coatings Article Effects of Surface Pretreatment of Titanium Substrates on Properties of Electrophoretically Deposited Biopolymer Chitosan/Eudragit E 100 Coatings Lukasz Pawlowski 1, * , Michal Bartma ´ nski 1 , Aleksandra Mielewczyk-Gry ´ n 2,3 and Andrzej Zieli ´ nski 1   Citation: Pawlowski, L.; Bartma ´ nski, M.; Mielewczyk-Gry ´ n, A.; Zieli ´ nski, A. Effects of Surface Pretreatment of Titanium Substrates on Properties of Electrophoretically Deposited Biopolymer Chitosan/Eudragit E 100 Coatings. Coatings 2021, 11, 1120. https://doi.org/10.3390/ coatings11091120 Academic Editor: Maria Vittoria Diamanti Received: 25 August 2021 Accepted: 13 September 2021 Published: 15 September 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Faculty of Mechanical Engineering and Ship Technology, Gda´ nsk University of Technology, 80-233 Gda ´ nsk, Poland; michal.bartmanski@pg.edu.pl (M.B.); andrzej.zielinski@pg.edu.pl (A.Z.) 2 Faculty of Applied Physics and Mathematics, Gda ´ nsk University of Technology, 80-233 Gda´ nsk, Poland; alegryn@pg.edu.pl 3 Advanced Materials Centre, Gda ´ nsk University of Technology, 80-233 Gda´ nsk, Poland * Correspondence: lukasz.pawlowski@pg.edu.pl; Tel.: +48-883-797-081 Abstract: The preparation of the metal surface before coating application is fundamental in deter- mining the properties of the coatings, particularly the roughness, adhesion, and corrosion resistance. In this work, chitosan/Eudragit E 100 (chit/EE100) were fabricated by electrophoretic deposition (EPD) and both their microstructure and properties were investigated. The present research is aimed at characterizing the effects of the surface pretreatment of titanium substrate, applied deposition voltage, and time on physical, mechanical, and electrochemical properties of coatings. The coating’s microstructure, topography, thickness, wettability, adhesion, and corrosion behavior were examined. The applied process parameters influenced the morphology of the coatings, which affected their properties. Coatings with the best properties, i.e., uniformity, proper thickness and roughness, hy- drophilicity, highest adhesion to the substrate, and corrosion resistance, were obtained after deposition of chit/EE100 coating on nanotubular oxide layers produced by previous electrochemical oxidation. Keywords: coatings; titanium; chitosan; eudragit; nanotubular titanium oxide; adhesion; thickness; topography; wettability; corrosion resistance 1. Introduction The surface of titanium biomaterials for bone implants is usually subjected to modifi- cations aimed at improving osteointegration properties, providing resistance to corrosion, or delivering a therapeutic substance to the perivascular tissues. For this purpose, the sur- face layer of the implant is modified or a specific coating is deposited [1–4]. The coatings for implants should be characterized by high adhesion to metallic substrates under shear stresses, suitable roughness, and high resistance to corrosion phenomena [5]. Nevertheless, such structures often exhibit a weak adhesion to the metallic substrate, which is exposed to heavy loads during the implantation procedure [6]. Coating delamination is one of the leading causes of the failure of biomedical implants with surface coatings [7]. The sur- face roughness of such systems is unfavorable for bonding the implant to the tissue or they degrade when exposed to the aggressive environments of the human body [8]. One of the key factors and which is rarely studied concerns the influencing of the properties of the produced layers and coatings as the method of pretreatment of the biomaterial surface before deposition [9,10]. There is a wide range of methods for implant surface preparation that affect its proper- ties including, among others, surface roughness, surface charge, surface energy, and chemi- cal composition. Such factors determine the performance of the deposited coatings [11]. Among the methods of surface preparation, mechanical grinding [12,13], electrochemical polishing [14], etching [15,16], sandblasting [17,18], and chemical passivation [5,19] can be distinguished. Coatings 2021, 11, 1120. https://doi.org/10.3390/coatings11091120 https://www.mdpi.com/journal/coatings