Ion beam sputter coating with the substrate at ambient temperature or water-cooled is a well-known process for coating temperature-sensitive substrates with films of high quality, despite the low process temperature. However, ion beam based methods suffer from an intrinsic drawback, the so-called line-of-sight restriction. Since a directed beam of the material to be deposited is used, only that part of a sample that is "seen" by the particle source is properly treated. This renders coating of 3-dimensional objects with ion beam methods difficult Particularly challenging is to completely coat such objects from all sides. A typical example are rings. When they are to be treated with ion beam techniques, sophisticated manipulation of substrate or ion beam or even both is required. Despite these problems, under certain circumstances it is nevertheless possible to apply ion beam techniques for treating/coating 3-D objects. When ion beam sputter coating is used, the sputter target, i.e. the source of the material to be deposited, is usually flat With such a sputter target, a ring can hardly be coated uniformly. However, when the sputter target is formed according to the substrate shape, here as a concave/convex double cone, a very effective coating can be achieved. This is demonstrated by coating rings for corrosion protection. (C) 2016 Elsevier B.V. All rights reserved.