• Title, Summary, Keyword: Galvanic corrosion

Search Result 173, Processing Time 0.04 seconds

A Study on the Corrosion of Al-Alloy Propeller Used for a Coasting Vessel (연안 선박용 Al합금 프로펠러의 부식에 관한 연구)

  • LIM, Uh-Joh;PARK, Hee-Ok;YUN, Byoung-Du
    • Journal of Fisheries and Marine Sciences Education
    • /
    • v.15 no.2
    • /
    • pp.176-183
    • /
    • 2003
  • Recently, with the tendency of lightening, high-strength and high-speed in the marine industries such as marine structures, ships and propellers, it is rapidly enlarged the use of the aluminium alloy. Therefore, there occurs much interest in the study on corrosion characteristics of aluminium alloy. This paper was studied on the corrosion characteristics of Al-Mg alloy propeller used for a coasting vessel. Under the various pH of marine environment, the corrosion test of Al-Mg alloy was carried out. And thus polarization resistance, corrosion potential, and current density behavior of Al-Mg alloy and galvanic corrosion behavior of Al-brass and Al-Mg alloy coupled Al 5086 and SS 400 for hull were investigated. The main results are as following: 1. The corrosion potential of Al-brass propeller is more nobel than materials for hull, but that of Al-Mg alloy propeller is low or similar to materials for hull. Therefore, the galvanic corrosion of hull due to Al-Mg propeller don't occur. 2. The polarization resistance of Al-Mg alloy in sea water of pH 4 is highest, and corrosion current density of Al-Mg propeller is the most controlled. 3. As pH value decreases, potential showed Evans polarization diagram approaches cathodic potential. The corrosion current density of Al-Mg alloy is controlled to anodic reaction rate, therefore, the corrosion reaction of Al-Mg alloy is anodic control.

Critical Influence of Rivet Head Height on Corrosion Performance of CFRP/Aluminum Self-Piercing Riveted Joints

  • Karim, Md Abdul;Bae, Jin-Hee;Kam, Dong-Hyuck;Kim, Cheolhee;Park, Yeong-Do
    • Corrosion Science and Technology
    • /
    • v.18 no.3
    • /
    • pp.92-101
    • /
    • 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.

A Study on the Protection of the Bare and Painted Steel Plates (아연 양극에 의한 도장강판과 나강판의 방식 연구)

  • 문경만;김종신;김진경
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.17 no.1
    • /
    • pp.55-65
    • /
    • 1993
  • Galvanic protection method is one the cathodic protection methods and is mostly used for corrosion prevention of heat exchangers and ship's hull. In this paper, it was investigated that how cathodic potential distribution was varied with according to the bare and painted steel plates in case of galvanic anode protection. The results obtained above were as follows. 1. Cathodic potential distribution of a painted steel plate was smoothed than that of the bare steel plate all over the cathodic surface area. 2. It was shown that polarization potential of the bare steel plate was somewhat shifted to negative potential, on the contrary that of the painted steel plate was somewhat shifted from negative potential to positive potential as time gone by beginning of galvanic anode method. 3. The applied current density in order to maintain constant protection potential(-770mv SCE) in the painted steel plate was less than that of the bare steel plate because of the high resistance polarization of the painted steel plate. 4. It was suggested that required number and life-time of anode for galvanic anode protection could be decided easily with corrosion prevention coefficient obtained by experimental data.

  • PDF

A Electrochemical Study on the Effect of Post-Weld Heat Treatment about Corrosion Resistance Property of SS400 Steel for Ship's Materials (선박재료용 SS400강의 내식성에 대한 용접후열처리효과에 관한 전기화학적 연구(I))

  • 김진경
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.23 no.6
    • /
    • pp.806-813
    • /
    • 1999
  • The effect of Post-Weld Heat Treatment(PWHT) of SS400 Steel was investigated with parameters such as micro vickers hardness corrosion potential polarization behaviors galvanic current Al anode generating current Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM)by PWHT is lower than that of each parts by Non Post-Weld Heat Treatment(NPWHT) However hardness of WM of HAZ part was the highest among those three parts and HAZ area were also acted as cathode without any case of heat treatment. Potential difference between each three parts by PWHT was also smaller compared to NPWHT. Therefore it is suggested that Corrosion resistance property is increased by PWHT. However both Al anode generating current and anode weight loss was also decreased by PWHT compared to NPWHT when SS400 steel is cathodically protected by Al anode.

  • PDF

Electrochemical Random Signal Analysis during Localized Corrosion of Anodized 1100 Aluminum Alloy in Chloride Environments

  • Sakairi, M.;Shimoyama, Y.;Nagasawa, D.
    • Corrosion Science and Technology
    • /
    • v.7 no.3
    • /
    • pp.168-172
    • /
    • 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.

