Papers by Keyword: Enamel Coating

Abstract: In this work, a porcelain enamel coating material for high temperature resistant on 1Cr18Ni9Ti stainless steel is designed and processed. The structure and properties of the material are analyzed by SEM, EDAX, XRD and FTIR. The results show that the surface of the enamel glaze and the enamel coating are smooth and bright, there is no obvious crystallization characteristics in porcelain enamel. There is litter oxidation and inter-diffusion in the interface between 1Cr18Ni9Ti stainless steel and porcelain enamel coating material after coating enamel.

Abstract: Reinforcing steel bars coated with pure enamel and fusion-bonded epoxy (FBE) were immersed in 3.5 wt.% NaCl solution for a period of 84 days. Predetermined damage of the coatings was created with a standard impact tester to study the coating resistance to potential damage caused during transportation and construction. Open-circuit potential and electrochemical impedance spectroscopy (EIS) tests were used to investigate deterioration processes of the two coating systems. An equivalent electrical circuit model was established to extract corrosion-indicative dielectric properties of enamel and FBE coatings from the EIS data. The change of coating capacitance over time was represented by a diffusion-controlled process. In comparison with the FBE coating with the same extent of damage, the enamel coating corroded sooner due to its thinner layer and porous microstructure, but deteriorated more slowly due to its robust bond with the steel substrate.

Abstract: The enamel powder was preseted on the Ti alloy by electrophoresis, and the enamel coatings were obtained through sintering. Friction and abrasion performance of the enamel coatings and RE enamel coatings were compared. The results show that the RE element improved the inner organizational structure of the enamel coating, decreased the friction coefficient of the coating and consequently improved the friction-resistant character of the enamel coatings. By adding RE, the viscidity, suspension and fluidity of the enamel coatings are improved, and that the microstructure of the enamel coating are more dense and the horniness grain phase was more small in uniform during sintering.

Abstract: In this study, the corrosion process of enamel-coated deformed rebar completely immersed in 3.5 wt.% NaCl solution was evaluated over a period of 84 days by EIS testing. Three types of enamel coating were investigated: pure enamel, 50/50 enamel coating, and double enamel. Surface condition of the enamel coatings that were intentionally damaged prior to corrosion tests was visually examined at different immersion times. After 84 days of testing, the damaged coating areas were characterized by SEM, and the corrosion products on and adjacent to the damaged areas were collected and analyzed by XRD. Corrosion initiated at the damaged locations with no undercutting of the coating observed. The 50/50 enamel coating had the least corrosion resistance, due to its interconnected pore structure, and prior damage drastically reduced the corrosion resistance of pure and double enamel coated rebar.

Abstract: Because the enamel coatings has excellent ageing resistance and anti-corrosion performance, the service life of pipeline with enamel coatings as protective layer can be increased remarkably comparing with the ones with organic coatings. But when the pipeline is welded, the high temperature of welding arc will do harm to the bonding strength of the enamel coating and the base metal because of the differences of thermo-physical properties between them. In order to study the failure mechanism of enamel coating in the heat affected zone, the stress changing process of enamel/steel was studied through numerical simulation and the interface of enamel/steel was studied by welding thermal simulation technology. The results show that the weakness parts of the welded joints are the imperfect normalized zone and overheated zone. In the imperfect normalized zone, the micro-cracks generate at the interface of enamel/steel because high stress occurred and some coatings fused incompletely because of short staying time at high temperature that induced micro-cracks in the enamel coating under high welding stress, so it was one of the dangerous zones of HAZ. Because high tensile stress formed during cooling that was dangerous to the brittle enamel coating, the bond layer of enamel/steel was damaged by high temperature of welding and the pores generated at the interface of enamel/steel, the coatings of overheated zone could be pulled off from the base metal easily that caused the steel exposed to the corrosion medium directly without the protection of enamel coating, so it was another dangerous zone of HAZ. Keywords: enamel coating; numerical simulation; welding thermal simulation; failure mechanism; HAZ