Corrosion Behavior of Brass H62 in Harsh Marine Atmosphere in Nansha Islands, China
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Corrosion Behavior of Brass H62 in Harsh Marine Atmosphere in Nansha Islands, China Xiao Lu
, Yuwei Liu, Hongtao Zhao, and Zhenyao Wang
(Submitted June 2, 2020; in revised form October 10, 2020; Accepted October 26, 2020; published online 10 November 2020) The corrosion behavior of brass H62 exposed to the atmosphere of Nansha Islands for 21 months was investigated by weight loss, scanning electron microscopy, x-ray diffraction and electrochemical techniques. The results showed that the average corrosion rate of brass H62 exposed for 1 year was approximately 13.47 g m−2 a−1, and the corrosion products were observed to be unevenly distributed, attributed to the dezincification corrosion. In addition to the zinc-containing compounds Zn5(OH)8Cl2·H2O and NaZn4(SO4) Cl(OH)6·6H2O, the copper-containing compounds Cu2O and Cu2Cl(OH)3 were also detected on the front side of the exposed sample, while only the zinc-containing compounds were detected on the back side. Both sides of brass H62 showed a decreasing corrosion rate, but the corrosion product layer on the back side appeared to be more protective for the same exposure time.
Keywords
atmospheric corrosion, brass, composition analysis, electrochemical technology, weight loss
1. Introduction Brass is widely used in electronic and electrical, machinery manufacturing, national defense industry and other fields due to its superior electrical and thermal conductivities, good corrosion resistance and desirable hardness and strength compared to pure copper (Ref 1). Nevertheless, brass is susceptible to appreciable atmospheric corrosion when exposed to the environments containing corrosive media (such as SO2, H2S, NO2 and Cl−). Similar to other metal materials, its atmospheric corrosion is a complex physical and chemical process, essentially an electrochemical reaction under a thin liquid film (Ref 2), which is mainly affected by environmental parameters such as temperature, relative humidity and atmospheric pollutants. To this end, a series of studies have been conducted on the corrosion mechanism of brass in atmospheric environment (Ref 3–6). The phenomenon of dezincification, known as the dealloying process, is a major limiting factor for the use of brass in many service environments. Numerous theories have been proposed concerning the dezincification of brass, which can be divided into two types: selective dissolution mechanism and dissolution–redeposition mechanism. The former describes the preferred dissolution process of Zn, leaving a more stable and porous copper layer on the surface of brass (Ref 7–9). The latter (Ref 10–13), however, depicts a simultaneous dissolution of Xiao Lu and Yuwei Liu, School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China; and Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China; and Hongtao Zhao and Zhenyao Wang, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China. Contact e-mail: zhywang@imr
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