ORALS

SESSION: CorrosionTuePM1-R7	Macdonald International Symposium (Intl Sympos. on Corrosion for Sustainable Development)
Tue. 29 Nov. 2022 / Room: Andaman 2
Session Chairs: Junhua Dong; Session Monitor: TBA

14:25: [CorrosionTuePM106] OS
Galvanic corrosion mechanism of cn Al–BN cbradable ceal coating cystem in chloride colution
Bing Lei¹ ; Guozhe Meng² ; Ying Li³ ; Fuhui Wang⁴ ; ¹School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai, China; ²School of Chemical Engineering and Technology, Sun Yat-sen University, zhuhai, China; ³Institute of Metal Research,Chinese Academy of Sciences, Shenyang, China; ⁴Northeastern University, Shenyang, China;
Paper Id: 220 [Abstract]

In this study[1], we investigated the galvanic corrosion performance of an Aluminum–Boron Nitride (Al–BN) abradable seal coating system (with a Ni5Al bond layer and a 0Cr17Ni4Cu4Nb substrate) in chloride solution by electrochemical methods. Galvanic interaction of the coating system during corrosion has been confirmed, while the Al–BN layer assumes anodic character, while the bond NiAl and substrate act as cathodes. Negative difference effect (NDE)[2] was tested during the anodic dissolution of Al-BN top layer, which indicated that about 13% of the anodic current of the Al–BN layer was compensated by hydrogen evolution by NDE. In addition, a three-stage process occurred during the anodic dissolution of the coupled coating system, consisting of a spontaneous pitting stage I under charge transfer control with a decreasing rate, a corrosion developing stage ІІ under mass transfer control with an increasing rate, and a final steady stage III. Precipitation of Al(OH)3 restricts[3] the oxygen transport process to the cathode and induces localized acidification of the occluded pores of the Al–BN layer, which was the mechanism that could explain the changes of corrosion performance during the three immersion stages of Al–BN coating system. The study suggests that galvanic corrosion of the porous multi-layer Al–BN abradable coating system is mostly influenced by its corrosion product deposition.

References:
[1]Lei, B.; Li, M.; Zhao, Z.; Wang, L.; Li, Y.; Wang, F. Corrosion mechanism of an Al–BN abradable seal coating system in chloride solution. Corros. Sci. 2014, 79, 198–205
[2]Yu, Y.; Li, Y. New insight into the negative difference effect in aluminium corrosion using in-situ electrochemical ICP-OES.Corros. Sci. 2020, 168, 108568
[3] Håkansson, E.; Hoffman, J.; Predecki, P.; Kumosa, M. The role of corrosion product deposition in galvanic corrosion of aluminum/carbon systems. Corros. Sci. 2017, 114, 10–16.