• Title/Summary/Keyword: Surface corrosion

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Improvement of the Corrosion Resistance of PVD Hard Coating/Substrate Systems - Recent Developments -

  • Jehn, Hermann A.;Kang, Sung-Goon
    • Journal of the Korean institute of surface engineering
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    • v.32 no.3
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    • pp.472-483
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    • 1999
  • Hard coatings playa continuously increasing role in the field of tribology as well as for decorative applications. In both areas they are often also exposed to corrosive media. While especially hard nitride coatings show a high corrosion resistance for themselves, hard $coating_strate systems may suffer from a severe corrosion attack due to the defects in the coating structure (pores, pinholes) resulting from the PVD-typical film morphology. While a huge number of investigations cover the tribological properties, only limited studies deal with the corrosion behavjour of coating substrate systems and attempts are made to improve their corrosion resistance. The present paper shortly describes the corrosion mechanisms and repots characteristic examples of the system behaviour. Special emphasis is laid on recent investigations to improve the corrosion resistance by alloying, interlayers or multilayered coating structures.es.

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Corrosion Characteristics of Aluminum Die Casting Alloys with Different Scrap Charge Rate (스크랩 장입 비율에 따른 다이캐스팅용 알루미늄 합금의 부식 특성)

  • Kim, Jun-Ho;Lee, Seung-Hyo
    • Journal of the Korean institute of surface engineering
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    • v.53 no.6
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    • pp.322-329
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    • 2020
  • The utilization of aluminum scrap is a subject of great importance in terms of reducing energy consumption and environmental protection. However, aluminum scrap contains impurities, which can degrade the properties of aluminum alloy, especially corrosion resistance. This study examines the effect of scrap charge rate of aluminum alloys about microstructures and corrosion characteristics. According to the metallographic examinations, Mg2Si tended to become coarser and its uniformity was decreased by increasing aluminum scrap charge rate. The immersion test exhibited corrosion progressed through the eutectic areas due to micro-galvanic interactions. Electrochemical measurements revealed that excess aluminum scrap could reduce the intergranular corrosion resistance of aluminum alloys. Results showed that the scrap charge rate is important factor in the design of corrosion resistance of aluminum die casting alloys.

Corrosion Behavior of Boron-Carbon-Nitride Films Synthesized by Magnet Sputtering (스퍼터링법으로 합성한 BCN 박막의 내식성)

  • Byon E.;Son M. S.;Lee G. H.;Kwon S. C.
    • Journal of the Korean institute of surface engineering
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    • v.36 no.3
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    • pp.229-233
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    • 2003
  • Boron-Carbon-Nitrogen (B-C-N) system is an attractive ternary material since it has not only an extremely high hardness but also a number of other prominent characteristics such as chemical inertness, elevated melting point, and low thermal expansion. In this paper, the corrosion behavior of B-C-N thin films in aqueous solution was investigated B-C-N films with different composition were deposited on a platinum plate by magnetron sputtering in the thickness range of 150-280 nm. In order to understand effect of pH of solutions, $BC_{2.\;4}N$ samples were immerged in 1M HCl, 1M NaCl, and 1M NaOH solution at 298k, respectively. BCN samples with different carbon contents were exposed to 1M NaOH solutions to investigate effect of chemical composition on corrosion resistance. Corrosion rates of samples were measured by ellipsometry, From results, optical constant of $BC_{2,\;4}N$ films was found to be $N_2=2.110-0.295i$. The corrosion rates of $Bi_{1.\;0}C_{2.\;4}N_{1.\;0}$ films were NaOH>NaCl>HCl in orders. With increasing carbon content in B-C-N films, the corrosion resistance of B-C-N films was enhanced. The lowest corrosion rate was obtained for $B_{1.\;0}C_{4.\;4}N_{1.\;9}$ film.

Effect of Heat Treatment on Corrosion Resistance of Zn-Mg-Al Alloy Coated Steel

  • Il Ryoung Sohn;Tae Chul Kim;Sung Ju Kim;Myung Soo Kim;Jong Sang Kim;Woo Jin Lim;Seong Mo Bae;Su Hee Shin;Doo Jin Paik
    • Corrosion Science and Technology
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    • v.23 no.4
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    • pp.283-288
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    • 2024
  • Hot-dip Zn-Mg-Al coatings have a complex microstructure consisting of Zn, Al, and MgZn2 phases. Its crystal structure depends on alloy content and cooling rates. Microstructure and corrosion resistance of these coatings might be affected by heat treatment. To investigate effect of heat treatment on microstructure and corrosion resistance of Zn-Mg-Al coatings, Zn-1.5%Mg-1.5%Al coated steel was heated up to 550 ℃ at a heating rate of 80 ℃/s and cooled down to room temperature. At above 500 ℃, the ternary phase of Zn-MgZn2-Al was melted down. Only Zn and MgZn2 phases remained in the coating. Heat- and non-heat-treated specimens showed similar corrosion resistance in Salt Spray Test (SST). When a Zn-3.0%Mg-2.5%Al coated steel was subjected to heat treatment at 100 ℃ or 300 ℃ for 200 h and compared with GA and GI coated steels, the microstructure of coatings was not significantly changed at 100 ℃. However, at 300 ℃, most Al in the coating reacted with Fe in the substrate, forming a Fe-Al compound layer in the lower part of the coating. MgZn2 was preferentially formed in the upper part of the coating. As a result of SST, Zn-Mg-Al coated steels showed excellent corrosion resistance, better than GA and GI.

