• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.592-596
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• 2004

Corrosion is never avoided in the use of materials with various environments. The underwater hull is normally protected against rusting by several coatings of anti-corrosive paint. The purpose of ICCP(Impressed Current Cathodic protection) system is to eliminate the rusting or corrosion, which occurs on metal immersed in seawater. The anode of ICCP system is controlled by an external DC source with converter. The function of anode is to conduct the protective current into seawater. The proposed algorithm includes the harmonic suppression control strategy and the optimum protection strategy and has tried to test the requirement current density for protection, the influence of voltage, the protection potential. This paper was studied the variation of potential and current density with environment factors, time and velocity, and the experimental results will be explained.

• Journal of the Korean institute of surface engineering
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• v.31 no.3
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• pp.157-164
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• 1998

Effects of alloying elements on the pitting behavior of Ti-Al intermetalic compounds in the electrolytic soution containing Cl- were investigated through electrochemical tets and corrosion morphologies. Corrosion potential increased in the case of Cr addition to Ti-48%Al, whereas it decreased in the case of Si and B addition. The simultaneous addition of Cr and Si increased passive current density and decrosion corrosion potential. The passive current density of N addtion was higher than that of B addition in H2SO4 solution. With the addition of alloying elements, The pitting resistance decreased in order of TiAl>TiAlSi>TiAlN>TiAlB>TiAlCr and whin siumultaneous addition, it decreased in order of TiAlCrSi>TiAlCrBN>TiAlCrrN. The surface merohology after pitting test showed that the TiAl coataining Si had for fewer pits than that containing Cr and N simultaneously.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.393-400
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• 1999

The surface characteristics of nitrogen ion implanted iron aluminides were investigated using various electrochemical methods in $H_2$$SO_4$+KSCN and HCl solutions. Nitrogen ion implantation was performed with doses of $3.0$\times$10^{17}$ /ions/$\textrm{cm}^2$ at an energy of 150keV. Nitrogen ion implanted iron aluminides increased the corrosion potential and significantly decreased grain boundary activation, the active current density, and passive current density. Nitrogen implanted iron aluminides with Mo increased the corrosion, pitting potential, repassivation potential and │$E_{pit}$-$E_{corr}$│ value. Whereas, implanted iron aluminides containing boron reduced the pitting and repassivation potential in comparison with nitrogen implanted iron aluminides with Cr and Mo.o.

• Corrosion Science and Technology
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• v.8 no.1
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• pp.27-39
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• 2009

Non metallic composite materials, for example, GECM(graphite epoxy composite material) show high specific strength because of low density. These kinds of non metallic composite materials improved the structural effectiveness and operation economics. However, if these materials contacted several metals, corrosion can be arisen since non metallic composite materials have electrical conductivity. This paper dealt with galvanic corrosion between graphite epoxy composite material and several metals. Base on the electrochemical galvanic corrosion test between GECM and metals, corrosion current of carbon steel and aluminium increased with time but corrosion current of stainless steels and titanium decreased and galvanic potential increased. This behavior shows the galvanic corrosion depends upon the presence of passive film. Also, galvanic effect of GECM coupled with ferrous alloys and non-ferrous alloys was lower than that of 100% graphite, which is attributed to lower exposed area of graphite fiber in the GECM than apparent area of the GECM specimen used for the calculation of galvanic current in this work.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.171-176
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• 2004

Electro chemical corrosion tests were conducted on two structural steels, SS400 and SM490A, in various solutions with different pH values, All materials showed typical active corrosion behaviors in the solutions, and corrosion potential and current density were measured from the slopes obtained from the Tafel curves using linear polarization method. Corrosion potential increased in the acidic region and then decreased depending on the pH values of the solutions. All materials showed the fast corrosion rate in artificial acid rain(pH=4.7), but the slower corrosion rate was observed in NaOH solution(pH=12.0) for SS400 and in distilled water(pH=7.0) for SM490A, respectively, which is thought to come from the difference in chemical composition of two alloys. Generally homogeneous corrosion occurred in acid rain condition, and almost no corrosion was observed in distilled water in both alloys. NaOH solution produced more corrosion than distilled water, and more corrosion had progressed in SS400 than in SM490A in $3.5\%$ NaCl solution.

