• Corrosion Science and Technology
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• v.22 no.2
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• pp.108-114
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• 2023

In this study, anti-corrosion effect was investigated through various electrochemical experiments after applying Al thermal spraying technology to AA5083-H321. Open circuit potential and anodic polarization curves were analyzed through electrochemical experiments in natural seawater. The shape of the surface was observed using a scanning electron microscope (SEM) and a 3D microscope before and after the experiment. Component and crystal structure were analyzed through EDS and XRD. As a result, the surface roughness of AA5083-H321 and the Al thermal sprayed coating layer increased due to surface damage caused by anodic dissolution reaction during the anodic polarization experiment. The corrosion rate of AA5083-H321 was relatively low because the Al thermal spray coating layer contained structural defects such as pores and crevices. Nevertheless, the open circuit potential of the Al thermal spray coating layer in natural seawater was measured about 0.2 V lower than that of AA5083-H321. Thus, a sacrificial anode protection effect can be expected.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.10a
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• pp.208-208
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• 2009

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.282-282
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• 2012

• Corrosion Science and Technology
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• v.19 no.5
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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.

• Journal of the Korean institute of surface engineering
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• v.52 no.1
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• pp.23-29
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• 2019

Electrolytic corrosion of the ship's hull can be occurred due to stray current during welding work using shore power and electrical leakage using shore power supply. The electrolytic corrosion characteristics were investigated for Al5083-H321 through potentiodynamic polarization and galvanostatic corrosion test in natural seawater. Experiments of electrolytic corrosion were tested at various current densities ranging from $0.01mA/cm^2$ to $10mA/cm^2$ for 30 minutes, and at various applied time ranging from 60 to 240 minutes. Evaluation of electrolytic corrosion was carried out by Tafel extrapolation, weight loss, surface analysis after the experiment. In the electrolytic corrosion characteristics of Al5083-H321 as the current density increased, the surface damage tended to proportionally increase. In the current density of $0.01mA/cm^2$ for a applied long time, the damage tended to grow on the surface. In the case of $10mA/cm^2$ current density for a applied long time, the damage progressed to the depth direction of the surface, and the amount of weight loss per hour increased to 4 mg/hr.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.310-317
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• 2020

This study investigated the damage to the specimen due to liquid droplet impingement erosion corrosion, which improved the corrosion resistance and durability via hard anodization of 5083-H321 aluminum alloy, which is widely used for small ships and marine structures. The experiment combined liquid droplet impingement erosion and electrochemical equipment with the flow rates in natural seawater solution. Subsequently, Tafel extrapolation of polarization curves was performed to evaluate damage due to the liquid droplet impingement erosion corrosion. The damaged surface was observed using a 3D microscope and a scanning electron microscope. The degree of pitting damage was measured using the Image J program, and the surface hardness was measured using the micro-Vickers hardness tester. The corrosion current density, area, depth, and ratio of the damaged areas increased with the increase in flow rate. The grain size of the damaged area at a flow rate of 20 m s-1 showed fewer and minor differences in height, and a smooth curved shape. The hardness of the damaged surface tended to decrease with increase in flow rate.

• Corrosion Science and Technology
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• v.19 no.6
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• pp.288-295
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• 2020

This study investigated the erosion-corrosion characteristics of 5038-H321 aluminum alloy in a natural seawater solution through various electrochemical experiments and flow rate parameters. Cathodic polarization experiments were conducted at flow rates ranging from 4 to 12 knots. Considering the concentration polarization section representing a relatively low current density, the range of the potentiostatic experiment was determined to be -1.6 to -1.0 V. The potentiostatic experiment was conducted at various potentials for 180 minutes in seawater. After the experiment, the corrosion characteristics were evaluated by observing surface morphology and measuring surface roughness. As a result, as the applied potential was lower, the amount of calcareous deposits increased and the roughness tended to increase. On the other hand, it was confirmed that the roughness was larger in the static condition than the flow rate condition due to the influence of the flow velocity. Variations in the chemical composition with flow rate variations were analyzed by energy-dispersive spectroscopy (EDS). In conclusion, the cathodic potential of AA5083-H321 in seawater was determined to be -1.0 V.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.143-143
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• 2016

