• Corrosion Science and Technology
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• 제19권5호
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• pp.259-264
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• 2020

Many studies have been conducted to improve the corrosion resistance and durability of various aluminum alloys through the anodizing technique. It is already used as a unique technique for enhancing the properties of aluminum alloys in various industries. This paper investigated the electrochemical corrosion and stress corrosion cracking characteristics of anodized aluminum 5083-H321 alloy in natural seawater. The corrosion characteristics were assessed by the electrochemical technique and potentiodynamic polarization test. The stress corrosion cracking characteristic was evaluated with a slow strain rate tensile test under 0.005 mm/min rate, which showed that the hard anodizing film had a thickness of about 16.8 ㎛. Although no significant characteristics of stress corrosion cracking were observed in the slow strain rate test, the anodized specimen presented excellent corrosion resistance. The corrosion current density was measured to be approximately 4.2 times lower than that of the base material, and no surface damage was observed in the anodic polarization test.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.97-118
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• 2019

Based on Nonlinear Finite Element Analysis (NFEA), this paper focuses on the bi-axial ultimate strength of typical bottom structures under corrosion. On one hand, uniform and not simultaneous corrosion across different structures is introduced, and surrogate models by Gaussian Process (GP) are built for both longitudinal and transverse cases individually, and corresponding probabilistic characteristics are investigated; meanwhile, corrosion effects on interaction between bi-axial stresses at ultimate state are studied. On the other hand, non-uniform localized pitting corrosion of normally distributed circular shapes is introduced, and different pitting corrosion densities are considered; structural bi-axial ultimate strengths under pitting corrosion are studied, and the results are compared with that from equivalent uniform corrosion; the probabilistic characteristics of structural ultimate strength in life cycle are studied; finally, the ultimate strength under randomly distributed pitting corrosion is compared with results from normally distributed pitting and uniform corrosion under various boundary conditions.

• 동력기계공학회지
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• 제18권6호
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• pp.40-44
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• 2014

The purpose of this paper is to investigate polarization characteristics of WC-based alloy coatings in alkaline solution. The coatings were fabricated with WC-CrC-Ni, WC-Co-Cr and WC-Co composite powders by HVOF process. Corrosion tests of coatings and substrate were carried out using potentiostat/galvanostat at solution with pH 8 and pH 13. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be studied from polarization curve, and corrosion behavior was analyzed by SEM and EDS. WC-Co-Cr coating and WC-CrC-Ni coating showed more favorable anti-corrosion characteristics than WC-Co coating and substrate at solution with pH 8 and pH 13.

• Tribology and Lubricants
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• 제16권3호
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• pp.173-181
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• 2000

Friction, wear and corrosion characteristics of various MoS$_2$ bonded film lubricants were investigated to apply them to automotive wheel joints. MoS$_2$ bonded film lubricants were formulated by combinations of several additives and binders, and they were coated onto the pre-treated surfaces of specimens. Friction and wear characteristics were evaluated with Falex pin & vee-block test and LFW-1 block-on-ring test. For the corrosion resistant characteristics of the films, salt solution spray corrosion tests were performed. Results showed that MoS$_2$ bonded films containing both inorganic and organic corrosion-resistant additives yielded a synergy effect on anti-corrosion resistance. Also, binders having the better water-proof and thermal stability showed the lower friction and higher corrosion resistance.

• 동력기계공학회지
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• 제18권4호
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• pp.72-77
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• 2014

The aim of this study to investigate polarization characteristics of WC-based alloy coatings fabricated by high velocity oxygen fuel(HVOF) process. The coatings were fabricated by HVOF process with WC-CrC-Ni, WC-Co-Cr, WC-Co composite powders. Corrosion tests were carried out using potentiostat/galvanostat at solution with pH 2 and pH 6. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be analyzed from polarization curve. WC-Co-Cr coating showed more incorrodible characteristics than other coatings at solution pH 2. WC-CrC-Ni coating was more favorable anti-corrosion characteristics than other coatings at solution with pH 6.

• Corrosion Science and Technology
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• 제20권2호
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• 동력기계공학회지
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• 제17권4호
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• pp.79-85
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• 2013

This study aims at investigating the effect of a fusing treatments on anti-corrosion characteristics of Ni-based self-flux alloy coating. Ni-based coatings were fabricated by flame spray process on steel substrates, and fusing treatments were performed using a vacuum furnace at $800^{\circ}C$ $900^{\circ}C$, $1000^{\circ}C$ and $1100^{\circ}C$. After fusing treatments, corrosion tests were carried out using potentiostat/galvanostat at solution with pH 2 and pH 6. Corrosion potential(Ecorr) and corrosion current density(Icorr) could be analyzed from polarization curve. Fusing-treated coating at $1100^{\circ}C$ showed more favorable anti-corrosion characteristics than as-sprayed coating. Anticorrosive effect of fusing-treated coating at solution with pH 2 was relatively greater than at solution with pH 6. Fusing-treated coating at $1100^{\circ}C$ showed the most excellent anti-corrosion characteristics.

