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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 72 (1986), No. 8

  • Recent Development of Surface Finishing Technology

    pp. 891-898

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  • Influence of Surface Treatment on Performance of Solid Film Lubricants

    pp. 899-903

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  • Precision Mirror Finish of Steel Materials with Electrochemical Abrasive Polishing

    pp. 904-908

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  • Functional Metal Plating

    pp. 911-917

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  • Mechanism of Abnormal Type Alloy Deposition

    pp. 918-923

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  • Approach to the Development of Corrosion Resistance of Fe-Zn Alloy Coating from Corrosion Science

    pp. 924-931

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    The corrosion resistance of zinc and zinc alloy coatings in natural environment depends on the properties of corrosion product layer found on the surface. The type and amount of corrosion products, adhere to the surface, influence the barrier effect of corrosion layer. The amount of zinc hydroxide and basic zinc chloride, Q, could be determined by cyclic cathodic polarization method on the basis of the finding that adherent corrosion products were reduced in response to the electrode potential. A new function of compactness of corrosion layer, C=Q/Icorr., was introduced in order to evaluate the barrier effect of corrosion product layer.
    Nickel was selected as an additional element, which developed the corrosion resistance of Fe-Zn alloy coating, from the values of Icorr. and C determined of corroding zinc specimens in the solution containing iron and other metallic ions.
    1 wt% nickel addition to Fe-Zn alloy coating enhanced the corrosion resistance of coating.
    And a new function of compactness, C, was useful to evaluate the barrier effect of the corrosion product layer for oxygen diffusion.
  • Mass Balance in Diaphragm-type Electroplating Process with Anion Exchange Membrane

    pp. 932-939

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    Diaphragm-type electroplating process with anion exchange membrane has been investigated to prevent the anode oxidation of Fe2+ ion on insoluble anode in Zn-Fe alloy electroplating solution.
    (1) Insoluble anode is separated from electroplating solution with anion exchange membrane, and ion balance between anode compartment and cathode compartment is maintained with ion supplier.
    (2) This process is capable of high current density electroplating up to 100 A/dm2 without any damage of membrane by using sulfuric acid in anode compartment, and membrane potential drop is about 1 V.
    (3) In continuous electroplating pilot line tests, ion balance of electroplating solution is proved to be maintained and this process is effective to prevent the anode oxidation of Fe2+ ion on the insoluble anode.
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  • Effects of Proximate Electrolysis and Gas Bubbles on Voltage Balance of an Electrolytic Cell

    pp. 940-945

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    In the voltage balance of the conventional electrolytic cell the resistance of the electrolyte has the highest occupancy rate of 80. The proximate electrolysis by the fluid support and the insoluble anode effectively reduces this electrolyte resistance. Therefore, highly efficient electrolysis can be achieved by the liquid cushion cell.
    The behavior of the gas evolved on the anode can be analyzed by Bruggeman's equations. In electroplating the gas bubbles cause the unequality of the current density distribution in the cell rather than the cell voltage up.
    In the case of a high current density with narrow electrode gap such as liquid cushion cell of horizontal type the bubble effects on the cell voltage up and the burning of platings can be almost eliminated by the high flow velocity of the electrolyte.
  • Hydrodynamic Analysis of a Continuous Vertical Electro Plating Cell

    pp. 946-953

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    An engineering interest to develop an electroplating cell which assures uniform alloy-plated coatings at high current density and high-speed operation has stimulated this investigation. Many beaker scale studies have been reported about the major influence of electrolyte flow on the electrodeposition of zincbased alloy-plating. Much less is, however, known about the availability of process data obtained from laboratory experiments for scale-up and process design of commercial-size electroplating line. Experiments have been conducted utilizing a high-speed pilot-line, coupled with flow velocity measurements in a hydrodynamic model with a moving endless strip. A process analysis method for a continuous electroplating line through the use of empirical correlations of appropriate dimensionless numbers is advanced. The characteristic quantities for this system are the hydrodynamic equivalent diameter, and in addition the mean relative flow velocity in a coordinate system with the movement of a strip. It is shown that alloy-plating behaviour at a continuous plating cell with fluid injection can be approximated based on relaxation of similitude rule.
  • Structures of Electrodeposited Fe-Zn Alloys

