Citation: Hsiao, V.K.S.; Lin, Y.-C.; Wu, H.-C.; Wu, T.-I. Surface Morphology and Human MG-63 Osteoblasic Cell Line Response of 316L Stainless Steel after Various Surface Treatments. Metals 2023, 13, 1739. https:// doi.org/10.3390/met13101739 Academic Editor: Amir Mostafaei Received: 24 September 2023 Revised: 10 October 2023 Accepted: 12 October 2023 Published: 13 October 2023 Copyright: © 2023 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/). metals Article Surface Morphology and Human MG-63 Osteoblasic Cell Line Response of 316L Stainless Steel after Various Surface Treatments Vincent K. S. Hsiao 1 , Yan-Cheng Lin 2 , Hsi-Chin Wu 2, * and Tair-I Wu 2, * 1 Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou 54561, Taiwan; kshsiao@ncnu.edu.tw 2 Department of Mechanical and Materials Engineering, Tatung University, Taipei 10451, Taiwan; g11001021@o365.ttu.edu.tw * Correspondence: hcwu@gm.ttu.edu.tw (H.-C.W.); tiwu@gm.ttu.edu.tw(T.-I.W.) Abstract: In this study, the effects of three distinct surface treatment techniques on 316L stainless steel were investigated: low-temperature immersion corrosion, shot peening followed by immersion corrosion, and electrochemical corrosion. These techniques were selected with a focus on their potential implications for biomedical implant applications, as research gaps persist in understanding the influence of these treatments. A comprehensive examination of surface alterations was conducted using scanning electron microscopy, Raman spectroscopy, and α-step thin-film thickness profiling. Furthermore, human MG-63 osteoblastic cell line adhesion was evaluated using Liu’s stain and metallographic optical microscopy. Notable differences in cell-adhesion behavior based on the chosen surface treatment methods were observed. Specifically, weak cell adhesion was observed after low-temperature immersion and shot peening followed by immersion corrosion. In contrast, electrochemical corrosion, especially when conducted with a high current density and low corrosive- solution concentration, resulted in a uniformly corroded surface, which, in turn, promoted dense cell adhesion. Porous oxide layers were generated using all three techniques, but the efficacy of shot peening (applied at 1 kg/cm 2 for 20 s) and electrochemical corrosion (using 0.5 M HCl) as promising processes were highlighted by our experimental results. Uniformly dense corrosion pits were produced through electrochemical corrosion, while semicircular grooves with small corrosion pits were the result of shot peening, both of which were found to be favorable for cell adhesion. The superior cell adhesion observed with electrochemical corrosion further emphasizes its suitability for biomedical applications. Keywords: 316L stainless steel; immersion corrosion; shot peening; electrochemical corrosion; cell adhesion 1. Introduction Artificial biomaterials play a critical role in modern health care by serving as substi- tutes for damaged organs or tissues, thus enabling the restoration of physiological function and extending lifespans [1,2]. Therefore, these materials are held to high standards of qual- ity. Biomaterials in a variety of medical devices, surgical instruments, and artificial organs come into contact with body fluids, either intermittently or continuously [3]. Over the past few decades, remarkable advancements have been achieved in the development and implementation of prosthetic devices for human body implantation [4]. Among the various options currently available for orthopedic joint replacement, hip prosthesis implantation has substantially increased in popularity [5,6]. Although the failure rate of hip prostheses remains low, a small percentage of failures may result in a considerable number of cases of implant loosening, which often necessitates revision surgery. In replacement procedures for load-bearing joints, such as the hip or knee, metallic materials are favored because of their mechanical stability [7–10]. Among the most commonly used metallic materials are stainless steel [11,12], titanium alloys [13,14], and cobalt–chrome alloys [15,16]. Because of Metals 2023, 13, 1739. https://doi.org/10.3390/met13101739 https://www.mdpi.com/journal/metals