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    Apr. 1991, Volume 11 Issue 2 Previous Issue    Next Issue
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    THE APPLICATION OF KRAMERS-KRONIG TRANSFORMS IN IMPEDANCE DATA ANALYSIS Ⅰ. THE RELATION BETWEEN KRAMERS-KRONIG TRANSFORMS AND STABILITY ANALYSIS OF FARADAIC ADMITTANCE
    Zhang Jianqing Cao Chunan (Corrosion Science Laboratory; Institute of Corrosion and Protection of Metals; Academia Sinica)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 105-110. 
    Abstract   PDF (467KB) ( 964 )
    The following two Faradaic admittance equations (1) and (2), the derivation of which is based on the stability conditions of steady state are examined by Kramers-Kronig transforms. Y_F=1/R_t+B/(a+jω) (1) Y_F=1/R_t+(A+jBω)/(D-ω~2+jωT) (2) The conditions required by stability,a>0 for equation(1)and T~2≥4D,D>0 for equation (2), must also be satisfied in Kramers-Kronig transforms. The applications of the two equations in impedance data analysis are briefly discussed.
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    THE APPLICATION OF KRAMERS-KRONIG TRANSFORMS IN IMPEDANCE DATA ANALYSIS Ⅱ. ANALYSIS FOR VALIDATION OF IMPEDANCE DATA
    Zhang Jianqing Cao Chunan (Corrosion Science Laboratory;Institute of Corrosion and Protection of Metals;Academia Sinica)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 111-118. 
    Abstract   PDF (517KB) ( 945 )
    A method used to check the reliability of impedance data by Kramers-Kronig transforms has been developed. The procedure consists of first,to fit experimental impedance data to the impedance expressions having true physical meaning and then,to extrapolate the fitting results to whole frequency range. In this way some errors in integral calculation can be avoided and the validity of the method can be improved. A fitting program which deals with the impedance spectra with three time constants has been proposed.
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    OXIDATION BEHAVIOUR OF A COMPOSITE NiAl-TYPE COATING CONTAINING La_2O_3 ON Ni-BASE SUPERALLOY
    Li Tiefan Ma Xinqing (Institute of Corrosion and Protection of Metals;Corrosion Science Laboratory; Academia Sinica)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 119-124. 
    Abstract   PDF (1982KB) ( 828 )
    A composite NiAl-type coating containing La_2O_3 was prepared by composite electrodeposition with subsequent aluminizing. The oxidation behaviour of such a coating at 1100℃ was studied. The oxidation kinetics of the coatings and the morphology of the scale indicated that,the oxidation rates of the coatings were reduced greatly and the spallation resistance of the scale was improved markedly because the additive La_2O_3 improved the quality and adherence of the scale effectively. The results of EPM analysis showed that,the dispersing of La_2O_3 in Ni-La_2O_3 layer accumulated and formed a La_2O_3-rich layer in the vicinity of the coating/substrate interface just after aluminizing, which could inhibit the degradation of the coatings oxidized. In the meantime, the mechanism by which La_2O_3 increased the oxidation resistance of the coationgs was discussed.
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    A STUDY ON THE ANODICALLY PASSIVATED FILM OF SUS36 STAINLESS STEEL
    Chen Zhuqiu Xu Chuanpi Huang Nishang Shi Xiaoyan Hu Shifu (Xiamen Corrosion and Protection Branch;Fujian Institute of Research on the Structure of Matter; Academia Sinica) Zhang Yongfu (Institute of Shanghai Petro-Chemical Complex)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 125-131. 
    Abstract   PDF (571KB) ( 809 )
    The relationship between physicochemical features of passive film and the corrosion resistance of SUS36 stainless steel has been studied by electrochemical methods,such as potentiostatic polarization, potential decline, alternating current impedance and XPS surface analysis. The corrosion resistance of the passive film formed in transpassive region is better than that in passive region.
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    A COMPARISON OF INHIBITION MECHANISM OF ZINC PHOSPHATE IN AQUEOUS SOLUTION AND IN ALKYD COATNG
    Su Fangteng Wen Guomou Liu Bihuan Cai Changshou Guo Jingdong (Fujian Institute of Research on the Structure of Matter; Academia Sinica)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 132-138. 
    Abstract   PDF (523KB) ( 1046 )
    The difference of inhibition mechanism of zinc phosphate in aqueous solution and in alkyd coating has been studied by using electrochemical techniques. Zinc phosphate is hardly inhibitive to bare steel in neutral solution containing chloride ions,but it behaves as an outstanding inhibitive pigment in alkyd coating. The reasons for the high inhibiting effect in the coating may be as follows: (a)zinc phosphate increases the resistance of the coating to the permeation of water and to the diffusion of oxygen or other corrosive ions through the paint film; (b)during the operation of the differential aeration cell beneath the coating,zinc phosphate imparts excellent buffering action to the anolyte and catholyte and acts as an effective inhibitor to the base metal, consequently the blistering tendency of the paint film at the cathode and the corrosion rate of base metal at the anode are lowered.
