• Corrosion Science and Technology
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• 제16권1호
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• pp.38-47
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• 2017

Due to various types of Zn coatings for many decades for various applications, it is imperative to study and compare their corrosion resistance properties of some of these. Here, we introduce a systematic methodology for evaluation and validation of corrosion protection properties of metallic coatings. According to this methodology, samples are were exposed in an advanced cyclic corrosion test chamber according to ISO 14993, and removed at the end of each withdrawal for respective corrosion and electrochemical characterization to evaluate both barrier and galvanic protection properties. Corrosion protection properties of coatings were evaluated by visual examination according to ISO 10289, mass loss and subsequent corrosion rate measurements, electrochemical properties, and advanced electrochemical scanning techniques. In this study, corrosion protection properties of a commercial zinc rich coating (ZRC) on AISI 1020 mild steel substrates were evaluated and benchmarked against hot dip galvanized (HDG). Results were correlated, and corrosion protection capabilities of the two coatings were compared. The zinc rich coating performed better than hot dip galvanized coating in terms of overall corrosion protection properties, according to the exposure and experimental conditions used in this study. It proved to be a suitable candidate to replace hot dip galvanized coatings for desired applications.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.17-17
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• 2012

Magnesium alloys exhibit many attractive properties such as low density, high strength/weight ratio, high thermal conductivity, very good electromagnetic features and good recyclability. However, most commercial magnesium alloys require protective coatings because of their poor corrosion resistance. Attempts have been made to improve the corrosion resistance of the Mg alloys by surface treatments, such as chemical conversion coatings, anodizing, plating and metal coatings, are commonly applied to magnesium alloys in order to increase the corrosion resistance. Among them, chemical conversion coatings are regarded as one of the most effective and cheapest ways to prevent corrosion resistance. In this study, zinc phosphate conversion coatings on various Mg alloys have been developed by selecting proper phosphating bath composition and concentration and by optimizing phosphating time, temperature. Morphology, coatings composition, corrosion resistance, adhesion and its formation and growth mechanism of the zinc phosphate conversion coatings were studied. Results have shown some attractive properties such as simplicity in operation, significantly increased corrosion protective property. However, adhesions between coatings and substrate and also between coatings and paint are still not satisfied. Resolving the problems and understanding the mechanism of phosphating process are targets of our study.

• Corrosion Science and Technology
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• 제3권3호
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• pp.107-111
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• 2004

Corrosion resistance of coating system consisting of zinc-rich primer (ZRP) and topcoat based on polyurethane resin with the presence of 3-aminopropyl-triethoxysilan (APS) and 2-(benzothialylthio) succinic acid (BSA) was studied by electrochemical impedance and wet adhesion. The interface metal/primer/topcoat was analyzed by scanning electronic microscopy. It was found that the presence of APS and BSA improved adhesion and barrier property of the topcoats.

• Corrosion Science and Technology
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• 제16권5호
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• pp.241-246
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• 2017

The comparative results of corrosion testing in humid tropical atmosphere in rural and coastal areas for hot dipped zinc coatings are presented below. The test was conducted in outdoor conditions over a period of five years. The mass loss and other performance characteristics of two types of zinc coatings were evaluated, analysed and discussed in relation to the climatic and environmental parameters. The corrosion rates of the coatings exposed to coastal conditions were about three times higher than the corrosion rates appreciated in rural conditions. The data demonstrates that the corrosion process obeys an equation of the form $M=At^n$, where M is the loss of metal and t is the time of exposure. A and n are constants which values depend on the environmental characteristics and the physicochemical behavior of the corrosion products respectively. Corrosion is strongly influenced by atmospheric time of wetness (TOW) and airborne salinity. The nature and composition of corrosion products are also considered. Simonkolleite, a major crystalline phase, was found in the zinc corrosion products exposed to coastal conditions, while zinc hydroxide and zinc hydrosulfate are easily found in rural settings.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.322-323
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• 2012

