Coppercoat bottom coating is epoxy with copper suspended in it. Burnished to a smooth, hard finish, it can last for years before needing reapplication.

Choosing a bottom paint for a boat depends on many factors including where the boat sails—some copper biocides are outlawed for use in certain locations—the kind of sailing the boat does, the boat’s construction, the amount of maintenance an owner is comfortable with and ease of application.

Ablative paints, such as VC17m and Interlux Micron Extra, are relatively soft paints that include a biocide to retard organic growth and are the most commonly used type of paint. The ablative property of the paint means that it wears away as water flows over it. This wear prevents excessive paint build-up and, more importantly, continually exposes fresh biocide to prevent future growth.

Other bottom coatings incorporate different technologies. Coppercoat, for example, is a layer of epoxy with pure copper powder suspended within it. Once immersed, seawater begins to corrode the copper particles, resulting in the formation of cuprous oxide, a highly effective biocide. In time, the cuprous oxide converts to cupric hydrochloride and sloughs off in the water. The sloughing exposes fresh copper, and the process repeats. Coppercoat is burnished to a hard, smooth finish after application,  and the smooth surface combined with the biocide action makes for an effective antifouling surface. --B.P.