알루미늄 합금은 내구성과 내식성이 우수할 뿐만 아니라 다양한 표면개질을 통해 그 표면 특성을 더욱 향상시킬 수 있다. 특히 Al-Mg계 5083-H321 Al 합금의 경우 가공성 및 용접성이 우수하여 선체 재료로 널리 이용되는데, 이는 선체중량의 경량화가 가능하여 연료비 절감과 빠른 선속 등 다양한 이점을 지니기 때문이다. 그러나 선속의 고속화에 따라 선체에 가해지는 유체충격이 증가하고 정압 저하에 기인하여 캐비테이션-침식 손상이 증가할 뿐만 아니라 해수환경 특성 상염소이온의 존재로 부식이 가속화되는 등 침식 및 부식의 시너지효과로 손상은 크게 증가한다. 이에 대한 방지대책으로 다양한 표면개질 기법이 제안되고 있으나 강한 충격압이 동반된 캐비테이션 침식-부식 복합 손상 환경에서는 표면처리만으로는 불가능할 수 있다. 따라서 본 연구에서는 양극산화된 5083-H321을 대상으로 캐비테이션 환경 하에서 일정 전위를 인가하여 침식-부식 손상이 최소화되는 최적전위를 규명하고자 한다. 이를 위해 먼저 분극 실험을 통해 재료의 전기화학적 거동을 바탕으로 임의의 전위를 선정하고 해당 전위를 인가한 상태에서 캐비테이션 실험을 실시하였다. 이때 분극실험과 캐비테이션-전기화학 복합실험 모두 $25^{\circ}C$의 해수에서 실시하였으며, 전기화학적 분극실험은 유효면적이 $3.24cm^2$인 시편에 2 mV/s의 분극속도로 0 ~ -3 V 까지 인가하였고, Ag/AgCl 기준전극과 백금대극을 사용하였다. 캐비테이션-전기화학 복합 실험은 정전위를 인가한 상태에서 $30{\mu}m$의 진폭으로 20분간 실시하였으며, 혼팁과 시험편 사이의 거리는 1 mm로 일정하게 유지하였다. 실험 후 표면 손상의 정량적 분석을 위해 인가된 전위별 전류밀도를 비교하고, 무게감소량을 측정하였으며, 손상특성 분석을 위해 3D현미경과 주사전자현미경(SEM)을 통해 표면을 분석하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2017.05a
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• pp.137-137
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• 2017

Al-Mg 합금은 비중이 적고 강도가 우수하기 때문에 해양 환경에서 구조용 재료로 많이 사용되고 있으며, 특히 선박용 재료로 사용될 경우 선체의 중량을 줄일 수 있어 연료비가 절감되며 선속의 고속화가 가능하다. 그러나 해양환경에서의 재료 특성에 관한 지식 및 관련 기술 부족으로 알루미늄 선박 건조는 활성화 되지 못하고 있는 실정이다. 알루미늄 합금은 공기 중에서는 우수한 내식성을 지니는 것으로 알려져 있으나 해수환경에서는 염소이온에 의한 부동태 피막 파괴로 인해 내식성이 저하되며 공식 및 응력부식균열 등에 의한 손상이 발생할 수 있다. 특히 용접부의 경우, 모재에 비해 부식손상에 취약하며 기공과 같은 용접 결함을 포함하고 있어 구조물 파괴의 시발점이 될 수 있으므로 선박 및 구조물 건조시 대비가 필요하다. 그러나 이에 관한 충분한 연구가 이루어지지 않아 국내 중소형 조선소의 경우 알루미늄 선박 건조에 어려움을 겪는 경우가 많다. 따라서 본 연구에서는 선박 건조 및 해양 구조물에 널리 사용되는 Al 5083-H321 합금 용접부에 대하여 해수 내 부식 특성을 연구하고자 한다. 부식특성 파악을 위한 전기화학적 실험에 앞서 화학적 에칭을 통해 미세부위별 실험을 수행하였다. 기준전극은 은/염화은 전극을 대극은 백금전극을 사용하였으며, 타펠 분석을 위한 분극실험은 OCP를 기준으로 -0.25 ~ +0.25 V까지 실시하였고 양극분극실험은 OCP ~ +3.0 V까지 실시하였다. 양극분극 실험 후 부식된 표면은 주사전자현미경과 3D 분석을 통해 용접부 조직에 따른 전기화학적 특성을 관찰하였다.

• Corrosion Science and Technology
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• v.19 no.3
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• pp.115-121
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• 2020

In this study, erosion tests and erosion-corrosion tests of Al5083-H321 aluminum alloy were conducted at various flow rates in seawater. The erosion tests were conducted at a flow rate of 0 to 20 m/s, and erosion-corrosion tests were performed by potentiodynamic polarization method at the same flow rate. Characteristic evaluation after the erosion test was conducted by surface analysis. Characteristic evaluation after the erosion-corrosion test was performed by Tafel extrapolation and surface analysis. The results of the surface analysis after the erosion test showed that surface damage tended to increase as the flow rate increased. In particular, intermetallic particles were separated due to the breakdown of the oxide film at 10 m/s or more. In the erosion-corrosion test, the corrosion current density increased as the flow rate increased. Additionally, the surface analysis showed that surface damage occurred in a vortex shape and the width of the surface damage tended to increase as the flow rate increased. Moreover, damage at 0 m/s, proceeded in a depth direction due to the growth of pitting corrosion, and the damaged area tended to increase due to acceleration of the intermetallic particle loss by the fluid impact.