The coatings based on carbon nanotubes (CNTs) are increasingly developed for their applications, among others, in medicine, in particular for implants in implantology, cardiology, and neurology. The present review paper aims at a detailed demonstration of different preparation methods for such coatings, their performance, and relationships between deposition parameters and microstructure and material, mechanical, physical, chemical, and biological properties. The thermal and electrostatic spraying, electrophoretic and electrocathodic deposition, and laser methods are presented. Characterization of microstructure of coatings, topography, morphology, adhesion of CNTs to a substrate, mechanical behavior, corrosion resistance, wettability, cytotoxicity, bioactivity, and antibacterial protection are reviewed for different deposition methods and parameters. The state-of-the-art in the field of carbon nanotubes shows a considerable number of research performed on CNTs coatings. The different forms of CNTs, deposition methods, parameters, and substrates were applied as process variables. The microstructures and surface homogeneity, chemical and phase compositions, mechanical properties at the micro- and nanoscale such as coating Young`s modulus and hardness, interface adhesion strength and delaminating force, open corrosion potential and corrosion current density, contact angle in wettability assessment, and bioactivity, cytotoxicity, and antibacterial efficiency among biological properties were determined. The summary of so far achievements, strengths and weaknesses, and important future research necessary for clarification of some weak points, development of non-toxic, mechanically and chemically resistant, bioactive, and antibacterial multicomponent coatings based on functionalized CNTs are proposed.

Preparation and properties of composite coatings, based on carbon nanotubes, for medical applications
    Abstract
    1 Introduction
    2 Forms of carbon nanotubes
    3 CNTs-containing coating types and their deposition methods
        3.1 Thermal spraying
            3.1.1 Plasma spraying
            3.1.2 Cold spraying
            3.1.3 High-velocity oxy-fuel thermal spraying
            3.1.4 Low-velocity oxy-fuel thermal spraying
        3.2 Electrochemical methods
            3.2.1 Electrostatic spraying
            3.2.2 Electrophoretic deposition
            3.2.3 Electrocathodic deposition
        3.3 Laser methods
    4 Properties of composite coatings
        4.1 Topography and morphology
        4.2 Adhesion between CNTs and metallic substrate
            4.2.1 Adhesion mechanisms
            4.2.2 Testing methods and adhesion strength of CNTs
        4.3 Mechanical behavior
        4.4 Corrosion resistance
        4.5 Wettability
        4.6 Bioactivity and cytotoxicity
        4.7 Antibacterial efficiency
        4.8 Perspectives and challanges
    5 Conclusions
    References

• Dorota Rogala‑Wielgus(Division of Biomaterials Technology, Institute of Manufacturing and Materials Technology, Faculty of Mechanical Engineering and Ship Technology, Gdansk University of Technology, 11/12 Narutowicza Str., 80‑233 Gdańsk, Poland) Corresponding author
• Andrzej Zieliński(Division of Biomaterials Technology, Institute of Manufacturing and Materials Technology, Faculty of Mechanical Engineering and Ship Technology, Gdansk University of Technology, 11/12 Narutowicza Str., 80‑233 Gdańsk, Poland) Corresponding author