Two Surprises from Inorganic Zinc-rich Silicate Coating

Much of the information we are seeing at this symposium revolves around the utility of Zn rich coatings. Marine Environmental Research (MER) has been examining these coatings as the material component in a surface protective system applicable to both marine and land based needs. The nonmaterial component of this system is electrical. The way these two components interact and the surprising results are addressed in this paper. Pushing an object through a fluid seems a simple enough system to model. It is simple until an attempt is made to do so. Recent Americas Cup races have been decided on the basis of who has the best modeling software. Military and commercial operations spend a great deal of effort approaching this problem. In general, the resistance to pushing objects through water can be treated as having two components: static and frictional. Static resistance is predominantly a function of the shape of the vessel and is most important at higher velocities (surprise). Frictional resistance is determined largely by the “roughness” of the vessel hull surfaces. How important this can be is shown in figure 1. These diagrams show that is possible to quickly require increased fuel burning just to keep the same speed. Since shipping is based on meeting timetables and not consumption tables, biofouling that results in an increased roughness of vessel surfaces is a major concern of marine traders. Power requirements rise, vessel ranges drop and the new limitations hinder commerce and defense. Over the years, methods have been put forth to keep fouling to a minimum. Efforts at keeping the hulls clean include scraping and antifouling coatings. The antifouling coatings have included copper, tar/pitch, coatings with toxic components and coatings that are ablative, hard or slippery(l). Figure 2 shows this schematically. None of the existing systems are suitable for large scale commercial applications for reasons of cost, environmental concern or longevity.