A Study of Localized Corrosion Mechanisms in the Multilayered Coatings by Cathodic Arc Deposition (음극아크증착법으로 합성한 다층박막의 국부부식 기구에 관한 연구)

  • 김호건;안승호;이정호;김정구;한전건
    • Journal of the Korean institute of surface engineering
    • /
    • v.36 no.4
    • /
    • pp.301-306
    • /
    • 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 CHARACTERISTICS BETWEEN IMPLANT FIXTURE AND ABUTMENT SCREW (임플랜트 고정체와 지대나사간의 부식특성에 관한 연구)

  • Kee, Su-Jin;Kweon, Hyeog-Sin;Choe, Han-Cheol
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.38 no.1
    • /
    • pp.85-97
    • /
    • 2000
  • The purpose of this study was to compare the corrosion characteristics between implant fixture and two types of abutment screw ; gold screw, titanium screw. The anodic polarization behavior, the galvanic corrosion behavior, and the crevice corrosion behavior of prepared samples were investigated using potentiostat and scanning electron microscope. The results were as follows: 1. Anodic polarization behavior of samples; The primary passivation potential of implant fixture was -420mV, implant abutment was -560mV. titanium screw was -370mV and gold screw was -230mV. All samples were shown to have a high corrosion potential and good formation of passive film. The critical passive current density of gold screw was higher than that of other samples and the sample of gold screw showed a unstable passive film formation at passive region. 2. Galvanic corrosion behavior of samples; Contact current density between implant fixture and titanium screw showed $8.023{\times}10^{-5}C/cm^2$. Contact current density between implant fixture and gold screw showed $5.142{\times}10^{-5}C/cm^2$. 3. Crevice corrosion behavior of samples; The crevice corrosion resistance of sample using titanium screw was higher than that of sample using gold screw, and a severe corrosion morphologies were observed at the fixture-screw interface by the scanning electron microscope.

  • PDF

A Study on the Corrosion Rehavior and Mechanical Property by SSRTTest of Welding Part of RE36 Steel for Marine Structure (해양구조물 RE36강의 용접부 부식거동 및 SSRT법에 의한 기계적 특성에 관한 연구)

  • 김종성;김진경;김종호;이명훈;김영식;문경만
    • Journal of the Korean Society of Marine Engineering
    • /
    • v.24 no.4
    • /
    • pp.460-469
    • /
    • 2000
  • A study on the corrosion behavior of RE36 steel for marine structure was investigated with parameters such as micro-Vickers hardness, corrosion potential and corrosion current density measurement of weld metal(WM), base metal (BM) and heat affected zone(HAZ), Al anode generating current and Al anode weight loss quantity in case of cathodic protection. And we carried out slow strain rate test(SSRT) in order to research mechanical properties such as stress at maximum load, percent strain, time to fracture and strain to failure ratio etc and to find out limiting cathodic polarization potential for hydrogen embrittlement with applied cathodic polarization potential. Hardness of HAZ part was the highest among those three parts and also galvanic corrosion susceptibility was the highest in HAZ part among those three parts due to the lowest corrosion potential than other parts. However corrosion current density was the highest in WM part among those three parts. And the optimum cathodic polarization potential showing the best mechanical properties obtained by SSRT method with applied constant cathodic potential was from - 770mV to - 875mV(SCE). However it is suggested that limiting cathodic polarization potential indicating hydrogen embrittlement on the mechanical properties was under - 900mV(SCE).

  • PDF

A Study on the Application of FRP Hybrid Bar to Prevent Corrosion of Reinforcing Bar in Concrete Structure (콘크리트구조물 중의 철근 부식 저감을 위한 FRP Hybrid Bar의 적용성 연구)

  • Lee, Seung-Tae;Park, Kwang-Pil;Park, Ki-Tae;You, Young-Jun;Seo, Dong-Woo
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.20 no.5
    • /
    • pp.559-568
    • /
    • 2019
  • Recently, the infrastructure of the marine environment has been increasing. Therefore, there has been increasing interest in increasing the durability of structures. The FRP Hybrid Bar with improved durability against corrosion was developed in recent years. On the other hand, studies that evaluate the corrosion resistance are insufficient. In this study, the corrosion resistance according to the type of rebar in concrete was assessed and analyzed. The experiment used steel bars and FRP Hybrid Bar. The corrosion test method was a galvanic current and half-cell potential method. The accelerated corrosion test was carried out by four levels (0%, 1.5%, 3%, and 6%) of chloride added to the concrete. The galvanic current measurements revealed no corrosion current in the FRP Hybrid Bar. The half-cell measurement also showed the corrosion resistance of the FRP Hybrid Bar. Therefore. FHB can be used as an alternative steel for structures where a marine environment and steel corrosion are predicted.

The Aqueous Corrosion Characteristics of Catenary Materials of Electric Railway System (전차선로 가선재의 수용액 부식 특성)

  • 김용기;장세기;조성일;이재봉
    • Journal of the Korean Society for Railway
    • /
    • v.4 no.2
    • /
    • pp.62-70
    • /
    • 2001
  • Pure copper, Cu-1.1wt%Cd and ACSR(Aluminum Conductor Steel Reinforced) have been used as catenary materials of the electric railway system. Since these materials may be exposed to the corrosive environments like polluted air, acid rain and sea water, it is important to investigate the corrosion rates in various corrosive environments. The aqueous corrosion characteristics of catenary materials in aerated acid, neutral and alkali solutions were studied by using immersion corrosion tests, electrochemical measurements and analytical techniques. In order to examine corrosion characteristics according to the dissolved oxygen content, pH, chloride ion concentration ion, and the addition of Cd to Cu, a series of tests such as potentiodynamic polarization, a.c impedance spectroscopy and galvanic corrosion tests were carried out with these materials. Results showed that the addition of Cd to Cu and chloride ion in the solution have an adverse effects on the resistance to corrosion. Additionally, Galvanic currents between Al and steel wires of ACSR were confirmed by using ZRA(zero resistance ammeter) method.

  • PDF