Ion Selective Permeability of Rust Layers on Low Alloy Steels under the Chloride Ion Existence

Noda, Kazuhiko,Nishimura, Toshiyasu,Masuda, Hiroyuki,Kodama, Toshiaki 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.1

The ion selective permeability of the rust on carbon steel and Fe-Co and Fe-Ni low alloy steel was investigated by measurement of membrane potential to evaluate the characteristics of the rust layer on low alloy steels. These steels were selected as testing materials because they were thought to be basic alloys of weathering steels for the use in coastal environments, A rust film was formed on two kinds of low alloy steels (Fe-Co and Fe-Ni steel) by corrosion cycle tests that imitated the atmospheric corrosion environment in the seashore. In the case of the carbon steel, the rust layer on it had anion selective permeability. On the other hand, in spite of the rust layer on the carbon steel was anion selective, it was found out that the permeability changed to the cation selective by the result of determining the membrane potential of the rust on Fe -Co low alloy steel. The addition of a few Co was effective for decreasing the corrosion rate, because the rust layer of the cation selective was obstructed the invasion of chloride. The addition of Ni was known to be effective in decreasing corrosion rate of steel, despite their anion selective nature in rust layer. Alternative mechanism other than ion selectivity is required for the explanation of inhibition by Ni. The tendency of the membrane potential measurement of rust layers on all samples formed by corrosion cycle test was same as the case of rust films formed by exposure tests.

Cr, Co, Cu, Ni와 Ca의 첨가에 따른 지하매설배관의 전기화학적 특성에 관한 연구

최윤석,신동호,심재주,김정구 대한금속재료학회 2005 대한금속·재료학회지 Vol.43 No.1

Aqueous corrosion characteristics of low carbon steel with small amounts of Cr, Co, Cu, Ni and Ca, in synthetic groundwater was studied by electrochemical corrosion tests (potentiodynamic test and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. Neither carbon steel nor newly alloyed steels showed passive behavior in this synthetic groundwater. Newly alloyed steels, containing Cr-Co, Cr-Cu-Ni and Cr-Cu-Ni-Ca showed higher corrosion resistance than carbon steel in the potentiodynamic tests. EIS measurements showed that the Nyquist plot presented two time constants. The high frequency resistance component (R_(rsut)) and low frequency resistance component (R_(et)) were affected by the alloying elements. The polarization resistance (RP= R_(et) +Ra) of steels could be clearly ranked as Cr-Cu-Ni-Ca steel >> Cr-Cu-Ni steel > Cr-Co steel > carbon steel. Results of surface analyses (XPS and EPMA) showed that Cr and Cu were concentrated in the inner region of rust. However, Co and Ni were uniformly distributed all over the rust layer. These alloying elements improved corrosion resistance of low alloy steel in synthetic groundwater. Especially, Cr-Cu-Ni-Ca steel had the lowest corrosion rate due to the inner rust film formation during the initial stage of corrosion, which suggested a potential for substituting carbon steel in soil environment (Received October 29, 2004)

무도장 고내후성강을 이용한 건축물 외벽 마감의 시트간 접합방식유형과 방수성능평가에 관한 연구

양정필 대한건축학회 2003 대한건축학회논문집 Vol.19 No.1

The main purpose of this study is to investigate and evaluate the joint types of weathering steel derails in exterior wall. Usually rust influence bad impact against steel. So proper treatments against rust are necessary need in constructing buildings. But in case of weathering steel, rust(stabilized rust) rather protect steel and increase durability. The results of study are as follows: 1. The color of rust on weathering steel surface is changed onto dark-chocolate color, after serring up the sample model. And the difference of color by directions and parts is gradually reduced. 2. The rust stains on the surface by rebounded rains are not removed. So exterior wall of weathering steel must part from the floor level, about 30㎝. 3. The joint types of weathering steel are divided into 'butt joint type', 'overlapped joint type', and 'folded joint type'. 4. In aspect of waterproof performance, 'overlapped joint type' is superior to any other joint type.