This study discussed the formation of phosphate conversion coatings on AZ31 Mg alloy (AZ31) from the zinc phosphating bath with various concentrations of sodium fluoride (NaF). The effects of NaF on the formation, structure, composition and electrochemical behavior of the phosphate coatings were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) weight balances, open circuit potential (OCP) transients, potentiodynamic polarization curves and immersion test. The coatings were composed of two layers: an outer $Zn_2(PO_4)_3.4H_2O$ (hopeite) crystal layer and an inner amorphous of $MgZn_2(PO_4)_2$. NaF concentration is emphasized to be highly effective in the formation of the hopeite crystal and etching and coating rates. Potentiodynamic polarization and immersion test showed that the coatings formed in the zinc phosphating bath with addition of NaF have much higher corrosion resistance than bare AZ31.

• 한국표면공학회지
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• 제36권1호
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• pp.42-47
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• 2003

Hot-dip galvanizing process is used widely in industry to achieve corrosion resistant coatings. Poor drainage during this process often leads to problems such as icicle formation and bridging In this work, mild steel specimens were hot-dip galvanized. Influence of the addition of bismuth, aluminum and both (bismuth and aluminum) to the zinc bath on the zinc drainage were determined. Bismuth additions improved the drainage significantly. Zinc bath containing 0.1 wt.% Bi and 0.025∼0.05 wt.% Al showed uniformity of coatings. Industrial trials with this bath composition showed reduction in zinc consumption, reduction of ash and dross, and good luster of workpiece.

• Tribology and Lubricants
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• 제14권1호
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• pp.1-6
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• 1998

An experimental study was performed to discover the tribological behaviors of pure tin and zinc coated 52100 bearing steel. Pure tin coatings ranging from 30 nm to 30,000 nm and pure zinc coatings ranging from 500 nm to 52,000 nm were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed for the investigations of the effect of coating thickness on the tribological rolling behavior. Results showed that the existence of optimum film thickness which revealed minimum rolling resistance was discovered for tin and zinc coating. The compatibility of coating material to iron showed no significant effect on the rolling resistance behavior. The hardness of coating material revealed significant influence to the rolling resistance behavior.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1997년도 제26회 추계학술대회
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• pp.51-58
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• 1997

An experimental study was performed to discover the tribological behaviors of pure tin and zinc coated 52100 bearing steel. Pure tin coatings ranging from 30 nm to 30,000 nm and pure zinc coatings ranging from 500 nm to 52,000 nm were produced by a thermal evaporation coating method. Experiments using a thrust ball bearing-typed rolling test-rig were performed for the investigations of the effect of coating thickness on the tribological rolling behavior. Results showed that the existence of optimum film thickness which revealed minimum rolling resistance was discovered for tin and zinc coating. The compatibility of coating matehal to iron showed no significant effect on the rolling resistance behavior. The hardness of coating material revealed significant influence to the rolling resistance behavior.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.255-255
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• 2011

Zinc oxide based thin films have been extensively studied in recent several years because they have very interesting properties and zinc oxide is non-poisonous, abundant and cheap material. ZnO films are employed in different applications like transparent conductive layers in solar cells, protective coatings and so on. Wide industrial application of the ZnO films requires of development of cheap, effective and scalable technology. Typically used technologies don't completely satisfy the industrial requirements. In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photoelectron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Increasing of the oxygen content in the gas mixture during deposition allow to obtain high-resistive protective and insulation coatings with high adhesion to the metallic surface.

• 한국표면공학회지
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• 제25권2호
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• pp.57-65
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• 1992

Increasing demands of high corrosion resistant sheet steels for the automotive body panels have been leading to a tendency toward heavier coatings of electroplated sheet steels. The specimens were prepared from lab-scale electroplating simulator with various coating weights of zinc, zinc-iron and zinc-nickel coated sheet steels and evaluated in the light of the application for the automotive body panels. Corrosion resistances by sacrificial action were improved with increasing coating weights for all electroplated sheet under survey, but blistering resistances of pure zinc coated sheet steels were not as much. On the other hand, the adhesions of heavy alloy coatings showed poor powdering performances by the external compressive or tensile forces.