    pp. 954-960

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    Structures of the electrodeposited Fe-Zn alloys from sulphate solutions were investigated by transmission electron microscope, X-ray diffraction and Mossbauer spectroscopy.
    (1) The deposits containing iron in the range of 0.9-17 wt% had hexagonal structures corresponding to the iron-supersaturated eta (η)-phase.
    (2) The deposits containing iron in the range of 18.5-40 wt% had b.c.c. structures similar to the gamma (Γ)-phase, but were different from Γ-phase in the Mossbauer spectra.
    (3) The deposits containing iron more than 50 wt% had b.c.c. structures corresponding to the zinc-supersaturated alpha (α)-phase.
  • Phase Transition of Electrodeposited Fe-Zn Alloy Film by Heating

    pp. 961-967

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    Change in the structure of electrodeposited Fe-Zn alloy films during heating was investigated by using the methods of differential scanning calorimetry and X-ray diffractions. Following results are obtained :
    (1) Exothermic reactions occurred at 150 °C, 210°C and 300°C. These reactions are supposed to be attributed to the phase transition of the electrodeposited film to δ1, Γ, and Γ phases, respectively.
    (2) Corrosion current density decreased afetr heating during 30 min, at 180°C. It can be concluded that this change after heating is concerned with the transition of electrodeposited film to equilibrium phase.
  • Corrosion Resistance and Paintability of Zn-Mn Alloy Plated Steel Sheets

    pp. 968-975

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    Strong interest has been focussed on corrosion-resistant steel by automobile industries to protect auto bodies from corrosion.
    To meet the requirements for corrosion-resistant steel, Zn-Mn alloy electroplated steel has been newly developed.
    Zn-Mn alloys are electrodeposited on the steel sheet from a citric bath consisting of zinc sulfate, manganese sulfate and sodium citrate.
    Corrosion resistance of steel plated with Zn-Mn alloy without painting increased prominently in the range above 20 wt% Mn content, and time to no red rust occurred on the steel plated with 20 g/m2 Zn-Mn alloy up to 1 000 h, when Mn content in deposit. was more than 40 wt% or more.
    This behavior of corrosion resistance without painting are correlated with crystal structures of Zn-Mn alloy ; γ-Mn, manganese solid solution of tetragonal structure, enhances corrosion resistance without painting. The good corrosion resistance results from γ-Mn2O3, corrosion product of Mn, which acts as protective barrier.
    Moreover, as steel plated with Zn-Mn alloy also affords good corrosion resistance after painting, wet adhesion of paint and anti-cratering property, it is possible to use this plated steel sheet for automotive body panels.
  • Effects of Fe-P Upper Layer Coating Weight on Paintability and Corrosion Resistance of Double Layer Alloy Coated Steel Sheets

    pp. 976-983

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    Although Zn base alloy coated steel sheets show good corrosion resistance, their use in the exposed side of auto-bodies is not expected because of their poor phosphatability and paintability compared with those of uncoated cold rolled steel sheets.
    To modify these properties, an Fe-P alloy layer (26 g/m2) is electroplated on Zn base alloy coated steel and double layer alloy coated steel has been developed. The addition of P into the upper Fe layer contributes to the formation of finely packed phosphate crystals in both spray and dip type phosphate treatments. The upper Fe-P layer also helps to suppress the formation of crater form paint defects during the cathodic electrodeposition. Moreover, the Fe-P alloy upper layer reduces blisters at cross cut portions of painted specimens during corrosion tests. When the upper layer coating weight is below 6 g/m2, the corrosion behavior, such as red rust formation and thickness reduction, of the double layer alloy coated steels is similar to that of the single layer Zn alloy coated steels.
  • The Improvements of Smelting and Refining Technologies for Zinc

    pp. 985-988

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  • The Effects of Microstructure and Chemical Compositions of Steels on the Reaction between Iron and Zinc

    pp. 989-996

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    The effects of surface microstructure and chemical compositions of steels on characteristics of Fe-Zn intermetallic phases formed on continuously galvanized steel sheets have been investigated, using ultra low carbon and low carbon steels.
    From a SEM observation, the morphology of Fe-Zn IMP formed at interface between steel and plating layer were classified into three types ; outburst structure, fine granular structure, and pillar-like structure. The formation of the outburst structure was accelerated by decreasing solute carbon content in steels. Phosphorus inhibited this formation when solute carbon was combined with a carbide forming element such as Nb or Ti. The comparison between distribution of Fe-Zn IMP and corresponding steel surface indicated that the outburst structure was given priority to form at the grain boundaries exposed on the steel surface, whereas fine granular structure formed mainly at the surface grain interior.
  • The Relation between the Powdering and the Microstructure of the Coating of Galvannealed Steel Sheets