Atmospheric Corrosion Behavior on Low Alloy Steels under Seashore Environment

Noda, Kazuhiko,Yamamoto, Masahiro,Masuda, Hiroyuki,Kodama, Toshiaki 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.3

Atomic force microscope (AFM) measurements and scanning chemical microscopy (SCHEM) were performed for the investigation of atmospheric corrosion behavior of low alloy steels. The high sensitivity profile was determined by AFM for iron surface with droplets of synthetic seawater following the exposure to corrosive atmosphere. Simultaneously with AFM surface potential on iron was detected using a Kelvin force microscope (KFM) system during rusting process. Microvisualization of rusting iron surface is to be demonstrated in this paper in the form of parallel mapping of profile and surface potential distribution using the in-situ measuring technique. At relative humidity (RH) of 40%, growth rate of rusting on iron greatly increased in comparison with the case of RH of 30%. The water condensation in the presence of MgCl₂ is the main reason of the enhanced corrosion rate with increasing of relative humidity. In advance to the rust formation, a zone of less noble potential was detected by KFM around the droplet of synthetic seawater although AFM showed no irregularity in the profile image. It can be explained by this less noble potential that the rusting reaction initiated in the vicinity of the seawater droplet. The efficiency of alloy elements (Ni, Cr) on the atmospheric corrosion morphology was explained by SCHEM system. It has been proven that AFM system combined with KFM and SCHEM sjstem was effective in the investigation of atmospheric corrosion of iron and steel which otherwise was dificult to evaluate by conventional method.

Study on the Initiation of a Thermite Reaction in Aluminum Coated Steel with a High-Velocity Impact

Iman Maroef,남대근,김영석,임영목,David L. Olson,조용준,강남현,박영도,유지훈 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.5

Both theoretical and experimental studies have been performed in order to investigate the feasibility of thermite sparking and the impact of rusted steel on aluminum coated steel. For dry rust, the exothermic reaction occurred at 900 °C while the wet rust ignited an exothermic reaction at 1000 °C. This delayed ignition was attributed to the consumption of energy by the water while in wet rust for phase transformation. The experimental study used a compressed-gas-powered impact-testing apparatus that showed that the dry rusted steel ignited sparking upon colliding with un-coated steel. It was also found that the presence of an aluminum coat generated a higher susceptibility to sparking than colliding with un-coated steel.

Effect of Microstructures on the Corrosion Behavior of Reinforcing Bars (Rebar) Embedded in Concrete

Prvan Kumar Katiyar,Prasanna Kumar Behera,Sudhir Misra,K. Mondal 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.5

This work aims at understanding the effect of microstructures (coarse, medium and fine ferrite–pearlite, martensite andtempered martensite) of a reinforced (rebar) steel developed by various heat-treatments (furnace cooling, air-cooling, forceair-cooling, quenching, and tempering, respectively) on its corrosion behavior in freely aerated 3.5% NaCl + 3.5% FeCl3solution. The impressed current technique was used for forcing corrosion of the rebar, which was embedded in concretecoupon, so that correlation could be drawn between microstructure and corrosion behavior in short duration. Corrosionsusceptibility increased from force air-cooled–quenched–air cooled–furnace cooled–tempered steels. The crack formationin the concrete was directly related to the rust composition and thickness, presence of crack in the rust, alpha/gamma* ratioand critical corrosion amount.

Corrosion Behaviour of DH36 Steel Used for Oil Platform in Splash Zones

( J. G. Liu ),( Y. T. Li ),( B. R. Hou ) 한국부식방식학회(구 한국부식학회) 2015 Corrosion Science and Technology Vol.14 No.4

The splash zone is the most corrosive area of the marine environment, and the corrosion of steel structures exposed in this area is a serious concern. DH36 steel is one of most commonly used steels for offshore oil platforms in China, and its corrosion behaviour in splash zones was studied in this paper. Polarization curves were obtained from the corroded steel exposed in this area while the morphologies and rusts of the rust steel were characterized using scanning electron microscopy and X-ray diffraction. Double rust layers were formed in the splash zone. The inner layer contained magnetite and fine flaky lepidocrocite, and the outer layer was composed of accumulated flaky lepidocrocite and a small amount of goethite. In the wet period, the iron dissolved and reacted with lepidocrocite, and magnetite appeared, while the magnetite was oxidized to lepidocrocite again during the dry period. Electrochemical reduction and chemical oxidization cycled in intermittent wetting and drying periods, and magnetite and lepidocrocite were involved in the reduction reaction, leading to serious corrosion.

