 °C by the electrochemical polarization method. After pre-oxidation for 100 h in ambient air at 800 °C, the oxide scale on one side was completely removed with sandpaper. A YSZ plate was placed on the side where the oxide scale remained. Platinum (Pt) meshes were attached on the top of the YSZ plate and the side where the oxide scale was removed. Changes in electrical current were measured after applying an electrical potential through Pt wires welded to the Pt meshes. The results were interpreted by solving the diffusion equation. The diffusion coefficient and concentration of oxide ion vacancy decreased by 30% and 70% in the specimen with Mo, respectively, compared to the specimen without Mo. The oxide ion vacancy concentration of chromia decreased due to the addition of Mo.
KEYWORDs : Stainless steel, Solid oxide fuel cell, Interconnect, Molybdenum, Oxidation
AUTHORs : Dae Won Yun†, Hi Won Jeong, Seong Moon Seo, Hyung Soo Lee and Young Soo Yoo

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Comprehensive Analysis of the Corrosion Inhibition Performance of 4-Piperonylideneaminoantipyrine for Mild Steel in HCl Solution: Concentration, Time, Temperature Effects, and Mechanistic Insights
Metal corrosion in acidic environments is a major issue in various industrial applications. This study evaluates the 4-piperonylideneaminoantipyrine (PPDAA) corrosion inhibition efficiency for mild steel in a hydrochloric acid (HCl) solution. The weight loss method was used to determine the corrosion inhibition efficiency at different concentrations and immersion time periods. Results revealed that the highest inhibition efficiency (94.3%) was achieved at 5 mM concentration after 5 hours of immersion time. To inspect the surface morphology of the inhibitor film on the mild steel surface, scanning electron microscopy (SEM) was used before and after immersion in 1.0 M HCl. Density functional theory (DFT) calculations were performed to investigate the molecular structure and electronic properties of the inhibitor molecule to understand the corrosion inhibition mechanism. Theoretical results showed that the inhibitor molecule can adsorb onto the mild steel surface through its nitrogen and oxygen atoms, forming a protective layer that prevents HCl corrosive attack. These findings highlight the potential of PPDAA as an effective corrosion inhibitor for mild steel in HCl solution. Moreover, combining experimental and theoretical approaches provides insights into the mechanism of corrosion inhibition, which is essential for developing effective strategies to prevent metal corrosion in acidic environments.
KEYWORDs : Corrosion inhibition, 4-(Piperonylideneamino)antipyrine (PPDAA), Mild steel, Hydrochloric acid (HCl), Density functional theory (DFT)
AUTHORs : Ahmed Y. I. Rubaye, Sabah M. Beden, Ahmed A. Alamiery†, A. A. H. Kadhum, Waleed K. Al-Azzawi

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Corrosion Behavior of Fe-Ni Bainitic Steel Through an Inverted Austempering Multi-Step Process for Weathering Steel Applications
A Fe-Ni Bainitic steel as a weathering steel application was developed by combining its excellent mechanical properties and corrosion resistance in maritime environments. Nickel concentration (0.4-3 wt%) and inverted austempering multi-step (IAM) process were primary determinants of the microstructure of the Fe-Ni Bainitic steel. The initial austempering steel was performed at 300 o C for 600 seconds to obtain a partly bainitic transformation. The steel was heated again for 1800 s at 450 o C. The microstructure was comprised of ferrite, a blocky martensite/austenite island, and a homogeneous lath-shape bainite structure with widths ranging from 4.67 to 6.89 µm. The maximum strength, 1480 MPa, was obtained with 3 wt% nickel. In this study, corrosion behavior was investigated utilizing potentiodynamic and electrochemical impedance spectroscopy (EIS) tests. A higher nickel content in Fe-Ni Bainitic steel refined the grain size, improved the bainite fraction, lowered the corrosion rate to 0.0257 mmpy, and increased the charge transfer of film resistance to 1369 Ω.
KEYWORDs : Inverted austempering multi-step process, Marine environment, Fe-Ni steel, Weathering steel
AUTHORs : Miftakhur Rohmah†, Gusti Umindya Nur Tajalla, Gilang Ramadhan, Yunita Triana, and Efendi Mabruri

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Methods of Improving Operational Reliability of Oil Well Casing
Oil well casing leak is caused by contact of casing outer surface with formation electrolyte. It is usually associated with an aquifer with a high salt content or absence of a cement ring behind the casing. The only way to reduce external casing corrosion is through cathodic protection. Through cathodic polarization of casing structure, electron content in crystal lattice and electron density will increase, leading to a potential shift towards the cathodic region. At Tatneft enterprises, cathodic protection is carried out according to cluster and individual schemes. The main criterion for cathodic protection is the size of protective current. For a casing, the protective current is considered sufficient if measurements with a two-contact probe show that the electric current directed to the casing has eliminated all anode sites. To determine the value of required protective current, all methods are considered in this work. In addition, an analysis of all methods used to determine the minimum protective current of the casing is provided. Results show that the method of measuring potential drop along casing is one of the most reliable methods for determining the value of protective current.
KEYWORDs : Corrosion, Cathodic protection, External casing, Profile of the voltage drop, Distribution of currents along the depth
AUTHORs : Sergey A. Dolgikh, Irek I. Mukhamatdinov†

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