    pp. 997-1004

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    The structure of the galvannealed coating was studied by etching and measuring the potential time curve for the electro-chemical stripping.
    The formation of Γ phase was found to have the following extreme cases :
    (1) Γ layer is formed along the Zn/Fe boundary, which was typically shown in 1.6% Mn steel.
    (2) Γ grains are scattered in the δ1(c) layer near the Zn/Fe boundary ((δ1+Γ) layer), which is typically shown in P-Nb bearing steel.
    The behavior of cracks in the coating was observed after bending. The cracks were generated from the Γ layer or(δ1+Γ)layer.The cracks propagated most easily in the Γ layer, followed by the(δ1+Γ) layer. The length of crack propagating along the Zn/Fe boundary was mainly dependent upon the thickness of the Γ layer. Therefore, the form of Γ phase was found to affect the powdering behavior.
  • Influence of Microstructure on Corrosion Resistance in Zn-Al Alloy Coating

    pp. 1005-1012

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    The changes in microstructure of Zn-Al alloy coating according to the alloy composition and the cooling rate after coating were investigated, and the influence of microstructure on corrosion properties was discussed.
    1) When the specimens were slowly cooled at 5°C/s after coating, zinc-rich primary phase precipitated in the coatings which contained less than 5%Al. On the other hand, the coating became eutectic structure without primary phase when it contained 5.25.4%Al.
    2) Zn-4.5%Al alloy coatings were cooled at various rates after remelting. When the specimen was cooled at 5°C/s100°C/s, the primary phase precipitated in the coating. The microstructure of the coating became uniform when the specimen was quenched.
    3) The primary phase in the coating deteriorated the corrosion resistance in the salt spray test. The uniform microstructure without primary phase showed the best corrosion resistance.
    4) It is effective to adjust Al content precisely at eutectic composition or to cool coated sheets as rapidly as posible for getting the uniform microstructure and the good corrosion resistance.
  • Black Patina Developed on Zn-Al Alloy Coated Steel Sheet

    pp. 1013-1020

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    A structure of the black patina formed on the surface of 4%Al-0.1%Mg-Zn alloy coated steel during storage as a coil was investigated by various surface analyses.
    After chromating, Al-rich phase of the coating surface preferentially changed its color into black and then β-Zn phase gradually turned into the same color as Al-rich phase, which was due to the difference in growth rate of each phase. It was recognized that specific double-layered oxide film was formed on both phases : an outer layer mainly of Zn and Cr, and an inner layer mainly of Al and Zn. The black patina was related primarily to the outer amorphous oxide film which was composed with the mixture of non-stoichiometric zinc oxide and chromium oxide. The patina formation after chromate treatment was accelerated by Al and Mg in the coating. It was considered that these two elements diffused to the surface and were oxidized preferentially to form the inner layer, which accelerated the formation of non-stoichiometric zinc oxide of the outer layer.
  • Development of High Temperature Resistant Hot-dipped Aluminum Coated Steel Sheet

    pp. 1021-1028

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    A study has made of the high temperature properties of a newly developed Al-9%Si coated extra-low carbon-0.2Ti-0.6Si-1.0Mn steel sheet. Heating at high temperatures resulted in formation of diffusion layer of Al such as a cementation coatings by calorizing at the surface of the steel, because Ti in the substrate stabilizes interstitial elements which can inhibit Al to diffuse in α-Fe. Therefore the weight gain by oxidation of the steel was only about ten times that of SUS410L stainless steel sheet at 700°C and 800°C in air. It was found that the alloying behavior between coatings and substrate was caused by diffusion of Al from coatings to substrate, and diffusion depth of Al was represented as a function of temperature and time. Since the strength of the steel at high temperature up to 800°C is nearly equal to that of SUS410L, it is expected to apply the steel to automotive exhaust systems and the like in place of SUS410L.
  • Effect of Steel Composition on Heat Resistance and High Temperature Strength of Hot Dip Aluminized Steel Sheet

