Abstract: A metal article such as a gas turbine component may include a super-diffusion coating with unusually high content of the desired constituent. The coating may be provided by combining two or more diffusion coating processes, each process interdiffusing the desired constituent with the metal article from a different metal source. The metal article can be placed in physical contact with a metal source in powder form as a first source, and the article can also be exposed an additional metal vapor source. Super-chromide coatings can be produced with alpha-chrome content in a manner that also provides the coating with sufficient ductility for long-term durability. For example, a shank portion of a gas turbine blade may be provided with a chromide coating with at least a portion of the coating having from 60-90% chromium content.