Enhancement of Corrosion Resistance AISI 304 Steel by Plasma Polymerized Thin Films
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Enhancement of Corrosion Resistance AISI 304 Steel by Plasma Polymerized Thin Films Nazir M. Santos1, Jayr Amorim2, Pedro A.P. Nascente3, Célia M.A. Freire4, Nilson C. Cruz1 and Elidiane C. Rangel1 1
State University of Sao Paulo, Laboratory of Technological Plasmas, UNESP, Sorocaba, SP, Brazil 2 Brazilian Center of Research in Energy and Materials, Brazilian Bioethanol Science and Technology Laboratory, CTBE, Campinas, SP, Brazil 3 Federal University of Sao Carlos, UFSCar, Department of Materials Engineering, São Carlos, SP, Brazil 4 State University of Campinas, UNICAMP, Department of Materials Engineering, Campinas, SP, Brazil ABSTRACT The purpose of this work is the deposition of films in order to increase the corrosion resistance of AISI 304 steel, which is a material used to construct the reactors for bioethanol production. This deposition inhibits the permeation of corrosive species to the film-metal interface. Thin films were prepared by radio-frequency plasma enhanced chemical vapor deposition (RF-PECVD) method using plasmas of hexamethyldisiloxane/argon/oxygen mixtures excited by signals of different powers. The plasma was generated by the application of RF power of 13.56 MHz to the sample holder while keeping grounded the topmost electrode and the chamber walls. The effect of the RF power on the properties of the samples was investigated by perfilometry, X-ray photoelectron spectroscopy (XPS), contact angle, and electrochemical impedance spectroscopy (EIS). The results of the corrosion resistance tests of the AISI 304 steel were interpreted in terms of the energy delivered to the growing layer by plasma excitation power.
INTRODUCTION Silicon hydrogenated amorphous carbon (a-C:H:Si) films have attracted great interest due to their promising properties, such as corrosion resistance [1,2], optical transparency [3], and chemical barrier [4]. They are usually applied as protective coating, optical filters, scratch resistance coatings, and humidity and chemical sensors [5]. These films are usually synthesized by glow discharge techniques as Plasma Enhanced Chemical Vapor Deposition (PECVD) and their properties depend on the conditions of the process such as discharge power, excitation frequency, deposition time, monomer type, pressure, and others. The combination of these parameters determines the chemical structure of the films and makes it possible to prepare the films with properties ranging from organic (polymer-like) to the inorganic polymer (SiOx-like) by varying the deposition parameters [6-9]. The fragmentation of the organic molecule by plasma gives rise to radicals containing Si, H, C, and O, which in turn cause the formation of the films having such species on the substrate surface. Depending on the RF power in the plasma it may occur the molecular dissociation of HMDSO in SiO, Si, CH, C, and H, or the chemical reaction of recombination atoms that compose HMDSO among themselves in H2 and C2, or with
atomic oxygen in OH and CO [10, 11]. The main objective of this work is to enhance the corrosion r
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