Measuring and modelling the appearance of coated steel surfaces

The appearance of an object is strongly influenced by the reflective properties of its surface. These properties are governed by the optical constants of the material, its roughness and the thickness and optical properties of the coatings. In this paper we study rough steel substrates covered with thermal grown oxide layers. The optical constants, thickness and roughness of the sample were measured and they were used as parameters in a model to simulate the reflection of the samples. These simulated reflections correspond well with experimental scatterometry measurements. Using these data we were able to predict the colour and the gloss of the samples. This opens the possibility to design the colour and the gloss of coated steel according to the wishes of the users.