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    DESIGNING A CORROSION DATABASE
    Li Changrong (University of Science and Technology; Beijing) David B. Anderson (U. S. National Institute of Standards and Technology)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 139-144. 
    Abstract   PDF (485KB) ( 884 )
    Designing a corrosion database needs to give comprehensive considerations to not only the data inputs to represent the overall conditions,but also the users' conveniences to input,output and access corrosion data,so that the application and consultation programs can be developed flexibly. A prototype of database program for corrosion of materials in industrial environments has been developed. The data structure of the corrosion database and the design method of the application program are introduced in this prper. The standardized data formats of the Corrosion Data center established by National Association of Corrosion Engineers (NACE)and National Institute of Standards and Technology (NIST) are adopted. The program permits easy data input,output,modification,addition,deletion and data selection. In addition, users can retrieve and access the corrosion data according to different purposes.
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    GAS CORROSIVITY SENSORS IN TYPE OF MULTI-HOLED PLANAR CELL
    Weng Yongji Li Xiangyi (Research Institute;Hua-Dong Pipeline Bureau)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 145-152. 
    Abstract   PDF (597KB) ( 844 )
    An electrochemical monitoring cell consisting of two multi-holed plates sandwiched by a dielectric foil has been developed as corrosion sensors in the authors' lab. Based on the cell current and its accumulated quantity the mean or instantaneous corrosion rates of metals in gases can be measured and recorded continuously. In this paper the construction and characteristics of the sensors are described. For the carbon steel sensor in electrolytic cell,the quantitative relation between cell current and true weightloss defined as the cell's factor was studied. In addition,some applications of above sensors were illustrated and the results of on-line monitoring tests of corrosion in atmospheres or in industrial exhaust gases or inside natural gas pipeline were reported respectively.
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    CASE HISTORY OF HIGH TEMPERATURE SULPHUR CORROSION IN OIL REFINERY
    Wang Maocai Wu Weitao (Corrosion Science Laboratory; Institute of Corrosion and Protection of Metals; Academia Sinica) Zhang Qi (Jingmen oil Refinery;Jingmen;China)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 153-162. 
    Abstract   PDF (4243KB) ( 897 )
    Three high temperature sulphur corrosion cases have been studied. They are: the corrosion failures of a hydrogen-generated furnace tube(HK40 type steel) and its weld metal (Ni based alloy) for naphtha steam reformer serviced in combustion gases atmosphere at 800~950℃for more than 15,000 hrs and a pulling rod (20CrMo steel)for reflector plate in a U-shape heat exchanger of a hydrogen refining unit operated in H_2/H_2S gas mixture at about 420℃ for more than one yrar. The corrosion morphology,microstructure and chemical composition of the corrosion products were examined by means of optical microscopy,XRD,SEM,EPMA and IPMA. The results were discussed in term of thermodynamic stability diagram to reveal the nature of the corrosion process. A synthesis action mode was proposed to illuctrate the formation mechanism of the multilayered scale of ferrous sulfide on low alloy steel pulling rod.
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    HYDROGEN ASSISTED CRACKING OF 30CrMnSiA STEEL UNDER CONTINUOUSLY HYDROGEN CHARGING AND (Ⅰ+Ⅱ) MIXED MODE LOADING CONDITION
    Gao Hua Cao Weijie (Shanghai University of Engineering Science)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 163-168. 
    Abstract   PDF (356KB) ( 812 )
    Hydrogen assisted cracking (HAC) of 0. 3%C, 1%Cr, 1%Mn, 1%Si steel under continuously hydrogen charging and (Ⅰ+Ⅱ) mixed mode loading conditions was studied. Experimental results showed that under mixed mode loading conditions from mode I through mode Ⅱ ,the critical stress intensity factor K_H for HAC increased firstly and then decreased,thus at some K_Ⅱ/K_Ⅰ ratio K_(Hmax) occurred. In both mode Ⅰ and mode Ⅱ cases, however,K_(ⅠH) and K_(ⅡH) were rather low,and sometimes K_(ⅡH) was even lower than K_(ⅠH).
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    THE CORROSION RESISTANCE OF ELECTROLESS Ni DOUBLE-LAYER DEPOSIT
    Lu Zhu Zhang Gang (East China University of Chemical Technology)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 169-174. 
    Abstract   PDF (628KB) ( 909 )
    The corrosion resistance and anti-corrosion mechanism of the double-layer electroless Nickel alloy deposit system, Ni-P (7. 5μm, outer)+Ni-Mo-P(2. 5μm, inner), were studied. The results of immersion corrosion test and neutral salt spray test showed that in so far as corrosion resistance is concerned, the double-layer deposit was much better than the single-layer (Ni-P or Ni-Mo-P) deposits of the same thickness and that it was better than the single-layer deposit of twice the total thickness. After heat treatment above 400℃, the corrosion resistance is further improved. AES surface analysis and depth profile technique,x-ray diffraction analysis technique,electrochemical tests and metallographic techniques were employed to investigate the anti-corrosion mechanism of this system. The results showed that the outer layer served as a sacrificial anode to provide electrochemical protection to the inner layer when the double-layer deposit was heat treated below 400℃ (including untreated condition),and that the protective effects were due to the changes of structure of system and had higher anti-corrosion performance when heat treated above 400℃.