Corrosion Damage Characteristics of STS 304 for the Nuclear Power Plant with Chemical Decontamination Conditions in Permanganic and Oxalic Acid (과망간산과 옥살산 화학제염 공정 시 원전기기용 STS 304 의 부식 손상 특성)

  • Han, Min-Su;Jung, Kwang-Hu;Yang, Ye-Jin;Park, Il-Cho;Kim, Ki-Chul;Seo, Bum-Chul;Park, Ju-Hyun;Kim, Seong-Jong
    • Journal of the Korean institute of surface engineering
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    • v.50 no.4
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    • pp.251-258
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    • 2017
  • This study was carried out with solution temperature variables of $75^{\circ}C$ and $90^{\circ}C$ for STS 304, which is a nuclear equipment material, in order to determine the corrosion damage behavior in chemical decontamination process using permanganic acid and oxalic acid. Then electrochemical polarization experiment, weight loss measurement, surface morphology observation and surface damage depth were measured every cycle of the decontamination process to analyze the degree of corrosion damage. As a result, the corrosion current density, weight loss, and surface damage increased as the decontamination process cycle increased, and the corrosion damage of STS 304 tended to increase. Few ${\mu}m$ pitting damage was observed on the surface observation. In 5 cycle, the elongated wormhole-type pitting damage appeared, leading to relatively large surface damage. However, there was no significant difference in the degree of surface damage resulting from the increase in the temperature of the chemical decontamination solution.

The Effects of Processing Parameters on Surface Hardening Layer Characteristics of Low Temperature Plasma Nitriding of 316L Austenitic Stainless Steel (316L 오스테나이트계 스테인리스강의 저온 플라즈마질화처리시 공정변수가 표면경화층 특성에 미치는 영향)

  • Lee, Insup
    • Journal of the Korean institute of surface engineering
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    • v.52 no.4
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    • pp.194-202
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    • 2019
  • A systematic investigation was made on the influence of processing parameters such as gas composition and treatment temperature on the surface characteristics of hardened layers of low temperature plasma nitrided 316L Austenitic Stainless Steel. Various nitriding processes were conducted by changing temperature ($370^{\circ}C$ to $430^{\circ}C$) and changing $N_2$ percentage (10% to 25%) for 15 hours in the glow discharge environment of a gas mixture of $N_2$ and $H_2$ in a plasma nitriding system. In this process a constant pressure of 4 Torr was maintained. Increasing nitriding temperature from $370^{\circ}C$ to $430^{\circ}C$, increases the thickness of S phase layer and the surface hardness, and also makes an improvement in corrosion resistance, irrespective of nitrogen percent. On the other hand, increasing nitrogen percent from 10% to 25% at $430^{\circ}C$ decreases corrosion resistance although it increases the surface hardness and the thickness of S phase layer. Therefore, optimized condition was selected as nitriding temperature of $430^{\circ}C$ with 10% nitrogen, as at this condition, the treated sample showed better corrosion resistance. Moreover to further increase the thickness of S phase layer and surface hardness without compromising the corrosion behavior, further research was conducted by fixing the $N_2$ content at 10% with introducing various amount of $CH_4$ content from 0% to 5% in the nitriding atmosphere. The best treatment condition was determined as 10% $N_2$ and 5% $CH_4$ content at $430^{\circ}C$, where the thickness of S phase layer of about $17{\mu}m$ and a surface hardness of $980HV_{0.1}$ were obtained (before treatment $250HV_{0.1}$ hardness). This specimen also showed much higher pitting potential, i.e. better corrosion resistance, than specimens treated at different process conditions and the untreated one.

