Apple Inc.
Colored multilayer oxide coatings

Abstract:

Colored oxide coatings having multiple oxide layers are described. Processes for forming the multilayer oxide coating can include converting a portion of a metal substrate to a primary oxide layer, coloring the primary oxide layer, and depositing a secondary oxide layer on the primary oxide layer. The primary oxide layer and the secondary oxide layer can be at least partially transparent such that a texture of an underlying metal substrate surface is visible through the multilayer oxide coating. A top surface of the secondary oxide layer can be polished to a high gloss to give the multilayer oxide coating an appearance of depth.