• Corrosion Science and Technology
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• 제16권3호
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• pp.151-159
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• 2017

The MA8 alloy (formula Mg-Mn-Се) has been shown to have greater corrosion stability than the VMD10 magnesium alloy (formula Mg-Zn-Zr-Y) in chloride-containing solutions by Scanning Vibrating Electrode Technique (SVET) and by optical microscopy, gravimetry, and volumetry. It has been established that the crucial factor for the corrosion activity of these samples is the occurrence of microgalvanic coupling at the sample surface. The peculiarities of the kinetics and mechanism of the corrosion in the local heterogeneous regions of the magnesium alloy surface were investigated by localized electrochemical techniques. The stages of the corrosion process in artificial defects in the coating obtained by plasma electrolytic oxidation (PEO) at the surface of the MA8 magnesium alloy were also studied. The analysis of the experimental data enabled us to determine that the corrosion process in the defect zone develops predominantly at the magnesium/coating interface. Based on the measurements of the corrosion rate of the samples with PEO and composite polymer-containing coatings, the best anticorrosion properties were displayed by the composite polymer-containing coatings.

• Corrosion Science and Technology
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• 제11권5호
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• pp.165-172
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• 2012

The corrosion resistance of epoxy-coated carbon steel was evaluated. The carbon steel surface was subjected to different treatment methods such as steel grit blasting with different size, steel shot ball blasting and power tool treatment. To study the effect of the treatments, the topology of the treated surface was observed by optical 3D microscopy and a pull-off adhesion test was conducted. The corrosion resistance of the epoxy-coated carbon steel was further examined by electrochemical impedance spectroscopy (EIS) combined with hygrothermal cyclic testing. The results of EIS indicated that the epoxy-coated carbon steel treated with steel grit blasting showed an improved corrosion resistance compared to untreated epoxy-coated surfaces or surfaces subjected to shot ball blasting and power tool treatments.

• 한국표면공학회지
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• 제36권3호
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• pp.272-283
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• 2003

Mild steel and zinc specimens were tested in five atmospheric testing sites of Vietnam in order to collect the corrosion databank as well as to study the corrosion mechanism in tropical conditions, in period of 1997-2000. The results obtained showed that the corrosion rate of steel is in the range of $10-50\;{\mu}m/year$ and of zinc is of $1-5\;{\mu}m/year$. They are interpretable in the comparison with the data obtained in different countries in the South East Asian as well as previous reports of Vietnamese nation project In atmospheric corrosion. The main factors affecting the corrosion in Vietnam tropical conditions are TOW (time of wetness) and salinity. The relationship between sulfur dioxide and corrosion of metals, particularly, zinc was not found clearly. An explanation was suggested about the complex effect of different pieces present in tropical atmosphere and about the alternative of the dominant factors such as humidity, salinity or temperature.

• 한국표면공학회지
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• 제53권5호
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• pp.207-212
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• 2020

Silver is an inexpensive precious metal and is used in various jewelry in Asia. Although silver has high potential, it has corrosion resistance that is vulnerable to boiling sulfuric acid and nitric acid. So, silver research is needed to prevent the corrosion with environment. But silver corrosion is not studied. sulfuric acid make the uniform corrosion and chloride ion make the pitting corrosion. ICCP inhibits the corrosion because it offset electrons. This study used a potential from - 4 V to 4 V to check the effect of potential. Corrosion rate is lowet at -1 V.

• 한국표면공학회지
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• 제45권5호
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• pp.198-205
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• 2012

The corrosion properties of anodized films on aluminium 6070 alloy in a sulfuric acid have been studied. Comparison to evaluate the anodized A6070 and pure 6070 specimen, corrosion tests in $HNO_3$ vapor environment of the 20 wt.% were performed up to 72 hours. Characteristics of film formation and surface morphology were examined by optical microscopy, FE-SEM, and EDS. The oxide film anodized in the sulfuric acid solution contained 5 to 10 wt.% of sulfur. In the initial stages of corrosion, anodized specimens exhibited corrosion resistance than the pure specimen. However, the corrosion conditions in 24 hours, corrosion was far more anodized specimen than pure specimen. Therefore, anodized films contained sulfur, nitric acid vapor in the environment is thought to stimulate corrosion.

