• Corrosion Science and Technology
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• v.20 no.2
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.85-90
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• 1993

This study was performed for the purpose of obtaining the fundamental data to establish the criterion of concrete deterioration and presuming steel corrosion of concrete structures under the environment of seawater. It was exposed in seawater for 1 year that steel was embedded in the concrete specimen. The diffusion coefficients of concrete, corrosion potential and steel corrosion were considered. The results show that corrosion potential is reduced according to steel corrosion and corrosion area ratio is correlative with diffusion coefficients of concrete.

• Journal of the Korean institute of surface engineering
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• v.36 no.4
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• pp.324-328
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• 2003

This study was made on the crevice corrosion behavior of chromium plating in fresh water. Under the various crevice, the electrochemical polarization test of chromium plating was carried out. Results are discussed In terms of corrosion potential, polarization resistance, corrosion current density and cathodic control of chromium plating.

• Journal of the Korean institute of surface engineering
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• v.39 no.1
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• pp.25-34
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• 2006

Al-Mg alloy, an open rack vaporizer(ORV) material was reported to be corroded in seawater environments though the ORV material was coupled to thermally sprayed Al-Zn alloy functioning a sacrificial anode. In addition, the corrosion behavior based on the calculated corrosion potential did not match the observed corrosion behavior. Hence, the goal of this study is to get better understanding on Al or Al-Mg alloy coupled to Al-Zn alloy and to provide the calculated corrosion potential representing the corrosion behavior of the ORV material by immersion test, electrochemical tests, and calculation of corrosion and galvanic potential. The corrosion potentials of Al and Al alloys also depended on alloying element as well as surface defects. The corrosion potentials of Al and Al-Mg alloy were changed with time. In the meantime, the corrosion potentials of Al-Zn alloys were not. The corrosion rates of Al-Zn alloys were exponentially increased with zinc contents. The phenomena were explained with the stability of passive film proved by passive current density depending on pH and confirmed by the model proposed by McCafferty. Dissimilar material crevice corrosion (DMCC) test shows that higher content of zinc caused Al-Mg alloy corroded more rapidly, which was due to the fact that higher corrosion rate of Al-Zn makes [$H^+$] and [$Cl^-$] more concentrated within pit solution to corrode Al-Mg alloy. Considering electrochemical reactions within pit as well as bulk in the calculation gives better prediction on the corrosion behavior of Al and Al-Mg alloy as well as the capability of Al-Zn alloy for corrosion protection.

• Corrosion Science and Technology
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• v.7 no.2
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• pp.134-137
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• 2008

Cold arc welding of cast iron has been widely used with repair welding of metal structures. However its welding is often resulted in the galvanic corrosion between weld metal zone and heat affected zone(HAZ) due to increasing of hardness. In this study, corrosion properties such as hardness, corrosion potential, surface microstructures, and variation of corrosion current density of welding zone with parameters of used electrodes for cast iron welding were investigated with an electrochemical evaluation. Hardness of HAZ showed the highest value compared to other welding zone regardless of kinds of used electrodes for cast iron welding. And its corrosion potential was also shifted to more negative direction than other welding zone. In addition, corrosion current density of WM in polarization curves was qualitatively smaller than that of HAZ. Therefore galvanic corrosion may be apparently observed at HAZ. However galvanic corrosion may be somewhat controlled by using an optimum welding electrode.

• Corrosion Science and Technology
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• v.20 no.1
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• pp.37-43
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• 2021

Additively manufactured (AM) Ti-6Al-4V alloys exhibit a dominant acicular martensite phase (α'), which is characterized by an unstable energy state and highly localized corrosion susceptibility. Electrochemical critical localized corrosion temperature (E-CLCT, ISO 22910: 2020) and electrochemical critical localized corrosion potential (E-CLCP, ISO AWI 4631: 2021) were measured to analyze the localized corrosion resistance of the AM Ti-6Al-4V alloy. Although E-CLCP was measured under mild corrosive conditions such as human body, the validity of evaluating localized corrosion resistance of AM titanium alloys was demonstrated by comparison with E-CLCT. However, the mechanisms of resistance to localized corrosion on the as-received and heat-treated AM Ti-6Al-4V alloys under E-CLCT and E-CLCP differ at various temperatures because of differences in properties under localized corrosion and repassivation. The E-CLCT is mainly measured for initiation of localized corrosion on the AM titanium alloys based on temperature, whereas the E-CLCP yields repassivation potential of re-generated passive films of AM titanium alloys after breaking down.