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    FATTY SALTS AS INHIBITORS AND THEIR INHIBITION MECHANISM
    Zhou Derui Li Xuegang~* Jiang Zhaohua Shao Guangjie~(**) and Li Jianqiang (Harbin Institute of Technology) * Post doctor of lnstituts of Biophysics of the Academia Sinica ** Yanshan University
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 175-180. 
    Abstract   PDF (440KB) ( 794 )
    Inhibition capability of fatty acids for protection of carbon steel was evaluated by AC impedance and potentiodynamic measurenents. Logarithmic relation was obtained between polarization resistance R_p and concentration of linoleic acid C_L:R_P=A+BlgC_L. The excellent inhibition capability of linoleic salts could be attributed to the following factors; (1)their easy adsorption on metallic surface raises the activation energy of corrosion reaction; (2)multi-layer adsorption film further strengthens isolation of metal from corrosive medium; (3)the longer the carbon chain of fatty acid,the more effective their adsorption capability. Experimental results show that the inhibition effect of fatty salts against corrosion of carbon steel is based on the depression of electrode processes, predominantly the anodic process.
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    EFFECT OF ALUMINIZING ON THE HOT CORROSION RESISTANCE OF THE SPUTTERED CoCrAlY COATING
    Lou Hanyi Wang Fuhui Bai Linxiang (Institute of Corrosion and Protection of Metals; Academia Sinica)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 181-187. 
    Abstract   PDF (3117KB) ( 779 )
    The hot corrosion behaviour of Co-30Cr-6Al-0. 5Y coating produced by magnetron sputtering deposition and that of the said coating with subsequent aluminizing have been investigated in sulphate melt,but its hot corrosion resistance in molten salts. The results show that the CoCrAlY coating possesses excellent hot corrosion resistance in sulphate melt,but its hot corrosion resistance in molten salts containing NaCl is reduced severely after 100 hrs. With subsequent aluminizing of the CoCrAlY coating its resistance to hot corrosion is only slightly reduced in sulphates melt and is remarkably improved in salt melt containing NaCl. The different influence factors of aluminizing on the hot corrosion resistance of the CoCrAlY coatings in various salt melts have been discussed.
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    CORROSION BEHAVIOUR OF SOME IRON, AND NICKEL-BASED ALLOYS IN MIXED SALTS OF 25Na_2SO_4-75K_2SO_4(wt%) AT 900℃
    Guo Manjiu Lu Yaxuan (Beijing Central Research Institute of Iron and Steel) Zhu Rizhang Zheng Xiaoguang (The University of Science and Technology; Beijing)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 188-192. 
    Abstract   PDF (1668KB) ( 776 )
    Specimens of three chromia-forming alloys,Fe-25Cr-2Mo,Fe-25Cr-20Ni,Ni-28Cr-2Cu-RE,and of two alumina-forming alloys, Fe-25Cr-6Al-0. 4Y, Fe-40Ni-21Cr-6Al-0. 1 Y,were exposed to the ambient atmosphere at 900℃ in the mixed salts of 25Na_2 SO_4-75K_2SO_4 (wt. %). Corrosion products were analysed by X-ray diffraction and electron microscopy. Sulfate salts tagged with. ~(35)S were used; sulfur penetration profiles were then determined,and the lateral distribution of sulfur within the alloy matrix was observed by autoradiography. Internal sulfidation/internal oxidation was found to be the major mode of attack, preferably along grain boundaries. The chromia scale was rather thick, permitted rapid inward penetration of sulfur to form chromium sulfide along the grain boundaries. Alumina scale offered better protection than did chromia scale. By comparison, the two alumina-forming alloys were found to be more resistant than the other three chromiaforming alloys under the experimental conditions.
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    THE EFFECT OF NITROGEN IMPLANTATION ON CORROSION RESISTANCE OF 1Cr18Ni9Ti
    Weng Duan Gao Wanfu Huo Shizhong (Dalian University of Technology)
    Journal of Chinese Society for Corrosion and protection, 1991, 11 (2): 193-196. 
    Abstract   PDF (538KB) ( 748 )
    The modification of corrosion resistance of 1Cr18Ni9Ti stainless steel in Phosphonitrogen by nitrogen implantation was investigated by electrochemical measurements, TEM and AES. The results show that the open potential of implanted specimens shifts towards positive direction and that their corrosion current measured by weak polarization technique decreases. The passive current density is greatly affeted by implantation dose. The best modification effect has been obtained at dosage of 1×10~(17) N~+/cm~2 when an amorphous structure of the formation of nitride precipitate,excessive implantation is detrimental to corrosion resistance of the stainless steel.
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