A top coat for a boat is the paint that makes up the final look; aside from adding aesthetic value, the top coat will add protection and durability to the boat’s finish. Surface painting and refinishing of a boat can be a bit complicated.
When choosing top coat paint for a boat, three main components must be considered: the substrate of the boat, the preparation of the substrate and paint products, and the upkeep of the finished product. Each one of these factors will be important in choosing a top coat paint system.
The substrate is the immediate surface material of the boat; the part which will take the top coat of paint. The five types of substrates are fiberglass, aluminum, steel, epoxy, and wood. While any paint system can be used for the former four types of substrates, on wood it is best to stick with a single-part system in order to allow more flexibility and to prevent cracking. The exception to this wood construction rule is if epoxy is used to cover wood—such as with epoxy-coated plywood.
Preparation and Previous Paint Systems
Preparation and any previous paint systems used are also important factors in the new top coat paint choice. A previously painted boat in good condition can have the same paint system as was used before, or can take a one-part paint system if the previous paint system is unknown. If the previous finish is in poor shape, it is best to remove the previous top coat back to its bare substrate and start over.
Use and Upkeep
Different areas of the boat will need different types of top coat. When repainting in an area where there will be a good amount of foot traffic, the hardest finish is recommended. Hardness and abrasion-resistance is important in these areas because people tend to drag heavy items—such as coolers—across the surface.
Top Coat vs. Gelcoat
Gelcoat paint is used when building a boat. Top coat paint is for refinishing a boat. The Gelcoat finish is what would typically be found on a fiberglass boat manufactured in a production line. The material is applied in the mold and then cured. After sufficient aging, top coat painting systems may be applied in order to change the color.
One-Part and Two-Part Paint Systems
A one-part system has just one top coat of paint, but also includes a primer, a filling and fairing compound, and a sealer. Two-part systems contain the same as one-part systems, but the top coat is in two parts: the base component and the curing agent.
While one-part paint systems may be used over one- or two-part paint systems, two-part systems cannot be applied over one-part systems. If the previous top coat paint is in good repair, but the system used is unknown, it is safer to either use a one-part system or strip the surface back to bare substrate.
There are two types of two-part paint systems available. From the automotive industry, there is acrylic polyurethane. From the aviation industry, there is polyester-based polyurethane. The polyester-based paints used in the aviation industry are tougher; they are more resistant to scratching and solvents. Cars simply do not suffer the same rigors during their lifetimes as do aircraft.