ISO 9211 (series) describes surface treatments of components and substrates excluding ophthalmic optics (spectacles) by the application of optical coatings and gives a standard form for their specification. It defines the general characteristics and the test and measurement methods whenever necessary, but it is not intended to define the process method.

This document specifies general use and standard categories of use for optical coatings and identifies which environmental tests are necessary to prove that the coatings meet the required specification. The mechanical and chemical properties of coated optical elements, and more generally their environmental durability, can be assessed by a variety of methods. The test methods are generally described in various parts of ISO 9022 and in ISO 9211‑4. These test methods are selected to give meaningful results representative of actual exposure of optical elements in their operating environment, alternatively to the minimum requirements as described in ISO 9211‑5 to ISO 9211‑8, which are coating type related.