Corrosion resistance at high temperature condition of Cr Films Formed on hot-dip Al-Si plated steel sheet (용융Al-Si도금 강재에 형성한 Cr 막의 고온 환경 중 내식특성)

  • Gang, Min-Ju;Lee, Seung-Hyo;Lee, Myeong-Hoon
    • Journal of the Korean institute of surface engineering
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    • v.55 no.6
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    • pp.448-459
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    • 2022
  • Generally, steel is the most commonly used in the industry because of good strength, processability and cost-effectiveness. Steel can be surface-treated such as coating or used as an alloy by adding elements such as Cr, Ni, Zr, and Al to increase corrosion resistance. However, even if steel is used in same environment corrosion resistance is sharply lowered when it is exposed to a high temperature for a fixed or extended period of time due to an overload or other factors. In particular, the use of hot-dip aluminized plated steel, which is used in high-temperature atmospheres, is increasing due to the surface Al2O3 oxide film. This steel necessitates an urgent solution as issues of corrosion resistance limitations often appear. It is an important issue that not only cause analysis but also the research for the surface treatment method that can be solved. Thus, in this study, Cr in which it is expected to be effective in corrosion resistance and heat resistance attempted to deposit on hot dip aluminized plated steel with PVD sputtering. And it was possible to present the surface treatment application of various types of industrial equipment exposed to high temperature and basic design guidelines for use by confirming the corrosion resistance of hot dip Al-Si plated steel with Cr film deposited at high temperature.

Effect of the Amount of CH4 Content on the Characteristics of Surface Layers of Low Temperature Plasma Nitrocarburizied STS 204Cu Stainless Steel (STS 204Cu 스테인리스강의 저온 플라즈마 침질탄화 처리 시 CH4 가스 함량에 따른 경화층 (S-Phase) 거동)

  • Lee, Insup;Kim, Hojun
    • Journal of the Korean institute of surface engineering
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    • v.51 no.1
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    • pp.54-61
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    • 2018
  • Plasma Nitriding treatment was performed on STS 204Cu stainless steel samples at a temperature of $400^{\circ}C$ for 15 hours with varying $N_2$ content as 10%, 15% and 25%. Regardless of the content of $N_2$, S-Phase which is a hardened layer of Nitrogen (N) supersaturated phase, was formed in the surface of plasma treated samples. When $N_2$ content was 25%, the thickness of the hardened layer reached up to about $7{\mu}m$ and the surface hardness reached a value of $560Hv_{0.05}$, which is about 2.5 times higher than that of untreated sample (as received $220Hv_{0.05}$). From potentiodynamic polarization test, it was observed that compared to as received sample, the corrosion potential and the corrosion current density of the plasma treated samples were decreased regardless of the $N_2$ content, but the corrosion resistance was not increased much due to the precipitation of $Cr_2N$. On the other hand, pitting potential of the samples treated with 10% and 15% $N_2$ was higher than that of as received sample, however, the samples treated with 25% exhibited a lower pitting potential. Therefore, 10% $N_2$ content was selected as optimum plasma nitriding condition and to further increase both the thickness and surface hardness and the corrosion resistance of the hardened layer, different $CH_4$ content such as 1%, 3% and 5% was introduced into the plasma nitriding atmosphere. With 1% $CH_4$, the thickness of the hardened layer reached up to about $11{\mu}m$ and the surface hardness was measured as about $620Hv_{0.05}$, which is about 2.8 times that of as received sample. And the corrosion resistance of the plasma treated sample by using 1% $CH_4$ was improved significantly due to much higher pitting potential, and lower corrosion current density. When the $CH_4$ content was more than 1%, the thickness and surface hardness of the hardened layer decreased slightly and the corrosion resistance also decreased.

Corrosion Behavior of Titanium for Implant in Simulated Body Fluids (인공 체액 조건에서 임플랜트용 티타늄 소재의 부식 특성)

  • 이중배;최기열
    • 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.

A Study on the Fracture Surface Growth Behavior of Steel used for Frame of Vehicles by Corrosion Fatigue (자동차 프레임용 강재의 부식피로에 의한 파면성장거동에 관한 연구)

  • Lee, Sang-Yoel;Im, Jong-Mun;Im, U-Jo;Lee, Jong-Rak
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.28 no.1
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    • pp.61-70
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    • 1992
  • In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane bending fatigue tester in marine environment and investigated fracture surface growth behavior of base metal and heat affected zone corrosion fatigue. The main results obtained are as follows: 1) Fracture surface growth of heat affected zone (HAZ) is delayed more than that of base matel (BM), and they tend to faster in seawater than in air. 2) Corrosion sensitivity to corrosion fatigue life of HAZ is more susceptible than that of BM. 3)In the case of the corner crack by corrosion fatigue, the correlation between the propagation rate of fracture surface area(dA/dN) and stress intensity factor range(ΔK) for SAPH45 are applied to Paris rule as follows: dA/dN=C(ΔK) super(m) where m is the slope of the correlation, and is about 6.60-6.95 in air and about 6.33-6.41 in seawater respectively.

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