Corrosion protection of stainless steel by polysiloxane hybrid coatings prepared using the sol–gel process

Abstract

Polysiloxane hybrid films were deposited on 316 L stainless steel substrates by dip-coating in a sol prepared by acid-catalyzed hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyltrimethoxysilane (MPTS), followed by radical polymerization of methacrylic moieties. Structural features of the polysiloxane hybrids were studied using 13 C and 29 Si nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA), as a function of the TEOS/ MPTS ratio, which ranged between 0 and 2. The efficiency of corrosion protection of hybrid-coated stainless steel was investigated by X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) after immersion of the material in acidic and neutral saline aqueous solutions. The NMR and TGA results indicated a high degree of polymerization and polycondensation (85%) for the hybrid film with a TEOS/MPTS ratio of 2, as well as elevated thermal stability of 410°C and excellent adhesion. The XPS analysis confirmed the hybridized structure of the polysiloxane network, and showed that no corrosion-induced changes had occurred on the coated steel surface after 3 weeks of immersion in 3.5% NaCl solution. Potentiodynamic polarization curves showed that the hybrid coating prepared using a TEOS/MPTS ratio of 2 yielded the best anti-corrosion performance. It acts as an efficient physical barrier, increasing the total impedance and reducing the current densities by 2 orders of magnitude, compared to the bare electrode. The impedance results obtained for the two electrolytes were discussed based on the electrical equivalent circuits used to fit the experimental data.

Corrosion Resistant Coatings Based on Organic-Inorganic Hybrids Reinforced by Carbon Nanotubes

“…This allows to design specific characteristics of the material for a wide range of applications. Different forms of organic-inorganic hybrids have been intensively studied due to their interesting mechanical, optical and thermal properties (Zheludkevich et al, 2005), resulting in a number of applications such as drug delivery systems, sensors, electrical and optical devices, catalysts and protective coatings (Landry et al, 1992;Sarmento et al, 2010). Due to their inert and nontoxic nature, hybrid coatings are considered among the existing corrosion inhibitors as the most promising candidates for environmentally compliant surface protection.…”

Development of hybrid coatings for osseointegration improvement of metal dental implants

“…Finally, above 500ºC the slight weight loss registered may be related with the decomposition of the polymeric structure and the dehydration of silanol groups. 21,[23][24][25][26] The results show that the gelatin incorporation does not affect the thermal degradation behavior of the biomaterial. All the same, it is important to refer the slight differences on the derivative chart identified at below 270ºC related with water evaporation and volatiles evaporation.…”

“…The next peak identified at ≈350-600ºC is associated with the volatilization of small molecular oligomers or unreacted precursors. 21,[23][24][25][26] Interestingly, below 270ºC the materials show different character, specifically pure 56M:14G:30T show two peaks at 140ºC and 220ºC related with water evaporation (≈2%) and volatiles evaporation (≈2,5%)…”

“…19 Another source of Si can be its use directly as orthosilicic acid (Si(OH) 4 as silicates are poorly soluble and usually form silicic acid or uncharged molecules in order to dissolve. 20,21,22,23,24,25 The employment of a bio-absorbable osteoconductive coating on different kinds of prosthesis that release silicon during its degradation process represents an extra strategy to provide silicon to the bone damage area stimulating osteoblastic activity.…”

“…19 Otra fuente de Si es su uso directo cómo ácido ortosilícico (Si(OH) 4 , una vez que los silicatos son poco solubles y por lo general forman ácidos silícicos o moléculas eléctricamente neutras para disolución. 20,21,22,23,24,25 El empleo de un revestimiento osteoconductor biológicamente absorbido en diferentes tipos de prótesis capaces de liberar silicio durante el proceso de degradación representa una estrategia adicional para proporcionar silicio a la zona ósea dañada estimulando la actividad osteoblástica.…”