Preparation of sol-gel SiO2 coatings on steel and their corrosion resistance

Irina Stambolova,Lyuben Lakov,Vladimir Blaskov,Bojidar Jivov,Stancho Yordanov,Sasho Vassilev,V.M Vassilev,Y.P Ivanova,S.G Nikolov,M.D Datcheva

doi:10.1051/matecconf/201814505011

Abstract

A protective SiO2 coating was prepared by sol-gel method on stainless steel plates, using precursor solutions having 2 different concentrations: low (0.5M) and high (2M) concentration. The dip coating-drying cycles have been repeated three times, after that the coatings were thermally treated at 300°C or 500°C in air. Scanning electron microscopy (SEM), AFM and X-ray diffraction analyses have been applied. The corrosion resistances of SiO2 coated steels were examined in NaCl medium for 346 hours. Many microcracks and craters in the samples, prepared from solution of high concentration appear after corrosion attack. The coatings obtained from solution of low concentrations reveals almost unchanged surface structure without visible cracks and pits. The evaluated corrosion rate of this coating is lower than those of uncoated steel.

Highlights

The addition of catalysts increases the hydrolysis rate
X-ray diffraction (XRD) analyses revealed that all samples are amorphous,since no sygnals of crystallized SiO2 were observed
The silica films surface, prepared from 0.5 M TEOS solution is relatively dense with some crystal imperfections (Fig 2-a)

Summary

Introduction

The addition of catalysts increases the hydrolysis rate. The type of catalyst determines the pH of sols and affects the form of sol-gel materials, obtaining the films, powders or monoliths. The proper selection of synthesis parameters and the way of preparing materials is significant in successful sol–gel synthesis. These advantages make the sol–gel process one of the most appropriate technologies for preparation of thin, nanostructured films. Different sol-gel coatings have been developed to increase the corrosion resistance of metals, the pure inorganic films have limitations such as micro cracks, residual porosity and thickness limitations [26, 27]. The aim of this work is the obtaining of protective SiO2 layers by sol-gel method (dip coating technique) on stainless steel plates and investigation their surface morphology, phase composition and chemical stability in salty solution of NaCl

Objectives

Results

Conclusion