Evaluation of 316L stainless mill additives on microstructure and alkali corrosive behavior of enamel coatings

Abstract

AbstractExcellent chemical stability, good corrosion resistance, and compositional controllability make vitrified enamel promising coating materials. The corrosion resistance of the [–Si–O–]/[–Si–O–Al–]‐based enamel coatings decreases in alkaline environments, whereas can be improved by incorporating metal oxides, such as ZrO2 and SnO2. The introduction of these oxides results in an increase in the sintering temperature and a decrease in the toughness of the coatings. It was observed that the corrosion resistance of the coatings in an alkaline medium could be improved using metal powder‐based additives without increasing the sintering temperature and affecting the mechanical properties of the coatings. We used powdered 316L stainless steel as the mill additive, and the effects of this additive on the structure and alkali corrosion resistance of the vitrified enamel coatings were studied. Results indicate that the addition of an appropriate quantity of the additive (4 wt.%) improves the extent of gas consumption during the enamel sintering, decreases the degree of porosity and the size of the pores. Furthermore, the mechanical properties of the skeleton formed between the pores could be improved, because blocklike corrosion products are not peeled off, which increases the corrosion resistance of the coatings. The corrosion products, such as Ca‐based compounds, block the corrosion holes, resulting in a decrease in the corrosion rate also.