Abstract

Polytetrafluoroethylene (PTFE) was coated on 316L stainless steel (SS) substrate through a spin coating technique to enhance its corrosion resistance properties in hydrochloric acid (HCl) and nitric acid (HNO3) medium. Scanning electron microscopy (SEM) revealed the morphology of the coated and uncoated substrates and showed a uniform and crack-free PTFE coating on 316L SS substrate, while a damaged surface with thick corrosive layers was observed after the electrochemical test on the uncoated sample. However, an increased concentration of HCl and HNO3 slightly affected the surface morphology by covering the corrosive pits. An atomic force microscope (AFM) showed that the average surface roughness on 316L SS and PTFE coating was 26.3 nm and 24.1 nm, respectively. Energy dispersive X-ray spectroscopy (EDS) was used for the compositional analysis, which confirmed the presence of PTFE coating. The micro Vickers hardness test was used to estimate the hardness of 316L SS and PTFE-coated substrate, while the scratch test was used to study the adhesion properties of PTFE coating on 316L SS. The anticorrosion measurements of 316L SS and PTFE-coated substrates were made in various HCl and HNO3 solutions by using the electrochemical corrosion test. A comparison of the corrosion performance of PTFE-coated substrate with that of bare 316L SS substrate in HCl medium showed a protection efficiency (PE) of 96.7%, and in the case of HNO3 medium, the PE was 99.02%, by slightly shifting the corrosion potential of the coated sample towards the anodic direction.

Highlights

  • Stainless steels (SS) are the most commonly used materials in different engineering applications, mainly because of their enhanced mechanical and excellent corrosion resistance properties

  • A uniform PTFE coating was successfully deposited on 316L SS substrate by using the spin coating

  • A uniform PTFE coating was successfully deposited on 316L SS substrate by using the spin coating technique

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Summary

Introduction

Stainless steels (SS) are the most commonly used materials in different engineering applications, mainly because of their enhanced mechanical and excellent corrosion resistance properties. These properties extend their use to making different biomaterials for use in the manufacturing of various medical devices [1,2]. The local breakdown in passivity occurs mainly at sites of local heterogeneities, causing pitting corrosion [11,12], and corrosion can occur under high temperatures and high pressure stress [13] For these reasons, stainless steels may need to be improved by corrosion protection. A number of innovative techniques are currently under intensive study to improve the corrosion behavior of stainless steel, such as sol-gel deposition [14,15], chemical vapor deposition [16], plasma-nitriding [17], plasma detonation techniques [18], high-velocity oxy-fuel spray (HVOF) [19]

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