    pp. 1029-1036

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    In order to assure heat resistance at high temperatures and keep high temperature strength of aluminized steel sheet, the authors investigated the effect of the alloying elements added to the extremely low carbon base steel containing titanium.
    (1) Heat resistance
    Titanium and manganese have remarkable effect on decreasing the oxidation weight gain. However, silicon, phosphorus and boron weaken the oxidation resistance in such a way to increase the oxidation weight gain. Aluminium and chromium have no effect on heat resistance.
    (2) High temperature strength
    Boron is the most effective element to improve high temperature strength. Silicon, manganese and phosphorus have also favorable effect on it.
  • Organic-silicate Composite Coated Ni-Zn Plated Steel Sheet with High Corrosion Resistance for Automobile Bodies

    pp. 1038-1043

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    As zinc rich paint coated steel sheet, such as Zincrometal, affords excellent corrosion resistance even without finish painting, it is employed extensively as corrosion resistant precoated steel sheet for automobile bodies as well as zinc and zinc alloy plated sheet. However, when zinc rich paint coated steel sheet is pressformed, many problems arise. The coating film tends to peel and corrosion resistance of the formed areas deteriorates. Another problem is poor weldability.
    In order to improve these unsatisfactory performances of the product, we have developed Ni-Zn plated sheet coated with a new organic-silicate composite entirely different from zinc rich paint film.
    The new coating consists of two layers on Ni-Zn alloy plated steel sheets. The lower layer is an inorganic chromate film and the upper layer is an organic-silicate composite film of colloidal silica which is chemically combined with organic materials. The new product is superior to zinc rich paint coated steel sheets in corrosion resistance, powdering and weldability due to excellent performances of thin (about 1μm) organic-silicate composite film.
  • Effect of Paint Film Factors on Press Forming of Zinc-rich Primer Painted Steel Sheet

    pp. 1044-1050

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    A zinc-rich primer painted steel sheet for automobile body has much zinc powder in paint film for the purpose of doing spot welding. A paint film which has a large quantity of pigment is brittle and susceptible to flaking by press forming, and its corrosion resistance becomes poor. Some paint film factors influencing its flaking by press forming were studied.
    (1) By the addition of lubricant (ex. MoS2) to paint film, the flaking of the paint film is reduced. The effect of the lubricant addition is due to the reduction of the friction coefficient of paint film. As an other effect the lubricant is coated on the die, and good lubrication appears.
    (2) Generally, zinc powder content of zinc-rich primer paint film is about 90 wt%. By decreasing zinc powder content of paint film, the flaking of paint film is reduced. As the paint film becomes thicker, the shear stress on it decreases and flaking of the paint film is reduced.
    (3) The flaking of paint film on electroplated Ni-Zn alloy steel sheet is less than that on cold rolled one.
  • Effect of Paint Film Properties on the Corrosion Behavior of Pre-coated Stainless Steels

    pp. 1051-1058

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    The corrosion properties of stainless steel sheets pre-coated with many kinds of paints were examined by natural weathering test along with CASS test. The cross section of specimens exposed were studied with the microscope and the EPMA.
    (1) In the case of uncoated stainless steel, its corrosion showed narrow pits.
    (2) In the case that painted film had bad durability, corrosion of stainless steel showed wide pits under the film.
    (3) In the case that painted film had good durability but poor adhesion, corrosion of stainless steel showed wide pits like crevice corrosion.
    (4) In the case that painted film had good durability and good adhesion, no corrosion of stainless steel was found.
  • The Present Situation and Perspectives of Physical Vapor Deposition and Its Related Techniques

    pp. 1060-1069

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  • Development of Continuous Zinc Vapor Deposition Process on Steel Strips

    pp. 1070-1077

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    A new coating process in which zinc vapor is continuously deposited on steel strips in a vacuum has been developed through laboratory studies and pilot plant tests with maximum line speed 30 m/min. and maximum strip width 300 mm. The process has shown high productivity due to the high evaporation rate for plating from thin to thick coating. The method of instantaneous change of coating weight and the continuous operation have been achieved. The quality of the product made by this pilot plant is almost as good as electroplated one on coating adhesion and corrosion resistance.
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  • recoated Steel Sheets for Automotive Use

    pp. 1078-1083

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    x

    Readers Who Read This Article Also Read

    1. Alloying Behavior of Galvannealed Steel Sheets Tetsu-to-Hagané Vol.70(1984), No.14
    2. The Production Technology of High Strength Steel Sheets and Their Properties Tetsu-to-Hagané Vol.68(1982), No.9
  • Correlation between the Anti-cratering of Surface-treated Steels and the Change of Electric Currents during the Electrodeposition Coating

