Lower Frictional Resistance Characteristics of Foul Release Systems

Abstract

This chapter investigates the roughness and drag characteristics of two antifouling paint systems: a state-of-the-art (tributyl)tin-free self-polishing copolymer (SPC) and a nontoxic foul release system. Towing tank experiments confirmed that the total resistance of a 6.3 meters long plate coated with the foul release coating system was on average 1.4% lower than when it was coated with the tin-free SPC. The roughness characteristics were measured with both a stylus instrument and an optical measurement system. Correlation with the measured drag shows that the roughness of the foul release cannot be characterized solely by a height parameter, such as the parameter Rt50. Surface profilometry of coated sample plates shows that the texture of a foul release surface is significantly different from the texture of a tin-free SPC surface, exhibiting a low-amplitude undulating character. To correlate the roughness functions measured from the drag experiments with the surface characteristics, it is necessary to take a measure for the texture into account, in addition to a measure for the height of the profile.