Bacterial adhesion on the surfaces of medical devices, food processing equipment, heat exchangers and ship hulls has been recognized as a widespread problem. Bacterial adhesion on a surface is influenced by surface physical and chemical properties of the surface. In this paper, polyethyleneimine (PEI) grafted graphene oxide (GO) nanosheets were incorporated into Ni–P coatings by an electroless plating technique to modify the surface energy, and therefore to influence the interactions between the prepared surfaces and the tested bacteria. Ni–P–GO coatings were investigated by SEM, AFM, Raman spectrum and XPS. Contact angles of Ni–P–GO coatings with different GO loadings were tested and the surface free energies and their dispersive and polar components were calculated using the van Oss acid–base approach. The results showed that the surface free energies of the coatings had a significant influence on S. aureus adhesion. The Ni–P–GO coatings showed excellent antibacterial adhesion activity. Extended DLVO theory is used to explain the antibacterial adhesion behavior. The novel coatings reported here can be used in controlling bacterial adhesion and biofilm formation for various applications.
Yuxin Wang,Linlin Guan,Zhen He,Shengping Zhang,Harshpreet Singh,Muhammad Dilawer Hayat,Caizhen Yao
Aluminum often requires protective coatings to prevent corrosion. The aluminum alloy substrate usually needs pretreatment to minimize, stabilize or convert the surface oxide in order to achieve adequate coating adhesion. The electrodeposited Ni-P coating is a promising candidate as a protective coating due to its easy fabrication and excellent performance. This study comprehensively investigates the pretreatment of zincating and anodizing on 6061 aluminum alloy, and systematically discusses their influence on the electrodeposited Ni-P coatings. The crystal structure and elemental composition were investigated for interlayers and Ni-P coatings subsequently, while morphologies of the coating surface and cross-section were also determined. The results revealed similar phase composition for differently pretreated Ni-P coatings, while distinct nodule featured morphology was observed for anodized Ni-P coating. It was found that anodized Ni-P coatings had the best performance due to its superior coating adhesion, wear-resistance, and corrosion resistance. In contrast, severe wear damage was occurred to zincated Ni-P coatings due to its inferior microstructure and weak zinc interlayer. Lastly, the influence of anodizing pretreatment on the coating microstructure is discussed, and a model is proposed for Ni-P electrodeposition employing anodizing pretreatment.
Chun Ouyan,Xinlong Zhang,Mingfang Wu,Damao Xun,Pingping Gao
Ni-P coatings including TiN nanoparticles are prepared by electroless plating on Ti plate, which is used as bipolar plates of proton exchange membrane fuel cells (PEMFCs). Scanning electronic microscope (SEM) and X-ray diffraction (XRD) are used to characterize the surface morphology and phases of the coatings, respectively. Corrosion resistance of Ni-P and Ni-P/TiN coatings are measured in the simulated solution of PEMFCs. The interfacial contact resistances (ICR) between carbon paper and bipolar plates are conducted by applied different forces. Potentiostatic polarization tests are prepared at different voltage by bubbling air and H2 at 70 °C, respectively. It is indicated that TiN particles as a core enclosed by Ni-P are entrapped into the coating by SEM images. Comparing to Ni-P coatings, the Ni-P/TiN coating shows better behaviors of corrosion resistance and low ICR. The good corrosion resistance is attributed to the formation of coating and the compact surface morphology. Hence, Ti metal with electroless plating Ni-P/TiN coating is a potential candidate for applying in the bipolar plates of PEMFCs
The corrosion behavior of Ni-P coating deposited on 3003 aluminum alloy in flue gas condensate was investigated by electrochemical approaches. The results indicated that nitrite acted as a corrosion inhibitor. The inhibiting effect of nitrite was reduced in solutions containing sulfate or nitrate. Chloride and sulfate accelerated the corrosion of Ni-P coatings greatly. This can provide important information for the researchers to develop special Ni-P coatings with high corrosion resistance in the flue gas condensate.Keywords:electroless Ni-P coating;anion;3003 aluminum alloy;flue gas condensate;pitting corrosion
The Ni-P/TiN coating was used as bipolar plate by electroless plating on Ti. Surface morphology and phase structure of the coatings were characterized by SEM and XRD, respectively. Corrosion resistance of Ni-P and Ni-P/TiN coating was measured in the simulated solution of Proton exchange membrane fuel cells (PEMFCs). The interfacial contact resistance (ICR) was conducted by applied different forces. SEM images indicated that the particles of core–shell structure were formed on the surface of coating on Ti substrate. The core–shell structure was composed of TiN core and Ni-P electroless plating shell. Compared with Ni-P coatings, the Ni-P/TiN coating showed better corrosion resistance behaviors and low ICR (below 10 m Ω cm − 2 under pressure of 200 N/cm 2 ) . TiN particles and distribution of core–shell were in favor of the formation of coating and compact surface morphology. The good conductivity was attributed to the compact surface morphology of coating. The Ni-P/TiN coating showed excellent interfacial conductivity and good corrosion resistance at applied high potential in simulated solution of PEMFCs.
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