Novel Hydrophobic Nanostructured Antibacterial Coatings for Metallic Surface Protection

Mariana-Gratiela Vladu,Adi Ghebaur,Claudia Mihaela Ninciuleanu,Ioana Catalina Gifu,Ludmila Otilia Cinteza,Cristian Petcu,Sabina Georgiana Burlacu,Lenuta Stroea,Cristina Lavinia Nistor,Daniela Bala,Catalin Ionut Mihaescu

doi:10.3390/coatings12020253

Abstract

A simple and cost-efficient method to modify different surfaces in order to improve their bioactivity, corrosion and wear resistance proved to be sol-gel coatings. The silane layers have been shown to be effective in the protection of steel, aluminum or magnesium alloys and copper and copper alloys. Moreover, it has been found that the adding of different inorganic nanoparticles into silica films leads to increasing their performance regarding corrosion protection. In this study, we fabricated, a simple sol-gel method, transparent mono- and bi-layered hydrophobic coatings with simultaneous antibacterial, hydrophobic and anti-corrosive properties for the protection of metallic surfaces against the action of air pollutants or from biological attacks of pathogens. The first layer (the base) of the coating contains silver (Ag) or zinc oxide (ZnO) nanoparticles with an antibacterial effect. The second layer includes zinc oxide nanoparticles with flower-like morphology to increase the hydrophobicity of the coating and to improve corrosion-resistant properties. The second layer of the coating contains a fluorinated silica derivative, 1H,1H,2H,2H-perfluorooctyl triethoxysilane (PFOTES), which contributes to the hydrophobic properties of the final coating by means of its hydrophobic groups. The mono- and bi-layered coatings with micro/nano rough structures have been applied by brushing on various substrates, including metallic surfaces (copper, brass and mild steel) and glass (microscope slides). The as-prepared coatings showed improved hydrophobic properties (water CA > 90°) when compared with the untreated substrates while maintaining the transparent aspect. The corrosion resistance tests revealed significantly lower values of the corrosion rates recorded for all the protected metallic surfaces, with the lowest values being measured for the bi-layered coatings containing ZnO particles, both in the first and in the second layers of the coating. Considering the antibacterial activity, the most effective were the AOAg-II and AOZnO-II coatings, which exhibited the highest reduction of microbial growth.

Highlights

Due to their special importance in the field of engineering, a variety of protective coatings for metal surfaces have been developed in order to preserve or delay the degradation processes
For the morphological characterization (AFM and scanning electron microscopy (SEM) images), the mono- and bilayer coatings prepared in this study were deposited by brushing on microscope glass slides, in the form of thin films
The results obtained by the SEM images revealed that the flower-like Zinc oxide (ZnO) particles from the second layer of the coatings do not uniformly cover the first layer, but present discontinuities

Summary

Introduction

Due to their special importance in the field of engineering, a variety of protective coatings for metal surfaces have been developed in order to preserve or delay the degradation processes. It was observed that chemical attack is often accompanied by erosion and wear of the metal surface, which causes the physical degradation of the object [1]. Choosing the most effective method of protection is often complicated and depends mainly on environmental conditions, coverage performance and financial cost. The latter includes the initial cost of application and the replacement of corroded parts and, in some cases, the complete renewal of the protecting coat [2]

Methods

Results

Discussion

Conclusion