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Open AccessArticle

Comparative Study of the Corrosion Resistance of Air-Plasma-Sprayed Ca2SiO4 and Al2O3 Coatings in Salt Water

1
The Key Laboratory of Inorganic Coating Materials CAS, Shanghai Institute of Ceramics, Chinese Academy of Science, Shanghai 201899, China
2
University of Chinese Academy of Sciences, Beijing 100039, China
*
Authors to whom correspondence should be addressed.
Coatings 2018, 8(4), 116; https://doi.org/10.3390/coatings8040116
Received: 11 January 2018 / Revised: 15 March 2018 / Accepted: 19 March 2018 / Published: 22 March 2018
(This article belongs to the Special Issue Advanced Coatings for Corrosion Protection in Extreme Environments)
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Abstract

In this study, Ca2SiO4 coating was sprayed on stainless steel substrate and the corrosion resistance of the as-sprayed coating was studied in salt water. At the same time, Al2O3 coatings were produced by air-plasma-sprayed technology as comparison. Immersion test was carried out to evaluate the protection performance of coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) plots were also analyzed. The results indicated that Ca2SiO4 coatings showed a better protection performance than Al2O3 coatings. During the immersion, various calcium carbonate crystals appeared on the surface of Ca2SiO4 coatings. Ca(OH)2 was released from Ca2SiO4 coatings into NaCl aqueous solution, increasing the alkalinity, which is in favor of the formation of passivation film, and thus improves the corrosion resistance. Ca2SiO4 coatings became denser after immersion due to the fact that the pores and micro cracks were filled with hydration products i.e., hydrated calcium silicate (C–S–H) gel. On the contrary, the microstructure of Al2O3 coatings became loose and obvious rusty spots were observed on the surface after the immersion test. View Full-Text
Keywords: dicalcium silicate coating; alumina coating; hydration; passivation film; corrosion resistance dicalcium silicate coating; alumina coating; hydration; passivation film; corrosion resistance
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Xiao, Y.; Shao, F.; Zhuang, Y.; Ni, J.; Zhao, H.; Tao, S. Comparative Study of the Corrosion Resistance of Air-Plasma-Sprayed Ca2SiO4 and Al2O3 Coatings in Salt Water. Coatings 2018, 8, 116.

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