Carbon-containing-titania coated stainless steel prepared by high voltage powder spray coating and its adhesion phenomena

Abstract

Nowadays, many studies involve coating materials on stainless steel prepared by various methods, and many approaches have been taken to improve the abrasion resistance of the coatings. Here, the attachment of carbon/titania (C/TiO2) on stainless steel and the evaluation of its coating adhesion is reported. The commercially available epoxy resin was used as the source of carbon, and the transformation from epoxy resin to pyrolytic carbon was performed. It is proposed that the incorporation of an inorganic particle will improve the adhesion properties through the reduction of the carbon shrinkage. C/TiO2 was prepared from the mixture of commercialized epoxy resin (Oxyplast PR12®) and anatase TiO2 powder, followed by spraying the mixture onto stainless steel (AISI 304) surface using high voltage powder spray coating (HVPSC). The sprayed powders on stainless steel underwent pyrolysis at several temperatures from 300 to 700 °C for an hour to determine the optimum temperature for excellent adhesion. The physical properties of C/TiO2 coated samples were characterized by Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), surface profiler meter and X-ray photoelectron (XPS) spectroscopy. The FTIR analysis of C/TiO2 coating identified the appearance of peaks C[sbnd]H sp3, C[dbnd]O, C[sbnd]O, and Ti[sbnd]O. It was noticed that the absorption band of C[sbnd]H sp3, C[dbnd]O, and C[sbnd]O slowly disappeared as the pyrolysis temperature increased, indicating that the structure changed from epoxide to pyrolytic carbon. FESEM images showed that the TiO2 particles were fully covered with the carbon layer, and the thickness was determined to be in the range of 4.8–15.5 μm. The abrasive and peel adhesion test was performed, showing no detachment of coated material of C/TiO2 pyrolyzed at 300 °C, suggesting that this temperature produces the best coating adhesion. The carbon-based coating adhesion phenomena were elucidated by XPS analysis of Fe2p, C1s, and Ti2p element peaks. It was demonstrated that the presence of an oxide layer on stainless steel, availability of functional groups, and structure shrinkage were the factors that affect the adhesion of the carbonaceous coating. The structure shrinkage was reduced due to the presence of TiO2, which is associated with strong coating adhesion. This demonstrated that the carbonaceous coating produced by HVPSC formed an excellent adhesion in the presence of TiO2.