    pp. 1084-1089

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    The effect of the electric current density during the electrodeposition coating on the anti-cratering of surface-treated steels was studied.
    1) The electric current density during the electrodeposition coating varied with the time in the slow-start method and many current density peaks were observed. The first peak current density was named as iA, the final peak iB.
    2) The iB/iA varied discontinuously with the applied voltage and the voltage, at which the iB/iA increases discontinuously, was named the critical voltage.
    3) It was found that the critical voltage was correlated with the tendency for the cratering of surface-treated steels and the steel having the high critical voltage showed the good anti-cratering properties.
  • Corrosion Behaviour of Cold Rolled and Zinc Alloy Plated Steel Sheets in Various Kinds of Corrosion Tests

    pp. 1090-1097

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    Corrosion resistance of cold rolled, Zn-Fe and Zn-Ni alloy electrogalvanized steel sheets with and without ED-painting was investigated by means of salt dipping(DIP), saltspraying(SST) and cyclic corrosion test (CCT) including DIP, SST, drying(DRY) and humidifying(WET). From these results, the role of the unit test of CCT in corrosion behaviour of these materials was discussed.The results obtained are summarized as follows ;
    (1) In the case of unpainted specimens, SST is very aggressive environments compared with DIP. The combination of DRY or WET with DIP increased both the weight loss and the corrosion depth of the specimen. However when it was combined with SST, the weight loss increased and the corrosion depth decreased
    (2) DRY and WET in corrosion behaviour of ED-painted specimens played an inverse role in unpainted specimens. In particular, WET accelerated the paint exfoliation which affected the perforation corrosion.
    (3) Zn-Fe and Zn-Ni alloy electroplated steels showed a good corrosion resistance compared with the cold rolled steel in all kinds of tests.
  • Analysis of Perforation Corrosion of Cold Rolled and Galvanized Steel Sheets by Extreme-value Statistics

    pp. 1098-1105

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    The perforation corrosion of steel and galvanized steels due to the cyclic corrosion tests(CCT) has been analyzed by the extreme-value statistics.
    The plots of the maximum values of perforation corrosion depth and the cumulative probability gave straight lines and they were fitted to the Gumbel(Doubly exponential probability) distribution.
    The decrease of the slope of these lines with CCT time suggested that uniform corrosion occurred in an early stage of CCT but it changed to uneven corrosion with CCT time.
    The period of the uniform corrosion corresponds to the incubation time, ti of perforation corrosion and ti of the steel was extended proportionately with zinc coating weight.
    The perforation corrosion rate of Zn-Ni alloy electroplated steel after ti was lower than those of other materials. This phenomenon seems to be attributable to formation of a protective corrosion product of ZnCl2·4Zn(OH)2 and a good adhesion of the product to the steel.
  • Effect of Coating Weight on Cosmetic Corrosion Performance of Zn and Zn-alloy Electroplated Steel Sheets in Automotive Body

    pp. 1106-1110

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    Cosmetic corrosion performance of Zn-Fe, Zn-Ni alloy and Zn electroplated steel sheets was evaluated by paint creepage behavior at the scratch where both of substrate steel and the plated layer were exposed to corrosive environment.
    On the other hand, galvanic corrosion behavior of the plated layer at the scratch was investigated by electrochemical measurement.
    Since the Zn plated layer corrodes under cathodic control ; that is, corrosion current density is proportional to the ratio of exposed area of substrate steel to that of the plated layer (C/A ratio), the decreace of the value by increasing the plated coating weight retards blister formation.
    The Zn-Fe alloy plated layer corrodes by 'preferentially dissolution mechanism' when C/A ratio is rather high. In such a case, paint blister appears to be formed earlier.
    The high corrosion resistance of Zn-Ni alloy layer is effective for retarding cosmetic corrosion. The only problem, the loss of cathodic protection' ability, may be occured in the case of fairly high C/A ratio.
    In this work, the new cyclic corrosion test that mainly consists of humidity test at room temperature was devised.
  • A Study on Cosmetic and Perforation Corrosion Test for Automotive Steel Sheets

