Biofouling – when Adhesion is a Double-edged Sword
All seafaring vessels are under constant attack by marine organisms which adhere and accumulate on underwater hulls – a process known as biofouling. Adhesion plays a critical role in the biofouling process and also in the antifouling process since proper adherence of antifouling coatings is essential to their long term performance. This application report presents new adhesion and zeta potential characterization methods of marine antifouling coatings by means of instrumented scratch testing and electrokinetic solid surface analysis.
The maritime industry spends billions of dollars a year battling sticky bacteria, algae, and mollusks. Increased fuel costs, additional Greenhouse gas emissions, loss of maneuverability due to hull deterioration, and expensive cleaning procedures all contribute to the negative impacts of biofouling. Manufacturers of antifouling additives and marine antifouling coatings greatly benefit from the ability to quantitatively characterize adhesion and zeta potential in order to optimize these properties for high performance and longevity of antifouling additives.
Instrumented scratch testing is used for determination of adhesion of substrates with surface coatings. The adhesion of the coating is determined via critical loads, which are defined as the load that corresponds to the first appearance of a particular type of failure such as cracks or delamination. Usually several critical loads can be determined: the first cracks in the coating (mainly cohesive damage), partial delamination (adhesive failure), and complete delamination (catastrophic adhesive failure).The scratch test can be used for quality control in addition to research and development purposes.
Zeta potential is a characteristic parameter for describing the surface chemistry of solids, and is located at the interface between a solid and a surrounding liquid. The zeta potential represents the surface charge, which occurs in the presence of an aqueous solution when reactive (functional) groups dissociate on hydrophilic surfaces or water ions adsorb onto hydrophobic surfaces. Varying the pH value of the aqueous phase influences the equilibrium between dissociation and adsorption processes, giving insights into the chemical behavior of the surface.
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