Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson's Solution

Abstract

Abstract: Intergranular stress corrosion cracking (ISCC) of α-brass in neutral Mattsson's solution was found to be controlled by an unusual "W"-shaped galvanic cell whose cathode is the grain boundary oxide film (G.B.0. film) and surface film and the anode is fresh metal at the cracked tip on both sides of the G.B.0. film. Redox reactions involved in the cell have been proposed here. According to this mdel, initidtion of ISCC is caused by the rupturing of surface film along grain boundaries, thus forming a galvanic cell. Propagation of ISCC resulted from alternate advances of G.B.0. film and dissolution on both sides of G.B.0. film caused by the effect of electrochemical reaction. This work developed an effective approach to investigate the embrittlement process at the tip of the crack, by increasing the length of the embrittlement region through constant strain test and distinguishing the morphology and the nature of the corrosion products by optical microscopy and scanning electron microscopy (SEH).

Key words: α-brass, intergranular stress corrosion cracking, W-shaped cell model, grain boundary oxide film

WU Shaobin;R. J. Arsenault;I. R. Kramer Metallurgical Materials Laboratory, University of Maryland, USA.. Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson's Solution[J]. J Mater Sci Technol, 1989, 5(2): 101-112.

References

[1] E.H.Dix, Jr.:Trans.AIME. 1940, 137, 11．
[2] E.H.Dix, Jr.:Proc.ASTM, 1941, 41, 928．
[3] M.Pourbaix:Thermodynamics of Dilute Aqueous Solutions, with Application to Electrochemistry and Corrosion, Thesis. 1945, Delft; 1949, Arnold, London(Translated from French by J. N. Agar).
[4] M.Pourbaix:Lectures on Electrochemica1 Corrosion, 1973, New York Plenum Press.
[5] L.Graf: in Stress Corrosion Cracking and Embrittlement(Ed. W. D. Robertson) 1956, 48,New York,John Wiley and Sons. Inc.
[6] H.Leidheiser, Jr., and R. Kissinger: Corrosion, 1972, 28, 218．
[7] H.W.Polan, J.M.Popplewell and M.J. Pryor: J. Electrochem. Soc., 1971, 7, 1299．
[8] H.W.Pickering and P.J.Byrne:J.Electrochem. Soc., 1969, 11, 1492．
[9] R.H.Heidersbach, Jr. and E.D.Verink, Jr.: Corrosion, 1972, 28, 397．
[10] R.Natarajan et al.: Corrosion, 1975, 31, 302．
[11] E.Mattsson:Electrochemica Acta, 1961, 3, 279．
[12] P.R.Swann and J.Nutting: J. Inst. Hetals, 1959--60, 88, 478．
[13] P.R.Swann and J.Nutting: J. Inst. Metals, 1961--62, 90, 133．
[14] P.R.Swann:Corrosion. 1963, 19, 102t.
[15] D.Tromans and J. Nutting: Corrosion, 1965, 21, 143．
[16] D.Tromans, N.A. Dowdes and J.Leja; in Fundamental Aspects of Stress Corrosion Cracking, (Ed. R. W. Staehle et al.), 1967, 154, Houston, National Association of Corrosion Engineers.
[17] E. N. Pugh and A. J. Sedriks: Surface and Interfaces Ⅱ, Physical Mechanical Properties, 1968, Syracuse, NY, Syracuse University Press.
[18] H. L. Logan: J. Res. Nat. Bur. Std., 1952, 48, 99．
[19] A. J. Forty and P. Humble: Philos. Mag., 1963, 8, 247．
[20] A. J. Forty and P. Humble: in Environment-sensitive Mechanical Behavior (Ed. A. R. C. Westwood and N. S. Stoloff) 403, 1966, New York, Gordon and Breach Science Publishers.
[21] J. R. Pinchback, S. P. Clough and L. A. Heldt: Metall. Trans., 1975, 6A, 1479．
[22] E. Wendler-Kalsch: in Mechanisms of Environment-sensitive Cracking of Materials(Ed. P. R. Swann et al.), 1979, 192, London, the Metals Society.
[23] ASTM Designation, G 37--73: in Annual Book of ASTM Stand., Vol. 03． 02, 1984, 285, PA, ASTM.
[24] A. V. DeForest: Proc. ASTM, 1918, 18, 205．
[25] K. H. Thompson and A. W. Trace: Metals Trans., 1949, 100．
[26] T. P. Hoar: Corrosion, 1963, 10, 331t.
[27] J. A. S. Green, H. K. Mengelberg and H. T. Yolken: Electrochem. Science, 1970, 117, 433．
[28] S. B. Wu: Dissertation, 1986, 11, University of Maryland.
[29] H. L. Logan: The Stress Corrosion of Metals, 1966, 156, N. Y. John Wiley and Sons Inc.
[30] M. F. Ashby: in Advances in Research of the Strength and Fracture of Materials, (Ed. D.M.R.Taplin), 1--5, 1977, New York, Pergamon Press Inc.
[31] A. J. McEvily, Jr. and A. P. Bond: J. Electrochem. Soc., 1965, 112, 131．
[32] H. H. Uhlig: in Stress Corrosion Cracking and Hydrogen Embrittle ment of Iron Base Alloys, (Ed.R.W. Staehle et al.) 1973, 174, Houston, National Association of Corrosion Engineers.
[33] D. A. Vermilyea and General Electric: in Fundamental Aspects of Stress Corrosion Cracking, (Ed. R. W. Staehle et al.), 1967, 15, Houston, National Association of Corrosion Engineers.