• Journal of Welding and Joining
• /
• 제4권3호
• /
• pp.58-71
• /
• 1986

Mechanical and corrosion property of duplex stainless steel weldments made by the GTAW and SMAW process were studied. Fracture toughness, general and local corrosion resistance of GTAW and SMAW weldments were evaluated in terms of Charpy V notch impact test, anodic polarization diagram, pitting corrosion rate, respectively. SMA weld metal showed much lower impact toughness and higher ductile-brittle transition temperature than GTA weld metal. Fractographic and EDX analysis on fracture surface of SMA weld metal demonstrated the existence of (Si, Ti), oxide in large amounts. Potentiodynamic anodic polarization diagram of GMA weld metal showed much lower passive current density than SMA weld metal in 4% $H_2/SO_4$ solution. And pitting corrosion rate test showed the same tendency. Relating the microstructure, chemistry and property, it can be concluded that GTA weld metal gives better toughness due to lower oxygen content, i.e. lower inclusion content, and better corrosion resistance due to higher Pitting Index(PI) than SMA weld metal.

• 한국정밀공학회지
• /
• 제23권4호
• /
• pp.146-152
• /
• 2006

In micro electrochemical machining (ECM), electrodes should be prevented from unfavorable oxide and Passive layer formation on the machined surface or overall corrosion of the entire surface. Generally, metal electrodes corrode, passivate or dissolve in the electrochemical cell according to the electrode potential. Therefore, each electrode must maintain its stable potential. Tn this paper, the stable electrode potentials of tool and workpiece were determined using the potentiodynamic polarization test and verified experimentally considering machining stability and surface quality. Stable workpiece electrode potentials of two different passive materials of 304 stainless steel and nickel were determined in the 0.1 M sulfuric acid. Experimental results show good machined surface and fast machining rate using the determined electrode potentials.

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권8호
• /
• pp.828-832
• /
• 2015

This study is conducted for the evaluation of corrosion and lifetime prediction of fire extinguishing pipelines in residential buildings. The fire extinguishing pipeline is made of carbon steel. Twenty-four samples were selected among all the fire extinguishing pipelines in a building; the selection was based on specimenspositions, pipeline diameters, and pipeline thickness. Analysis was conducted by using the results of visual inspection, electrochemical potentiodynamic anodic polarization test, pitting depth measurements, and extreme value statistics with the Gumbel distribution. The maximum pitting depth and remaining life were statistically predicted using extreme value statistics. During visual inspection, pitting corrosion was observed in several samples. In addition, extreme value statistics demonstrated that there were several pipelines that were very sensitive to pitting corrosion. However, the pitting corrosion was not critical in all the pipelines; thus, it was necessary to change only those pipelines that were severely corroded.

• 대한화학회지
• /
• 제58권1호
• /
• pp.85-91
• /
• 2014

The corrosion behavior of aluminum and mild steel in hydrochloric acid medium was studied using a nicotinic acid hydrazide as inhibitor by potentiodynamic polarization, electrochemical impedance spectroscopy technique and gravimetric methods. The effects of inhibitor concentration and temperature were investigated. The experimental results suggested, nicotinic acid hydrazide is a good corrosion inhibitor for both aluminum and mild steel in hydrochloric acid medium and the inhibition efficiency increased with increase in the inhibitor concentration. The polarization studies revealed that nicotinic acid hydrazide exhibits mixed type of inhibition. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the aluminum and mild steel surface and inhibits corrosion by blocking the reaction sites on the surface of aluminum.

• Journal of Welding and Joining
• /
• 제15권5호
• /
• pp.124-133
• /
• 1997

Corrosion behavior of welded SWS400 steel used for bridges was studied in a range of the acid-rain environment using immersion, potentiodynamic polartization, polarization resistance, and galvanic corrosion tests. The SWS400 steel exhibited active corrosion behavior in the range of acid-rain environment, i.e. no passivation. As the results of immersion corrosion test, Tafel extrapolation method, and polarization resistance measurement, the average corrosion rats of the steels were 0.31-0.72 mm/year in the pH of 4-5, and 0.17 mm/yera in the pH 6, respectively. The steel showed a resistance to corrosion in the pH 6. The observed active behavior of SWS400 steel in chloride-containing environment indicated that the chloride ions exerts a detrimental influence on the formation of passive films. Galvanic corrosion was observed between the weld and the base metals because the weld is anodic to the base metal.

