In order to prevent rusting the cast iron cookware body will apply with vegetable oil during transportation, it is normal to be blackening at the beginning and it do not contain harmful substances. And this maintenance applied on cast iron BBQ grid as well.
At the beginning of cooking, be sure to fully heat before putting cooking oil, and then put food after the oil heats up. Avoid cold pot cold oil. Don't make starchy foods at the beginnings can achieve non-stick effect in the later stage.
Cast-iron pans and BBQ grids are made from sand molds, and polished by hand. The body in and out have not been machine polished, so the surface will not as smooth as stainless steel and fine iron kitchen utensils, so the finished products may form unavoidable shallow pits, these are not quality issues.
After use, if there is any water stain on the pot body, please dry it and store it to avoid rusting. The effect of applying vegetable oil on the surface is better. Don't worry if there is a little rust, in case rust please clean the rust stains first and then repeat the first step.