Dmitry Leonidovich Kovalenko, Vy Uong Van, Van Phuc Mac, Thien Vuong Nguyen, Lan Pham Thi, Tuan Anh Nguyen, Vladimir Evgenevich Gaishun, Vasili Vasilievich Vaskevich and Dai Lam Tran
This paper aims to explore how graphene can improve the mechanical and anti-corrosion properties of TiO2-SiO2 sol-gel coating. This sol-gel coating has been prepared on aluminum…
Abstract
Purpose
This paper aims to explore how graphene can improve the mechanical and anti-corrosion properties of TiO2-SiO2 sol-gel coating. This sol-gel coating has been prepared on aluminum alloy substrate using graphene as both nano-filler and corrosion inhibitor.
Design/methodology/approach
To examine the effect of graphene on mechanical properties of sol-gel coating, the abrasion resistance, adhesion strength and scratch resistance of coating have been evaluated. To reveal the effect of graphene on the anti-corrosion property of coating for aluminum alloy, the electrochemical impedance spectroscopy (EIS) has been conducted in 3.5 Wt.% NaCl medium.
Findings
Scanning electron microscopy images indicate that graphene nanoplatelets (GNPs) have been homogeneously dispersed into the sol-gel coating matrices (at the contents from 0.1 to 0.5 Wt.%). Mechanical tests of coatings indicate that the graphene content of 0.5 Wt.% provides highest values of adhesion strength (1.48 MPa), scratch resistance (850 N) and abrasion strength (812 L./mil.) for the sol-gel coating. The EIS data show that the higher content of GNPs improve both R1 (coating) and R2 (coating/Al interface) resistances. In addition to enhancing the coating barrier performance (graphene acts as nanofiller/nano-reinforcer for coating matrix), other mechanism can be at work to account for the role of the graphene inhibitor in improving the anticorrosive performance at the coating/Al interface.
Originality/value
Application of graphene-based sol-gel coating for protection of aluminum and its alloy is very promising.
Thi Thanh Huong Nguyen, Nam Pham Thi, Thang Le Ba, Vy Uong Van, Bao Le Duc and Tuan Anh Nguyen
This study aims to enhance to corrosion protection of NiZn-plated steel by electroplating multilayer coating.
Abstract
Purpose
This study aims to enhance to corrosion protection of NiZn-plated steel by electroplating multilayer coating.
Design/methodology/approach
The multilayer coating consists of three layers on mild steel substrate, such as Cr3+ chromate conversion layer (CCC), electrodeposited nanosilica zinc-nickel composite layer (ZnNiSi) and electrodeposited zinc-nickel alloy layer (ZnNi). Its morphology, composition and corrosion behaviour were investigated by various methods.
Findings
Polarization curves indicated that polarization resistance and corrosion current density of CCC/ZnNiSi/ZnNi/Fe (6.956 kO.cm2; 2.56 µA.cm−2) were two times higher and five times lower than that of ZnNiSi/ZnNi/Fe (3.42 kO.cm2; 12.52 µA.cm−2), respectively. From electrochemical impedance spectroscopy data, charge transfer resistances were 1.344, 2.550 and 2.312 kO.cm2 for ZnNi, ZnNiSi/ZnNi and CCC/ZnNiSi/ZnNi, respectively. Salt spray test indicated that after 48 h, surface of ZnNi and ZnNiSi was covered by white rust, whereas no white rust was observed on surface of CCC/ZnNiSi/ZnNi. After 600 h, there were red rust spots (1% surface coverage) on surface of Zn-Ni, whereas only white rust was observed on both ZnNiSi/ZnNi (100% surface coverage) and CCC/ZnNiSi/ZnNi (10% surface coverage).
Originality/value
Multilayer coating enhanced significantly the corrosion protection for steel, as compared to the single-layer coating.