• 한국철도학회논문집
• /
• 제4권2호
• /
• pp.62-70
• /
• 2001

Pure copper, Cu-1.1wt%Cd and ACSR(Aluminum Conductor Steel Reinforced) have been used as catenary materials of the electric railway system. Since these materials may be exposed to the corrosive environments like polluted air, acid rain and sea water, it is important to investigate the corrosion rates in various corrosive environments. The aqueous corrosion characteristics of catenary materials in aerated acid, neutral and alkali solutions were studied by using immersion corrosion tests, electrochemical measurements and analytical techniques. In order to examine corrosion characteristics according to the dissolved oxygen content, pH, chloride ion concentration ion, and the addition of Cd to Cu, a series of tests such as potentiodynamic polarization, a.c impedance spectroscopy and galvanic corrosion tests were carried out with these materials. Results showed that the addition of Cd to Cu and chloride ion in the solution have an adverse effects on the resistance to corrosion. Additionally, Galvanic currents between Al and steel wires of ACSR were confirmed by using ZRA(zero resistance ammeter) method.

• 대한화학회지
• /
• 제57권6호
• /
• pp.672-676
• /
• 2013

The corrosion inhibition nature of Ginger affinale extract for the corrosion of mild steel in 0.5N $H_2SO_4$ was investigated using weight loss, electrochemical impedance and potentiodynamic polarization methods. The results revealed that Ginger affinale extract acts as a good corrosion inhibitor in 0.5N $H_2SO_4$ medium. The inhibition efficiency increased with an increase in inhibitor concentration. The inhibition could be attributed to the adsorption of the inhibitor on the steel surface.

• 한국표면공학회지
• /
• 제22권3호
• /
• pp.128-134
• /
• 1989

Mechanism of cobalt deposition was investigated using the potentiodynamic potentiostatic methods in solution of pH 4 and pH6.4 In all experimental conditions, polarization curves showed two regions with different Tafel slopes and the reaction order of cobalt ion was varied with the pH. It is belived that the deposition mechanism depends not only on the portential but also on the ph.

• Journal of Electrochemical Science and Technology
• /
• 제10권1호
• /
• pp.37-54
• /
• 2019

A new organic Schiff base compound N-benzylidene-2,5-dichloroaniline (BDC) was synthesized and the structure of the Schiff base is illuminated by some spectroscopic techniques. In addition, whether it is an applicable inhibitor in the industrial field was examined by conventional methods such as linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization for different concentrations. The BDC concentration and temperature effects were surveyed for elucidating the inhibitive mechanism. The BDC molecules are adsorbed to surface of mild steel via the Langmuir isotherm. Atomic force (AFM) and scanning electron microscope (SEM) techniques were utilized to give insight into surface characterization.

• 대한화학회지
• /
• 제55권3호
• /
• pp.495-501
• /
• 2011

플라보노이드계 화합물인 HMPC (3-hydroxy-7-methoxy-2-phenylchromen-4-one의 부식억제성질, HMPC와 TBAB(n-tetrabutylammonium bromide) 간 상승효과, 염산 조건하 부드러운 강철의 흡착성질을 무게 감량, 변전위 편극, 전기화학 임피던스 분광기를 사용하여 연구하였다. 다양한 온도에서 무게 감량 측정 실험한 결과 부식 억제 효율은 억제제 농도가 증가함에 따라 증가하였고, 계의 온도가 증가함에 따라 감소하였다. 전기화학 실험 결과 부식 억제는 여러 혼합된 형태의 억제 방법에 의해 가능하였다. 금속 표면에 흡착된 억제 화합물 분자는 보호막을 형성하였다.