Authors
Abstract
In this study an attempt has been made to formulate materials for glass ceramic enamel coating that can be applied directly onto cast iron substrate for corrosion control. Different 'proportions(4.95) %wt. to form four batches. The batches were mixed with water to form slips which were used to coat already prepared cast iron surfaces and were allowed to dry in the oven. The coated cast iron plates were fired at temperatures of 850˚C to mature and factually heat treated at 680˚C.
The coatings were observed and also chemical tests were conducted to determine the corrosion properties of the resultant coatings. The chemical tests were evaluated using a suitable standard methods and special attention was paid to the type of aggressive solution, and temperature.
The results show that the coatings matured and adhered very well to the sub strateand showed good corrosion resistance in H2SO4,HCl,C6H8O7, H3PO4, and NaOH solutions. The results indicated that the corrosion rate in both acid and alkali media was increased strongly with the increasing temperature.The coatings prepared with the zircon showed better results in terms of acidcorrosion resistance than those prepared with the other crystalline agents. However, the corrosion rate of the zircon containing coating in sulfuric acid was higher than that in hydrochloric acid. Also, it is found that there is absolutely no weight loss for any of the four types of the coating in neither citric nor phosphoric acids. At the same time, the results for alkali corrosion resistance indicate that the act of the four series is very similar to each other, for the four coatings there is no high corrosion rate until the temperature exceed 100˚C after that the rate increases in a very quick manner. From the results it is found that the enamel with lithium oxide was not affected by the alkali solution at all, this behavior is associated with the presence of crystalline β-Spodumene, and β-Eucryptite, which have an extremely high corrosion resistance especially for alkali medium. Mathematical modeling is implemented and regression equations are obtained by using (SPSS) software to predict the experimental data for acid and alkali corrosion rate. Comparing the predicted and measured values gives high prediction accuracy.
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