LOCALIZED ELECTROCHEMICAL CHARACTERIZATION OF HIGH STRENGTH ALUMINIUM ALLOY AT THE CRACK TIP IN 3.5NaCl SOLUTION
SHENG Hai, DONG Chaofang, XIAO Kui, LI Xiaogang
Key Laboratory of Corrosion and Protection, Ministry of Education, Corrosion and Protection Center, University of Science and Technology Beijing, Beijing 100083
Cite this article:
SHENG Hai, DONG Chaofang, XIAO Kui, LI Xiaogang. LOCALIZED ELECTROCHEMICAL CHARACTERIZATION OF HIGH STRENGTH ALUMINIUM ALLOY AT THE CRACK TIP IN 3.5NaCl SOLUTION. Acta Metall Sin, 2012, 48(4): 414-419.
Abstract The electrochemical microcapillary technique and scanning Kelvin probe (SKP) were applied to study the localized electrochemical characterization and corrosion behavior at the crack tip of 2024-T351 aluminium alloy in 3.5NaCl. To investigate the effect of stress on the localized corrosion process at the crack tip, numerical simulation of the stress distribution on a pre-cracked wedge-open loading (WOL) specimen was conducted using a commercial software package ABAQUS 6.10. Polarization curves revealed that corrosion potential at the crack tip was more negative than that within the region away from the crack tip. Localized electrochemical impedance spectroscope (EIS) showed that the passive film was thinner at the crack tip than within the region away from the crack tip. The results indicate that the crack tip is more electrochemically active than the region away from the crack tip. Furthermore, passive film at the crack tip was less stable than that on other region of the specimen surface. SKP measurements demonstrated that there was a non-uniform distribution of Volta potential on the pre-cracked WOL specimen surface, with a more positive Volta potential occurring at the crack tip after 24 h immersion into 3.5NaCl solution. This might be explained by the preferential anodic dissolution and the accumulation of the corrosion product at the crack tip. Numerical simulation results showed that a very high local stress concentration was developed at the crack tip, which could enhance the electrochemical activity around the crack tip and promote the dissolution process therein. Moreover, a galvanic couple could also occur between the crack tip acting as the anode and the distant region as the cathode, which results from the differences of the corrosion potentials and the electrochemical activities between them. As a result, the anodic dissolution of 2024-T351 aluminium alloy at the crack tip is enhanced.
LI Xiaodong; WANG Yanbin;CHU Wuyang (University of Science and TechnologyBeijing; Beijing 100083); TIAN Fang; WANG Chen; BAI Chunli (Institute Of Chemistry; Chinese Academy of Sciences; Beijing 100080). INVESTIGATION OF LOADED CRACK TIP ON MICA SURFACE BY ATOMIC FORCE MICROSCOPY[J]. 金属学报, 1997, 33(6): 588-594.
[4]
P. B. Hirsch FRS(Department of Materials; University of Oxford; Parks Road; Oxford OX1 3 PH; UK Manuscript received ). MODELLING THE BRITTLE-DUCTILE TRANSITION[J]. 金属学报, 1997, 33(3): 225-232.
[5]
ZHENG Yesha; WANG Zhongguang; AI Suhua (State Key Laboratory of Fatigue and Fracture for Materials; Institute of Metal Research; Chinese Academy of Sciences; Shenyang 110015). DISLOCATION STRUCTURE OF FATIGUE CRACK TIP[J]. 金属学报, 1995, 31(3): 105-114.
ZHOU Xiangyang;LI Jin;LIU Guanglei;KE Wei Corrosion Science Laboratory; Academia Sinica; Institute of Corrosion and Protection of Metals; Academic Sinica; ShenyangWEI Xuejun;Institute of Corrosion and Protection of Metals Academia Sinica Shenyang110015. AN APPLICATION OF SPI TECHNIQUE FOR STUDING STRAIN DISTRIBUTION AT CF CRACK TIP[J]. 金属学报, 1993, 29(6): 77-81.
LI Qingsheng (Chingshen Li);T. BRETHEAU Taiyuan University of Technology University Paris Nord Department of Mathematics and Mechanics;Taiyuan University of Technology; Taiyuan 030024. EFFECT OF GRAIN BOUNDARY ON FATIGUE BEHAVIOUR OF Al BICRYSTALS[J]. 金属学报, 1990, 26(3): 55-60.
