In addition to these natural appearance patina surfaces, there are a number of induced finishes which can be created on steels. Many people want to reproduce the look of mill-finish steel. This is possible, but will require maintenance in exterior environments.
Blackened steel is an artistic surface with a historic appearance. It can be made in a number of ways. One such method uses blackening or bluing chemical agents. These can be applied in a controlled environment to bring the steel to an artistic and blackened state. There are a number of patina solutions which can darken the steel for artistic effect. A blackened surface can be also created on galvanized steel sheet, which is essentially a steel with a zinc surface. This black patina is created by chemically patinating the zinc surface to a blackened state.
Heating the steel surface in the presence of steam creates a blue tone. This process, known as bluing, will create a more corrosion-resistant surface, at least for interior exposures. Other bluing processes using proprietary chemistries are available. It is possible to seal the surface with clear coatings or wax to maintain the color and resist further oxidation.