• Journal of the Korean institute of surface engineering
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• v.37 no.2
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• pp.110-118
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• 2004

The corrosion of pure titanium (CP- Ti Grade 2) and titanium alloy (Ti6Al4V ELI) were studied under various conditions of simulated body fluids. The static immersion test and the electrochemical test were performed in accordance with ISO 10271 : 2001. For the electrochemical test, the open circuit potential was monitored as a function of time, and the cyclic polarization curve was recorded. The corrosion resistance was evaluated from the values of corrosion potential, passivation current density, breakdown potential, and the shape of hysteresis etc. The effects of alloy type, surface condition, temperature, oxygen, and constituents in the fluids such as acid, chloride were estimated. Both specimens had extremely low dissolution rate in the static immersion test. They showed strong passivation characteristics in the electrochemical test. They maintained negligible current density throughout the wide anodic potential range. The passive layer was not broken up to 2.0 V (vs. SCE). The hysteresis and the shift of passivation potential toward the anodic direction was observed during the reversed scan. The passivation process appeared to be accelerated by oxygen in air or that dissolved in the fluids. The passivation also proceeded without oxygen by the reaction of constituents in the fluids. Acid or chloride in the fluids, specially later weakened the passive layer, and then induced higher passivation current density and less shift of passivation potential in the reversed scan. CP-Ti Grade 2 was more reactive than Ti6Al4V ELI in the fluids containing acid or chloride, but thicker layer produced on its surface provided higher corrosion resistance.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.3
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• pp.387-394
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• 2009

It has been observed that coated steel structures are rapidly deteriorated than designed lifetime due to acid rain caused by air pollution etc.. Therefore improvement of corrosion resistance of anti-corrosive paint is very important in terms of safety and economic point of view. In this study corrosion resistance for five kinds of anti-corrosive paints including acryl, fluorine and epoxy resin series were investigated with electrochemical methods such as corrosion potential, polarization curves, impedance and cyclic voltammogram measurements etc.. There were somewhat good relationships between values measured by electrochemical methods such as corrosion current density obtained by cathodic and anodic polarization curves, value of impedance estimated with AC impedance, and polarization resistance on the cyclic voltammogram, for example, corrosion current density was decreased with increasing of values of impedance and polarization resistance on the cyclic voltammogram. However their relationships between corrosion current density and corrosion potential were not well coincided each other. Consequently it is considered that although a corrosion potential of F101 of fuoric resin series shifted to negative direction than other anti-corrosive paints, its corrosion resistance, indicating on the cathodic and anodic polarization curves, AC impedance curves and cyclic voltammogram, was the most superior to other paints, whereas A100 containing arcylic resin showed a relatively poor corrosion resistance compared to other paints.

• Corrosion Science and Technology
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• v.18 no.3
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• pp.92-101
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• 2019

This study investigates how rivet head height affects the corrosion performance of carbon fiber reinforced plastic (CFRP) to aluminum alloy self-piercing riveted joints. Specimens with two different head heights were prepared. A rivet head protruding out of the top CFRP laminate forms the proud head height while a rivet head penetrating into the top CFRP generates the flush head height. The salt spray test evaluated corrosion performance. The flush head joints suffered from severe corrosion on the rivet head. Thus, the tensile shear load of flush head joints was substantially reduced. Electrochemical corrosion tests investigated the corrosion mechanisms. The deeper indentation of the flush head height damaged the CFRP around the rivet head. The exposure of damaged fibers from the matrix increased the cathodic potential of local CFRP. The increased potential of damaged CFRP accelerated the galvanic corrosion of the rivet head. After the rivet head coating material corroded, a strong galvanic couple was formed between the rivet head base metal (boron steel) and the damaged CFRP, further accelerating the flush rivet head corrosion. The results of this study suggest that rivet head flushness should be avoided to enhance the corrosion performance of CFRP to aluminum alloy self-piercing riveted joints.

• Computers and Concrete
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• v.33 no.6
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• pp.631-642
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• 2024

The present study concerns the corrosion mitigation of electrochemical chloride extraction (ECE) in concrete structure. Concrete specimen was fabricated with 5.0% chloride in cast, while the other specimen was exposed to 4.0M NaCl solution for 1 year to accelerate corrosion of steel. Then, the ECE was applied to the concrete specimen with 1000 mA/m² of the current density for 2, 4 and 8 weeks, respectively. During the ECE, the corrosion current density and corrosion potential were regularly monitored. As a result, the ECE was very effective in mitigating the degree of corrosion on the steel surface. The corrosion current density was significantly reduced from thousands to decades mA/m², while the corrosion potential was mostly shifted to positive direction. Assuming that the corrosion starts at 1.0 mA/m² of the corrosion current density or/and -275 mV vs SCE of the corrosion potential, the ECE could not fully achieve the repassivation of the steel, although its degree was lowered more or less depending on the duration of the treatment and type of chloride contamination. A visual examination confirmed that an increase in the duration of the treatment could lower the rust formation, but never fully removed all rust stains.