In the continuous casting process, the anti-oxidation coating technology for graphite electrodes effectively extends their service life primarily through the dual mechanisms of “physical isolation” and “chemical transformation” to delay the oxidative loss of the electrodes. Graphite electrodes are highly prone to reacting with oxygen at high temperatures, and oxidation consumption on the side surfaces can even account for 50% to 70% of the total consumption. The core of coating technology lies in constructing a barrier on the electrode surface to isolate the carbon substrate from oxygen.
Physical Barrier and Pore Sealing
The most direct function of the coating is to serve as a dense physical film covering the surface of the graphite electrode. Since graphite materials themselves contain many pores and structural defects, these locations are preferential sites for oxidation reactions and also channels for molten metal erosion. Anti-oxidation coatings, through impregnation or coating application, can penetrate into and fill the pores on the electrode surface, forming a continuous covering layer. For example, coatings prepared by sol-gel methods or slurry coating can form a glass phase or ceramic phase after high-temperature sintering, effectively blocking the channels for oxygen diffusion into the interior of the electrode. For graphite nozzles or electrodes used in continuous casting processes, the application of pyrolytic carbon coatings has shown that their nearly pore-free dense structure can significantly inhibit oxidation reactions from beginning to spread from structural defects.
Chemical Transformation and Self-Healing
In addition to physical isolation, many coating systems also utilize chemical transformation mechanisms to achieve more active protection. Specific components in the coating (such as boric acid, borax, silicon carbide, silicon dioxide, etc.) will preferentially react with oxygen that diffuses in at high temperatures. This reaction consumes oxygen, preventing it from contacting the internal carbon. More critically, certain reaction products (such as the glass phase formed by boron oxide) have fluidity and can flow to fill gaps when microcracks appear in the coating, achieving a certain degree of “self-healing” effect, thereby maintaining the integrity of protection in the continuous casting environment with temperature fluctuations. For example, aluminum phosphate coatings with boric acid or borax as additives have been proven to significantly reduce electrode consumption through this mechanism.
Thermal Stress Relief and Bonding Strengthening
In the continuous casting process, graphite electrodes often experience severe temperature changes, so the matching of thermal expansion coefficients between the coating and the graphite substrate is crucial. If the match is improper, the coating is prone to cracking and peeling under thermal shock, instead losing its protective effect. Advanced coating technologies typically employ composite or gradient structure designs. For example, in silicon carbide-alumina-zirconia composite coatings, silicon carbide is often used as a transition layer, whose role is to alleviate the thermal expansion coefficient mismatch between the graphite substrate and the external ceramic coating, enhance bonding strength, and prevent premature failure of the coating during thermal cycling. Similarly, some coating formulations introduce borides as a bottom layer, utilizing their good wettability to graphite at high temperatures to firmly adhere the anti-oxidation surface layer to the electrode.
In summary, in industrial applications related to continuous casting, anti-oxidation coating technology does not rely solely on any single mechanism, but rather through the synergistic effects of densification and pore sealing, high-temperature chemical oxygen consumption, self-healing repair, and stress buffering, jointly slowing down the oxidation rate of graphite electrodes, ultimately achieving the purpose of extending their service life and reducing consumption per ton of steel.
Post time: Sep-17-2026