An improved laboratory reattachment method for the rapid assessment of adult barnacle adhesion strength to fouling-release marine coatings

Abstract

Modifications have been made to the previously described adult barnacle laboratory reattachment method to enhance and improve the overall utility of this technique for rapidly assessing the efficacy of novel fouling-release marine coating technologies. These modifications include the use of an immobilization template to secure barnacles onto the coating surfaces during the underwater reattachment process, the development of a semi-automated push-off device to enable consistent and reproducible force gauge measurements and the implementation of a software tool to measure the diameter of barnacle base plates for adhesion strength calculations. A series of experimental siloxane–polyurethane and control coatings were evaluated with both the original and improved laboratory reattachment methodologies. Significantly higher adhesion strengths were obtained on these coatings using the improved reattachment method. Furthermore, only the improved reattachment method was able to discern significant differences in the performance of the siloxane–polyurethane coatings based on differences in compositional components. In this regard, the siloxane–polyurethane coatings containing the poly-caprolactone end groups attached to the poly(dimethylsiloxane) (PDMS) backbone exhibited significantly higher reattached barnacle adhesion strengths than the aminopropyl-terminated PDMS containing coatings. It was also shown that the utilization of barnacles with 5–6 mm base plate diameters, rather than 7–8 mm diameters, significantly enhanced the strength or tenacity of adhesion to the surface of the control coatings. The results of the improved laboratory reattachment evaluation of experimental siloxane–polyurethane and control coatings were in good agreement with barnacle adhesion measurements obtained for the same coatings with static ocean immersion testing in the field.