• Corrosion Science and Technology
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• v.7 no.3
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• pp.168-172
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• 2008

A new type of electrochemical random signal (electrochemical noise) analysis technique was applied to localized corrosion of anodic oxide film formed 1100 aluminum alloy in $0.5kmol/m^3$ $H_3BO_4/0.05kmol/m^3$ $Na_2B_4O_7$ with $0.01kmol/m^3$ NaCl. The effect of anodic oxide film structure, barrier type, porous type, and composite type on galvanic corrosion resistance was also examined. Before localized corrosion started, incubation period for pitting corrosion, both current and potential slightly change as initial value with time. The incubation period of porous type anodic oxide specimens are longer than that of barrier type anodic oxide specimens. While pitting corrosion, the current and potential were changed with fluctuations and the potential and the current fluctuations show a good correlation. The records of the current and potential were processed by calculating the power spectrum density (PSD) by the Fast Fourier Transform (FFT) method. The potential and current PSD decrease with increasing frequency, and the slopes are steeper than or equal to minus one (-1). This technique allows observation of electrochemical impedance changes during localized corrosion.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.30-36
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• 2018

The high rate of corrosion of magnesium alloys makes it limited for industrial applications. Therefore, surface treatment is required to enhance their corrosion resistance. In our study, a chemical conversion coating for protecting the corrosion of the magnesium alloy, AZ31B, was prepared by using a phosphate-permanganate solution. The chemical conversion coating had a limited protection ability due to defects arising from cracks and pores in the coating layer. The sol-gel coating was prepared by using trimethoxymethylsilane (MTMS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) as precursors, and aluminum acetyl acetonate as a ring opening agent. The corrosion protection properties of sol-gel and conversion coatings in 0.35wt% NaCl solution were measured by the electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization test. The EIS results indicated that the resistance of the chemical conversion coating with the sol-gel coating was significantly improved through the sol-gel sealed phosphate-permanganate conversion coating. The results of the potentiodynamic polarization test revealed that the sol-gel coating decreased the corrosion current density ($I_{corr}$). The SEM image showed that the sol-gel coating sealed conversion coating and improved corrosion protection.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.294-299
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• 2010

Two types of welding methods were performed on austenitic 304 stainless steel: laser welding and TIG welding. The differences of the corrosion characteristics of the welded zones from the two welding methods were investigated with electrochemical methods, such as measurement of the corrosion potential, polarization curves, cyclic voltammogram, etc. The vickers hardness of all laser-welded zones (WM:Weld Metal, HAZ:Heat Affected Zone, BM:Base Metal) was relatively higher while their corrosion current densities exhibited a comparatively lower value than those which were TIG welded. In particular, the corrosion current density of the TIG-welded HAZ had the highest value among all other welding zones, which suggests that chromium depletion due to the formation of chromium carbide occurs in the HAZ, which is in the sensitization temperature range, thus it can easily be corroded with an active anode. Intergrenular corrosion was also observed at the TIG-welded HAZ and WM zones. Consequently, we can see that corrosion resistance of all austenitic 304 stainless steel welding zones can be improved via the use of laser welding.

• 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.

• Journal of Fisheries and Marine Sciences Education
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• v.19 no.1
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• pp.84-90
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• 2007

This paper was studied on the electrochemical corrosion characteristics of weld zone for refrigerating and heating systems pipe. Austenitic stainless steel is widely applied to various fields of industry, because it is good to corrosion resistance and mechanical properties. But STS 304 is reliable to sensitization by heat cycle on welding. Therefore, in this study, electrochemical polarization test of STS 304 steel pipe manufactured by arc welding in tap water was carried out. And then polarization resistance behavior, uniform and local corrosion behaviors of base metal(BM), weld metal(WM) and heat affected zone(HAZ) for STS 304 pipe were investigated. The corrosion current density of STS 304 steel pipe is high in order of BM(153nA/cm2) < WM(614nA/cm2) < HAZ ($1.675{\mu}A/cm2$). The pitting potential of HAZ(238mV/SCE) for STS 304 is lower than BM(1206mV/SCE) and WM(369mV/SCE). Therefore, the local corrosion like pitting corrosion, galvanic corrosion and crevice corrosion of HAZ for STS 304 is more sensitive than BM and WM.