    pp. 1111-1118

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    The use of a cyclic corrosion tests, consisted of the salt spraying, wet and dry conditions, is desirable in the evaluation of the corrosion of automotive body panels in an accelerated manner.
    Defining a wet % as a percentage of a wet period in a total test time, it is required to use the wet % of below 40 for the evaluation of the cosmetic corrosion resistance. This is a reasonable requirement when the corrosion of actual automotive bodies is considered.
    In this experiment it was found that zinc coated sheets showed less blisters than cold rolled steel sheets and exhibited good cosmetic corrosion resistance at 40 wet %. When the wet % was above 70, significant blister occurred on the Zn coated sheets with the anodic Zn dissolution.
    For the perforation corrosion the percentage of the wet period should be above 50 % since the corrosion proceeds in a wet condition. It was found that the high frequencies of a wet-dry cycle was effective to accelerate the corrosion and that zinc coated steels showed good perforation corrosion resistance.
  • The Wet Adhesion of the Paint Film on Zn-Fe Electroplated Steel Sheet

    pp. 1119-1124

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    Factor controlling the wet adhesion of the paint film was investigated using various Fe content of Zn-Fe electroplated steel sheets. The wet adhesion of the paint film on Zn-Fe electroplated steel sheets with phosphate film increased with the increase of Fe content. And Zn electroplated steel sheet showed better wet adhesion than Zn-Fe electroplated steel sheets with a little content of Fe. Without phosphate film, wet adhesion of the paint film on Zn-Fe and Zn electroplated steel sheets were excellent. The structure and Fe content of phosphate film changed with Fe content of Zn-Fe electrodeposit. Fe content lower than 30% correspond to the resion of Hopeit, Zn3(PO4)2·4H2O and that higher than 60% to phosphophyllite, Zn2Fe(PO4)2·4H2 O. Fe content of phosphate film increases with the increase of Fe content of Zn-Fe electrodeposits (ED). The higher Fe content of phosphate film brings about good wet adhesion. Phosphate film changes Zn phosphate di hydrate by loosing two crystallin waters during ED coating baking process. In water immersion, they may recover the lost water. The stability of Zn phosphate di hydrate in other words, the non-recoverability, increased with the increase of Fe cotent. It is seemed that the stability of phosphate film plays the decisive role in wet adhesion. In addition to that, the difference of wet adhesion of the paint film on Zn and Zn-Fe with a little Fe content depend on disolution of phosphate film at ED coating process.
  • A Behavior of the Crystal Water of Zinc Phosphate and Its Relationship to Wet Adhesion of Paint on Electro-galvanized Steel

    pp. 1125-1132

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    A behavior of the crystal water of zinc phosphate and its relationship to wet adhesion of paint on electrogalvanized steel has been investigated. The conversion coating of Zn3(PO4)24H2O under the paint film entirely became dehydrated Zn3(PO4)22H2O by baking the film at the every content of Ni and Mn in the coating. In the case of low contents of Ni and Mn in the coating, Zn3(PO4)22H2O became rehydrated Zn3 (PO4)24H2O by immersion in water on wet adhesion test. However in the case of high contents Ni and Mn, Zn3(PO4)22H2O was not rehydrated.
    The rehydration rate decreased with increasing the contents of Ni and Mn in the coating.
    Therefore, it was found that the coating including high contents of Ni and Mn showed a very good wet adhesion. Moreover, the crystal of zinc phosphate coating including high contents of Ni and Mn was proved to be fine, dense and almost amorphous.
  • Surface Treated Steel Sheet for Containers

    pp. 1135-1141

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  • Influence of Microstructure of Passivation Film of Tinplate on Prevention of Tin Oxide Growth

    pp. 1142-1148

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    Tin oxide growth on tinplate with aging or baking has bad influence on some performances of tinplate such as lacquer adhesive property, appearance and so on. It is important to prevent the tin oxide growth with aging from a point of view of practical uses.
    The operating condition for CDC passivation treatment developed by different suppliers might vary, resulting in differences in surface characteristics and performances of the tinplate. Differences in the characteristics of passivation film among CDC passivated tinplate which were commercially manufactured by four Japanese suppliers were examined to determine the factors which affect the prevention of tin oxide growth.
    Observations of change of the surface films with aging and quantitative micro-analyses of chromium and tin in surface films using TEM-XES (combination of Transmission Electron Microscope and X-ray Energy Spectrometer) directly revealed the influence of microstructure and nature of chromium compound on the prevention of tin oxide growth.
    More amount of tin oxide grew with aging at area where there was smaller amount of chromium, especially where there was smaller amount of electrochemically determined chromium.
  • Effect of Surface Characteristics and Welding Method on Weldability of Can Materials

