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Abstract Constant load and potentiostatic techniques were used to study the susceptibility of SCC for H62 brass in 0.1N NH_4OH+0.1g Cu~(2+)/L solution at 30℃. It was found that a critical potential existed in this system, being about —620mV(SCE), below which the SCC would not occur. Above the critical potential, the cracks propagating along the β′ phase which dissolved prior to α phase were observed with SEM and metalloscope, and the most sensitive potential for cracking was about —200mV (SCE). Also, the simulated occluded corrosion cell designed previously by the authors was modified and used to investigate the chemical changes within S. C. cracks of this system. As anodic currents passed the cell, the pH value of occluded cell (0C) solution dropped down from about 11 to 6. 2 or less, the Zn contents of the 0C solutions increased rapidly with time, and the Cu/Zn ratio on the surface of occluded specimens increased. These facts indicate that acidification within cracks existed and dezincification occurred at the crack tips for this system.
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Received: 25 June 1992
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Cite this article:
Jin Zhiqiang; Liu Youping and Zuo Jingyi (Beijing Institute of Chemical Technology). INVESTIGATION OF CRITICAL POTENTIAL OF SCC AND CHEMICAL STATES WITHIN CRACKS FOR BRASS IN AMMONIA SOLUTION. J Chin Soc Corr Pro, 1992, 12(3): 269-274.
URL:
https://www.jcscp.org/EN/ OR https://www.jcscp.org/EN/Y1992/V12/I3/269
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