ISO 4628-3:2016 specifies a method for assessing the degree of rusting of coatings by comparison with pictorial standards.

The pictorial standards provided in this part of ISO 4628 show coated steel surfaces which have deteriorated to different degrees by a combination of rust broken through the coating and visible underrust.

NOTE 1 The pictorial standards have been selected from the "European rust scale" published by the European Confederation of Paint, Printing Ink and Artists' Colours Manufacturers' Associations (CEPE), Brussels. The correlation between the ISO scale and the "European rust scale" is given in Annex B, Table B.1.

NOTE 2 The correlation between the ISO scale and the rating system of ASTM D 610 is given in Annex B, Table B.2.

NOTE 3 The rust formation on uncoated steel surfaces is designated in accordance with ISO 8501-1 (rust grades A, B, C, and D).

ISO 4628-1 defines the system used for designating the quantity and size of defects and the intensity of changes in appearance of coatings and outlines the general principles of the system. This system is intended to be used, in particular, for defects caused by ageing and weathering, and for uniform changes such as colour changes, for example yellowing.