    pp. 1149-1156

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    An evaluation of weldability has been made on new materials used for welded cans.
    And the relation between the electric contact resistance(Rc) and, the surface characteristics of these materials has been studied.
    Furthermore the possibility of welding of tin free steel by improving the surface characteristics and the welding method has been also discussed.
    The results obtained were summarized as follows :
    (1) A lightly tin coated steel with the nickel preplated layer, when the nodular metallic tin layer was formed, had a low Rc and a good weldability.
    (2) A tin free steel, when the granular metallic chromium layer was deposited, showed the lower Rcand the better weldability than the tin free steel which has flat metallic chromium layer.
    (3) The improved welding method, which applies pre-pressing on the blank edge before seam welding or uses tin coated copper wire for intermediate electrodes, also showed lower Rc and raised weldability.
  • Coverage and Microstructure of Fe-Sn Alloy Layer on Tinplate Formed at High Temperature Region

    pp. 1157-1164

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    The morphology of Fe-Sn alloy layer on tinplate formed at temperature between 237 and 700°C was investigated. The alloy formation was carried out by the use of an infrared heating furnace which was capable of varing alloying temperature and its heating rate.
    The alloy layer formed between 400 and 550°C had granular structure and improved degree of coverage on steel surface which was remarkably different from usual alloy layer formed at normal reflowing condition (pillar structure). The morphology of alloys did not change even if the heating rate varied. It was found that the crystal structure of alloys on fully-alloyed tinplates produced during heat-treatment whose alloying temperature varied from 400 to 700°C changed in the order FeSn2→FeSn→Fe3Sn2→Fe3SnC with increasing alloying temperature. The degree of coverage of the alloy layer improved as alloying temperature was elevated.
  • Effect of Nickel Diffusion Layer on Weldability and Corrosion Resistance of Lightly Tin-coated Steel

    pp. 1165-1172

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    Lightly tin coated steels with a nickel diffusion layer on steel have been studied on corrosion resistance and weldability. The nickel diffusion layer is provided by nickel-plating and annealing processes through a continuous annealing line.
    The nickel diffusion layer plays an important role in improving corrosion resistanec by decreasing the corrosion potential difference between tin and base metal, and by forming a dense and homogeneous Fe (Ni)·Sn2 alloy layer in flow melting process.
    A convex and discontinuous structure of the metallic tin layer can be obtained by the flow melting process using a special flux. Metallic tin amount of more than 0.1 g/m2 which is necessary for high speed welding is secured after lacquer baking by the convex and discontinuous structure of the metallic tin layer.
    The nickel diffusion layer improves the corrosion resistance after lacquering. Furthermore the chromate layer consists of metallic chromium and hydrated chromium oxide improves the corrosion resistance after lacquering.
  • Behavior of Tin Electro-deposition and Spontaneous Tin Alloy Formation on Nickel Flash-coated Steel Surface

    pp. 1173-1180

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    The behavior of β-Sn electro-deposition and successive spontaneous Ni-Sn alloy formation on Ni flash-coated steel surface were studied for the development of low tin plated steel sheet for the welded can production. The results are as follows :
    1) The crystal orientation of deposited β-Sn on Ni flash-coated steel surface shows a very strong preference for β-Sn(200) plane.
    2) The Ni-Sn alloy formation occurs spontaneouly at Sn/Fe interface during the electro-deposition. After the deposition, the alloy formation proceeds during aging at room temperature and reaches a saturated amount.
    3) The chemical composition of the saturated Ni-Sn alloy shows the Sn/Ni mass ratio of 6.5.
    4) From the stoichiometric examination and the crystallographic determination it is concluded that the saturated Ni-Sn alloy is composed of Ni3Sn, Ni3Sn2 and amorphous β-Sn.
  • Influence of Reverse Electrolysis on Lacquer Adhesivity of Tin Free Steel

    pp. 1181-1188

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    The application of anodic (reverse) electrolysis to the 2 step process of tin free steel has brought the improvement of lacquer adhesivity during retort treatment. This new process consists of chromium plating, reverse electrolysis and chemical treatment.
    It was found that the reduction of anions (sulfate ions, fluoride ions) and the uniform thickness of the Cr-oxide layer of tin free steel were necessary to good lacquer adhesivity. The steel after the chromium plating has a Cr-oxide layer with a lot of anions and uneven thickness. The reverse electrolysis removes the upper anion rich part of the Cr-oxide layer. Furthermore the chemical treatment in a CrO3 bath without anion addition forms a uniform Cr-oxide layer with less anions providing good lacuer adhesivity.
  • Adhesion of Biaxially Oriented Polyethylene Terephthalate Film to Tin Free Steel