• 헤리티지:역사와 과학
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• 제53권1호
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• pp.24-33
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• 2020

출토 청동 유물에서는 매장 환경 내 공존하는 복합적인 부식 인자로 인해 다양한 형태와 색상의 부식 생성물이 관찰되며, 이러한 부식 생성물은 장기 부식의 정보뿐만 아니라 보존처리 시 중요한 자료가 될 수 있다. 따라서 청동 유물의 부식층 및 부식 생성물에 대한 과학적 분석을 실시하여 부식층 형성 과정 및 부식 생성물의 특성을 규명하고, 노출된 매장 환경의 특성 및 내부 부식 인자와의 연관성을 해석하는 연구가 필수적이다. 본 연구에서는 동일 유적에서 출토된 청동 유물을 합금비와 제작기법에 따라 분류 후, 표면·부식층·부식 생성물에 대한 종합적인 분석을 실시하여 청동 유물의 부식 메커니즘과 부식층 형성 과정, 부식 생성물의 특성에 대해 알아보고자 하였다. 분석 대상으로 선정된 총 5점의 시료는 합금비 및 제작기법 분석 결과에 따라 2개의 그룹으로 구분되는데, Cu-Sn-Pb합금으로 열처리가 진행되지 않은 Group 1은 내·외측 중 일부 또는 양측에 외부 부식층이 형성되어 있으며, 표면은 녹색 또는 청색으로 확인되었다. 소지 금속에서는 α상, α+δ상 선택 부식이 일어나는 것을 알 수 있었으며, α+δ상 선택 부식 후 빈 공간에 순도가 98% 이상인 Cu가 농축되어 있는 현상이 확인되었다. Cu-Sn합금으로 열처리가 진행된 Group 2는 외부 부식층이 형성되지 않았으며, 표면이 어두운 황색으로 관찰되었다. 또한 Group 1과는 다르게 소지 금속 내부에서 α상 선택 부식이 발생한 것을 확인하였다. 연구결과를 종합해 볼 때 동일한 유적에서 출토된 청동 유물에서도 합금비 및 제작기법에 따라 부식층 형성과정 및 부식 생성물의 형태와 색상, 금속이온 이동경로 등 여러 측면에서 차이를 나타냄을 알 수 있다. 또한 동일 유물에서도 부분적으로 서로 다른 부식 특성을 보이기도 하는데 이는 매장 환경 내 노출 환경에 따라 다른 형태의 부식이 발생할 수 있음을 뜻한다. 따라서 동일 유적에서 출토된 청동 유물이라 하더라도 합금비, 제작기법, 노출 환경에 따라 부식 특성이 다를 것이라고 판단된다. 본 연구는 특정 지역 및 유물을 대상으로 한 부식 특성의 일면을 보여주는 것이므로 향후 여러 지역에서 출토되는 청동 유물의 부식층 및 부식 생성물 특성에 대한 연구를 통해 매장 환경에 따른 부식 메커니즘에 대한 심층적인 연구가 필요할 것으로 판단된다.

• 상하수도학회지
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• 제21권6호
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• pp.689-699
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• 2007

The accurate estimation of water pipe deterioration is indispensable to prevent pipe breakage and manage in advance. In this study, corrosion of water pipe is adopted, which is relatively underestimated although it takes most part of deteriorating pipeline. Predicting corrosion rate and corrosion depth of a pipe can make an increase the life span of the pipeline, which is laid under the ground according to characteristics of soil and water corrosion. For the purpose, mathematical models that can presume nominal depth through estimation of pit corrosion and corrosion rate is introduced. As comparison of results with conventional methods in other foreign countries, it is evaluated that the external corrosion depth is estimated less than the models, proposed by other researchers and the internal corrosion rate was processed faster than the external corrosion rate.

• Tribology and Lubricants
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• 제35권2호
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• pp.139-147
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• 2019

This study investigates the effects of corrosion resistance characteristics of opponent materials in relative motion on the sliding wear behavior of mild carbon steel. Pin specimens made of mild carbon steel are tested at several sliding speeds against mating discs made of two types of alloyed steels, such as type D2 tool steel (STD11) and type 420 stainless steel (STS420J2), with different corrosion resistance characteristics in a pin-on-disc type sliding wear test machine. The results clearly show that the sliding wear behavior of mild carbon steel is influenced by the corrosion resistance characteristics of the mating disc materials at low sliding speeds. However, the sliding wear behavior at high sliding speeds is irrelevant to the characteristics because of the rising temperature. During the steady state wear period, the sliding wear rate of mild carbon steel against the type 420 stainless steel at a sliding speed of 0.5 m/s increases considerably unlike against the type D2 tool steel. This may be because the better corrosion resistance characteristics achieve a worse tribochemical reactivity. However, during the running-in wear period at low sliding speeds, the wear behavior of mild carbon steel is influenced by the microstructure after heat treatment of the mating disc materials rather than by their corrosion resistance characteristics.