Corrosion Failure Analysis of Hot-Dip Galvanized Steel in a Room Environment
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TECHNICAL ARTICLE—PEER-REVIEWED
Corrosion Failure Analysis of Hot-Dip Galvanized Steel in a Room Environment Guobin Zhang . Yusen Wang . Shinian Zhang . Chunhe Liu
Submitted: 7 July 2015 / in revised form: 19 August 2015 / Published online: 27 October 2015 Ó ASM International 2015
Abstract A hot-dip galvanized steel fastener on an electromagnetic product was found to be seriously corroded after 16 years of storage in a room environment. Its surface had become rough and lost its metallic luster, and large amounts of corrosion products had accumulated on the surface, with color ranging from light yellow to red brown. To determine the corrosion mechanism, the manufacturing process and storage information of the fastener were first investigated. Pieces of the corroded fastener were sampled; at the same time, the same kind of steel before and after galvanization was prepared as two control samples. The micromorphology and composition of the surface and corrosion were analyzed by scanning electron microscopy, X-ray energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. Based on these analyses, as well as the manufacturing process and storage information, the corrosion mechanism was identified to be that zinc plating first reacted with oxygen, water vapor, and carbon dioxide in the atmosphere to form Zn(OH)2, ZnCO3, and Zn5(CO3)2(OH)6. Subsequently, the iron under the zinc plating reacted with oxygen and water vapor to form Fe(OH)2, Fe(OH)3 or Fe2O3. Keywords Hot-dip galvanized steel Long-term storage Corrosion mechanism
Introduction Owing to its excellent anticorrosive performance and economic advantages, hot-dip galvanized steel is universally used in military equipment, industry, agriculture, building industry, etc. Usually, the corrosion rate of zinc plating is very low in common atmospheric environments. However, a hot-dip galvanized steel fastener on an electromagnetic product was found to be seriously corroded after 16 years of storage in a room environment, as shown in Fig. 1b. It can be seen from Fig. 1 that the fastener’s surface was a relatively flat plane with metallic luster after galvanization, but after corrosion during 16 years of storage, the surface became rough and lost its metallic luster, and large amounts of corrosion products accumulated on the surface, with color ranging from light yellow to red brown. To determine the corrosion mechanism, a survey of the manufacturing process and storage information as well as micromorphology and composition experiments were conducted on the corroded and control samples. The corrosion mechanism was deduced by integrative analyses, based on the experimental results.
Experimental Sampling
G. Zhang Y. Wang S. Zhang C. Liu Institute of Reliability Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China G. Zhang (&) QingHe Building Number Zi 8, Beijing 100085, China e-mail: [email protected]
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Pieces of the corroded fastener with corrosion of lightyellow and r
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