ISO 2177:2002 describes a coulometric method by anodic dissolution for measuring the thickness of metallic coatings. It is only applicable to conductive coatings. Typical combinations of coatings and substrates that can be tested by this method are given. Other combinations may be tested with electrolytes in current use, or new electrolytes may be developed for them but, in both cases, it is necessary to verify the suitability of the complete system. ISO 2177:2002 is also applicable to multi-layer systems, e.g Cu-Ni-Cr. It may be used to measure the thickness of coatings applied by various means, if due account is taken of special features such as the presence of an alloy layer. In some cases, the presence and thickness of diffusion layers can also be measured. It can also be used to measure the thickness of coatings on cylindrical specimens and wires.