This part of ISO 15181 is one of a series of standards dealing with the sampling and testing of paints, varnishes and related products. This part of ISO 15181 specifies the apparatus and analysis technique for determining copper (based) biocides in artificial seawater which have been extracted from antifouling paints in accordance with ISO 15181-1. It determines the copper-ion concentration and gives the final calculation for the release rate of copper. It has been proven that small changes in certain parameters of the test method can greatly affect the leaching rate of certain biocides, therefore, the release rates are compared against a well-documented reference standard as a means of establishing that test conditions are within normal operating parameters.