Effect of Alloying Elements for Low-Alloy Weathering Steels for Structures in Marine/Coastal Atmosphere

Kodama, Toshiaki,Nishimura, Toshiyasu 한국부식방식학회 2002 Corrosion Science and Technology Vol.31 No.2

Low-alloy weathering show poor performance in environments where airborne salinity is high. Recent research on rust and weathering steels has been focused on the rusting mechanism in the presence of chloride and the development of new steels that are resistant in marinelcoastal environments. The paper focuses on 1) crystal structure of iron rust in high salinity, 2) electrochemical reaction of rust and its catalytic properties in chloride media, 3) protective nature of rust of weathering steels, 4) thermochemical aspect of nrsting in chloride environments,.

Experimental Study on Mechanical Properties of Q690 High Strength Steel in Marine Corrosive Environment

Hongchao Guo,Tianqi Lei,Jinguang Yu,Defa Wang,Xiaolei Li 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2

In order to study the mechanical property degradation rule of Q690 high-strength steel in the ocean wave splash area, the rusted specimen is obtained by indoor damp heat surrounding soaking environment corrosion test. The scanning electron microscopy, uniaxial tensile and cyclic loading tests of corroded steel are performed. This paper analyzes the steel from elastic modulus, yield strength, ductility and law of hysteresis degradation under diff erent corrosion cycles and establishes the constitutive model of HSS. The results show that the appearance of HSS is obviously aff ected by the corrosion cycle. With the increase of the corrosion cycle, reddish-brown fl aky corrosion products are formed on the surface of the steel and there are obvious corrosion pits. After 100 days of corrosion, the corrosion rate of steel reached 7.21%; the elastic modulus and yield strength under uniaxial tension load decreased by 10.2% and 4.9%. Under the eff ect of cyclic reciprocating load, the hysteretic energy is reduced by 15.3%; at the same time, the test curve is fi tted by the secondary plastic fl ow model and the Ramberg–Osgood model and it is found that the shape parameter S 1 and the cyclic strengthening coeffi cient K’ are reduced by 20.1% and 10.2%, While the shape parameter S 2 and the cycle strengthening index n’ have no obvious changes.

인공 해수분위기에서 저탄소강의 부식특성에 미치는 합금원소 Cr, Co 및 W의 효과

심재주,유승재,최윤석,김정구,유장용 대한금속재료학회 2003 대한금속·재료학회지 Vol.41 No.12

The aqueous corrosion characteristics of 1% Cr-steel alloyed with small amounts of Co and W, in synthetic seawater was studied by using immersion weight-loss tests, electrochemical corrosion tests (potentiodynamic test and electrochemical impedance spectroscopy (EIS) measurements) and analytical techniques. 1% Cr steels containing Co or W from 0.2 to 0.4 wt.% showed higher corrosion resistance than the 1% Cr steel in the immersion and potentiodynamic tests. EIS measurements showed that the Nyquist plot presented one time constant. Furthermore, the Co- and W-bearing steels present higher Rp values than the 1% Cr steel through all the test period. The better corrosion resistance of the Co-and W-bearing steels is attributed to protectiveness of the surface layer. The corrosion products were examined using electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS). The results of EPMA indicated that Cr was concentrated in the inner region of the rust layer, while Co and W were distributed all over the rust layer. XPS results showed that Co existed as a trivalent oxide in the rust layer and W in the rust appeared in the form of a WO₄ compound.