    pp. 1189-1196

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    When biaxially oriented polyethylene terephthalate (PET-BO) film was laminated on tin free steel (TFS) at 260°C (melting point of PET) or slightly higher temperatures, it began to fuse in its interfacial layer, transforming to a non-oriented and amorphous film.
    Amorphous PET layer contributed to the adhesion to TFT and the residual PET-BO layer influenced the formability and corrosion resistance. The more the residual PET-BO amount was, the better the PET film was in the water permeability resistance and the mechanical properties. On the other hand, as the residual PET-BO amount was less, the adhesion of PET film to TFS was better, being prominent when PET laminated TFS was deeply drawn into a cup.
    Thus, the adhesion and the corrosion resistance after forming changed adversely each other. However, their properties were good when the residual PET-BO amount in PET film was kept within the range of 30 to 70%. As a rapid quenching after the lamination of PET-BO film to TFS could prevent the recrystallization of the formed amorphous PET layer, the excellent adhesion of PET film to TFS was obtained.
  • Effect of Carbide Coatings by Salt Bath Immersion on Toughness of Steels

    pp. 1198-1205

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    Various steels were carbide-coated by immersing in a molten borax bath. Dynamic and static bending tests were made with these specimens in order to clarify the effects of kinds of carbide layers and substrate steels, layer thicknesses and tempering temperatures on their rupture strengths and crack formations in carbide layers.
    (1) In dynamic bending, the absorbed energy for rupture of carbide coated steels are almost the same as those of hardened steels.
    (2) In static bending, the following three cases were observed. If substrate steels were qrittle, rupture load and strain were not decreased by carbide coating, because the substrate steels ruptured at smaller load and strain than those for cracks generating in the carbide layer. If the substrate steels were tough, the rupture load and strain were not decreased, because cracks generated in the carbide layer did not induce substrate cracks. If the substrate steels had medium toughness, the rupture strength and strain decreased, because cracking in the carbide layer induced substrate cracks.
  • Effects of UV Curable Resin on the Performance of Rust Preventing Coatings for Steel Tubes

    pp. 1206-1211

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    In order to prevent temporarily the rust of steel pipe or tube, conventional rust-preventing oil such as linseed oil or synthetic alkyd resin oil diluted with appropriate organic solvents has been applied in the pipe manufacturing coating lines for many years. Because these conventional oil usually takes so long time for curing, the steel pipes and tubes coated with the oil have to be handled and transported under the uncured film conditions and easily takes damage. Because of such damage, the red rust easily comes up on the surface of steel pipe during transportation and stock in the customer's yard.
    Furthermore, oil-coating line gives rise to unpleasant and unhygienic smell for evaporated solvents in the pipe coating factory.
    Standing on this background, Ultra-violet (UV) ray curable resin coating system has been recently developed of which curing speed was under 1 or 2 s.
    In this paper, the effects of physical properties of resin polymers on the performance of UV curable coatings used in the rust preventing of the steel pipe and tube were discussed.
  • Thermal Characteristics and Long Term Durability of Polyolefine Resin for External Coating of Steel Line Pipes

    pp. 1212-1219

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    As the external coatings of steel line pipes, polyolefine resins which have exellent anti-corrosive properties are applied commonly. However, against the background of the worldwide energy crisis in recent years, the situations and the conditions associated with pipeline construction and operation tend to be increasingly severe.
    So, we have researched the thermal characteristics and the long term durability of poly-olefine resins and referred to the influences of these characteristics on the coating properties. Moreover, in order to estimate the high temperature life of polypropyrene coating, a new accelerated test method of heat deterioration which is different from the extrapolation of the oxidative induction time is tried to be established.
    The following results were obtained :
    As for the polyethylene coating, a medium density polyethylene shows the best characteristics at the temperature between -45°C and 80°C.
    As for the polypropyrene coating, a new type of the block-copolymerized polypropylene shows the exellent mechanical strength at the temperature between -30°C and 110°C.
    The long term durability at high temperature is enable to be solved by the addition (>2.4%) of specific anti-oxidants, which are sulfide and phenol compounds.

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