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61 NACE INTERNATIONAL: VOL. 56, NO. 11 MATERIALS PERFORMANCE NOVEMBER 2017 MP Buyers Guide Online The MP Buyers Guide is an exclusive directory of manufacturers, suppliers, and consultants worldwide that provide products and services for the prevention and control of corrosion. To access the online version of the MP Buyers Guide, as well as add or edit your company's listing, please go to www.mpbuyersguide.com. r o s i o n C D ( I c o r r ) a n d c o r r o s i o n ra t e increased. More-negative corrosion poten- tials corresponded to greater electrochemi- cal activity as the alloy became more sensi- tive to corrosion and displayed reduced corrosion resistance. The relationship between the corro- sion rate and hydrogen concentration is presented in Figure 3, which shows that the corrosion rates of the alloys increased with increasing hydrogen concentration. This result suggests that hydrogen pro- moted corrosion in the aluminum alloy because hydrogen was introduced into the aluminum alloy by electrolytic cathodic hydrogen charging, and the hydrogen con- c e n t ra t i o n i n c re a s e d w i t h i n c re a si n g hydrogen charging time (Figure 1). Hydro- gen segregation o c curred at th e grain boundar y, enlarging th e cr ystal lattice constant while reducing the average bond- ing energy and interatomic bonding force of the grain boundary atoms. This led to a grain boundar y weakness and increased susceptibility to HE. 13 Therefore, the alu- minum alloy became more sensitive to corrosion. The aging condition also had an influ- ence on the corrosion resistance of 7050 aluminum alloy. Under the same charging conditions, the corrosion resistance of the alloy in the underaged state was the worst, the alloy in the over-aged state proved to have the best corrosion resistance, and the peak-aged alloy was in the middle of the other two. Conclusions 1. Hydrogen concentration increased with increasing hydrogen charging time within the same aging state. 2. Under the same aging conditions, the free corrosion potential (E corr vs. SCE) becam e less electron egative with increasing hydrogen charging time while the corrosion CD (I corr ) and cor- rosion rate increased. With increas- ing hydrogen charging time, more- n e g a t i v e c o r r o s i o n p o t e n t i a l s c orresp ond ed to great er el e ctro- chemical activity, greater sensitivity to corrosion , and reduced corro- sion resistance. Acknowledgments Financial aid from the National Natural Science Foundation of China under grant no. 51371039 and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) are grate- fully acknowledged. References 1 N.J.H. Holoroyd, G.M. Scamans, "Stress Cor- rosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environment," Metall. Mater. Trans. A 44 (2013): pp. 1,230-1,253. 2 G. Silva, et al., "Study of the SCC Behavior of 7075 Aluminum Alloy After One-Step Aging at 163 °C," J. Mater. Eng. Perform. 22 (2013): pp. 210-214. 3 D. Najjar, T. Magnin, T.J. Warner, "Influence of Critical Surface Defects and Localized Competition Between Anodic Dissolution and Hydrogen Effects During Stress Corro- sion Cracking of a 7050 Aluminum Alloy," Mater. Sci. Eng. A 238 (1997): pp. 293-302. 4 S. Osaki, H. Kondo, K. Kinoshita, "Contribu- tion of Hydrogen Embrittlement to SCC Pro- cess in Excess Si Type Al-Mg-Si Alloys," Mater. Trans. 47 (2006): pp. 1,127-1,134. 5 N. Takano, "Hydrogen Diffusion and Embrit- tlement in 7050 Aluminum Alloy," Mater. Sci. Eng. A 483-484 (2008): pp. 336-339. 6 H.K. Birnbaum, "Hydrogen Effects on Defor- mation and Fracture: Science and Sociology," MRS Bull. 28 (2003): pp. 479-485. 7 G.M. Pressouyre, "Trap Theory of Hydrogen Embrittlement," Acta Metall . 28 (1980): pp. 895-911. 8 W.Y. Chu, L.J. Qiao, Fracture and Environmen- tal Fracture (Beijing, China: Science Press, 2000). 9 G.M. Scamans, N.J.H. Holroyd, C.D.S. Tuck, "The Role of Magnesium Segregation in the Intergranular Stress Corrosion Cracking of Aluminium Alloy," Corros. Sci. 27 (1987): pp. 329-347. 10 R .K. Viswanadhan, T.S. Sun, J.A.S. Green, "Grain-Boundary Segregation in Al-Zn-Mg Alloys—Implications to Stress-Corrosion Cracking," Metall. Trans. A 11 (1980): pp. 85- 89. 11 G.M. Bond, I.M. Robertson, H.K. Birnbaum, "Effects of Hydrogen on Deformation and Fracture Processes in High-Purity Alumi- num," Acta Metall. 36 (1998): pp. 2,193-2,197. 12 W.Y. Chu, et al., "Effect of Hydrogen on Stress Induced by Dezincification Layer on Brass," J. Nonferrous. Met. 12 (2002): pp. 625-628. 13 W.J. Qi, et al., "Hydrogen Embrittlement Sus- ceptibility and Hydrogen-Induced Additive Stress of 7050 Aluminum Alloy Under Vari- ous Aging States," J. Mater. Eng. Perform. 24 (2015): pp. 3,343-3,355. 14 R .G. Song, et al., "Grain Boundary Segrega- tion and Hydrogen-Induced Fracture in 7050 Aluminium Alloy," Acta Mater. 44 (1996): pp. 3,241-3,248. 15 R.G. Song, et al., "Stress Corrosion Cracking and Hydrogen Embrittlement of an Al-Zn- Mg-Cu Alloy," Acta Mater. 52 (2004): pp. 4,727- 4,743. W.J. QI is a researcher at Jiangsu Key Laboratory of Materials Surface Science and Technology, Changzhou University, Changzhou, Jiangsu Province, China, email: 948723442@qq.com. Her research interests focus on corrosion and protection of metallic materials. X. QI is a researcher at Jiangsu Key Laboratory of Materials Surface Science and Technology. B. SUN is a researcher at Jiangsu Key Laboratory of Materials Surface Science and Technology. C. WANG is a researcher at Jiangsu Key Laboratory of Materials Surface Science and Technology. J.R. JIN is a researcher at Jiangsu Key Laboratory of Materials Surface Science and Technology. R.G. SONG is a professor at Jiangsu Key Laboratory of Materials Surface Science and Technology, email: songrg@hotmail. com. His research interests focus on stress corrosion cracking, hydrogen embrittle- ment, and surface modification. He has authored several journal articles. Study on Electrochemical Corrosion of 7050 Aluminum Alloy