• Corrosion Science and Technology
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• 제16권3호
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• pp.109-114
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• 2017

Monitoring of corrosion is in most cases based on simulation of environmental conditions on a large and complex structure such as a buried pipeline using a small probe, and the measurement of thermodynamics and kinetics of corrosion processes occurring on the probe surface. This paper presents a hybrid corrosion monitoring probe designed for simulating deteriorating conditions wrought by disbonded coatings and for measuring current densities and distribution of such densities on a simulated pipeline surface. The concept of the probe was experimentally evaluated using immersion tests under cathodic protection (CP) in high resistivity aqueous solution. Underneath the disbonded area, anodic currents and cathodic currents were carefully measured. Anodic current densities were used to calculate metal loss according to Faraday's law. Calculated corrosion patterns were compared with corrosion damage observed at the surface of the probe after a series of stringent tests. The capability of the probe to measure anodic current densities under CP, without requiring interruption, was demonstrated in high resistivity aqueous solution. The pattern of calculated metal loss correlated well with corrosion products distribution observed at the array surface. Working principles of the probe are explained in terms of electrochemistry.

• 한국표면공학회지
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• 제36권4호
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• pp.301-306
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• 2003

Multilayered WC-Ti/suv $1-x/Al_{x}$ N coatings were deposited on AISI D2 steel using cathodic arc deposition (CAD) method. These coatings contain structural defects such as pores or droplets. Thus, the substrate is not completely isolated from the corrosive environment. The growth defects (pores, pinholes) in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion behavior of the coatings was studied in deaerated 3.5 wt.% NaCl solution using electrochemical techniques (potentiodynamic polarization test) and surface analyses (GDOES, SEM, AES, TEM). The porosity was calculated from the result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the $WC-Ti_{0.6}$ $Al_{0.4}$ N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and lowering the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion mechanisms can be classified into two basic categories: localized corrosion and galvanic corrosion.

• Corrosion Science and Technology
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• 제17권5호
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• pp.231-241
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• 2018

Atmospheric corrosion is generally an electrochemical degradation process of metal. It can be caused by various corrosion factors of atmospheric component, weather, and air pollutants. Moisture, particles of sea salts, and sulfur dioxide are major factors in atmospheric corrosion. Galvanizing coating is one of the most efficient ways to protect iron from corrosion by zinc plating on the surface of the iron. Galvanized steels are being widely used in automobiles, building structures, roofing, and other industrial structures due to their high corrosion resistance compared to bare iron. Atmospheric corrosion of galvanized steel has shown complex corrosion behavior depending on coating process, coating thickness, atmospheric environment, and air pollutants. In addition, different types and kinds of corrosion products can be produced depending on the environment. Lifespan of galvanized steels is also affected by the environment. Therefore, the objective of this study was to determine the corrosion behavior of galvanized steel under atmospheric corrosion at six locations in Korea. When the exposure time was increased, content of zinc from GA surface decreased while contents of iron and oxygen tended to increase. On the other hand, content of iron was constant even after 36 months of exposure of GI.

• Corrosion Science and Technology
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• 제20권3호
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• pp.105-111
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• 2021

In oxidizing nitric acid solutions, stainless steel undergoes intergranular corrosion accompanied by grain dropping and changes in the corrosion rate. For the safe operation of reprocessing plants, this mechanism should be understood. In this study, we constructed a three-dimensional computational model using a cellular automata method to simulate the intergranular corrosion propagation of stainless steel. The computational model was constructed of three types of cells: grain (bulk), grain boundary (GB), and solution cells. Model simulations verified the relationship between surface roughness during corrosion and dispersion of the dissolution rate of the GB. The relationship was investigated by simulation applying a constant dissolution rate and a distributed dissolution rate of the GB cells. The distribution of the dissolution rate of the GB cells was derived from the intergranular corrosion depth obtained by corrosion tests. The constant dissolution rate of the GB was derived from the average dissolution rate. Surface roughness calculated by the distributed dissolution rates of the GBs of the model was greater than the constant dissolution rates of the GBs. The cross-sectional images obtained were comparable to the corrosion test results. These results indicate that the surface roughness during corrosion is associated with the distribution of the corrosion rate.

• Corrosion Science and Technology
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• 제9권6호
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• pp.289-293
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• 2010

To investigate the corrosion behavior of tools steel surface in various coating film, the surface of hard coated Ti-Zr-N film on the tool steel by using magnetron-sputtering methods was researched using various experimental methods. STD 61 steels were manufactured by using vacuum furnace and solutionized for 1hr at $1050^{\circ}C$. Steel surface was coated with Ti-Zr-N film at $150^{\circ}C$ and 100W for 1h by using DC-sputtering equipment. Surface characteristics of Ti-Zr-N film coated specimens were investigated by OM, XRD, FE-SEM and nano-scratch tester. And corrosion behaviors of the coated specimen were investigated by polarization test and electrochemical impedance spectroscopy(EG&G Co, PARSTAT 2273. USA). It was found that Ti-Zr-N film coated sample had a thick coated layer and showed a good wear resistance and corrosion resistance of surface compared with ZrN and TiN coated sample. The corrosion resistance and mechanical property of Ti-Zr-N film coated STD 61 alloy increased as sputtering time increased.