Painting a boat can be a big project, and choosing the right type of paint is an important decision. Many boat owners consider using automotive paint because it is readily available and often less expensive than marine paint. However, there are some important differences between automotive and marine coatings that need to be considered before using car paint on a boat. This article will examine the key factors in deciding whether automotive paints are suitable for marine use.
Differences Between Automotive and Marine Paint
Automotive and marine paints are formulated differently to meet the needs of their particular operating environments. Here are some of the key differences:
Durability
Marine paints are designed to withstand prolonged exposure to water, salt spray, and ultraviolet rays from sunlight. Automotive paints do not hold up as well over time when subjected to these marine conditions. The binders and pigments in marine coatings provide longer lasting protection.
Flexibility
Boats frequently flex and bend while underway. Marine paints maintain their integrity when the substrate flexes. Automotive paints are more likely to crack or peel when flexed repeatedly.
Slickness
The smooth finish of marine paints allows water to sheet off and minimize drag. Automotive paints have more texture which can increase friction.
Single Part vs Two Part Paint
Many marine paints are two part coatings that cure by a chemical reaction when the base and catalyst are mixed. Automotive paints are typically single part coatings that rely mainly on evaporation for curing. Two part marine paints generally provide tougher, longer lasting protection.
Toxicity
Some states prohibit the use of automotive paints on boats because they contain high levels of volatile organic compounds (VOCs). Marine paints meet stricter VOC regulations to minimize environmental and health hazards.
When Automotive Paint Works on Boats
While marine grade coatings are always the best choice for prolonged water exposure, there are some situations where automotive paints can work successfully on boats:
Small Craft
Using automotive paint on very small boats that are lightly used, such as dinghies, canoes, kayaks, or other non-motorized craft, is often acceptable. The flexing forces and exposure to abrasion and moisture are much lower than on larger vessels.
Above The Waterline
Applying automotive paint only above the waterline reduces moisture exposure and flexing compared to below the waterline areas. Touch ups and repairs to the topsides of cabin cruisers or sailboats can utilize automotive paints.
Fresh Water Use
In fresh water environments, automotive paints hold up better over time than in salt water conditions. Using them on boats that operate exclusively in lakes or rivers increases the chances of success.
Interior Surfaces
For interior surfaces not exposed to moisture, like cabinets, floors and furniture, automotive paint can provide good results on boats. Gloss and color retention are less impacted.
Temporary Paint Jobs
If repainting the boat annually, automotive paint may be adequate. The lower durability is less of a factor if not trying to achieve multi-year protection.
Preparation for Painting
The key to success when using any boat paint, automotive or marine, is proper surface preparation. Here are some tips for getting ready to paint a boat:
– Remove all prior coatings completely – take the surface down to bare substrate if possible.
– Sand smooth any remaining paint or gelcoat. Feather out rough edges or flaws.
– Clean thoroughly to remove sanding dust, oil, grease and other contaminants. A detergent wash and fresh water rinse should be done.
– In fiberglass or wood boats, seal any exposed pores with a fiberglass resin or wood sealer before painting.
– Use an appropriate primer for the substrate you are painting. Seal bare metal with a zinc chromate or etching primer first.
– Abrade each primer coat before applying the next layer of coating for better adhesion.
– Follow all safety precautions when sanding or spraying paints. Use protective gear and ventilate enclosed spaces.
Proper surface prep provides a clean foundation for the paint to adhere to. This helps maximize the durability and longevity of the finish.
Applying Automotive Paint on Boats
When using automotive paints on a boat, pay close attention to application techniques for best results:
– Carefully follow the manufacturer’s mixing and thinning instructions. A paint thinner suited for marine use is preferable over automotive thinner.
– Apply using multiple thin coats, allowing proper drying time between coats. Thicker coats are more prone to runs, drips or solvent entrapment.
– Maintain a wet edge during application to prevent lap marks and vary your starting points. Consistent overlap of the spray pattern is key.
– Hang large pieces to paint separately if possible. This allows for all around application and avoids drips.
– Maintain uniform spray distance and avoid arcing motions. Keep the gun perpendicular to the surface.
– Use a 50% overlap with each pass of the spray gun to ensure even coverage.
– Apply coats in quick succession before earlier coats fully cure to enhance bonding between layers.
– Allow paint to fully cure before launching boat. Check manufacturer’s recommended cure times.
Proper spray technique provides the smoothest, most uniform finish using automotive paints. This gives the coating the best chance of withstanding the marine environment.
Maintenance Tips
To maximize the lifespan of automotive paint on a boat, here are some useful maintenance tips:
– Wash frequently using a boat soap and non-abrasive cloth, sponge or brush. Salt, grime and pollutants can be corrosive if left on the paint.
– Rinse well with fresh water after each use. Saltwater and contaminants adhere to wet paint so thorough rinsing helps neutralize this.
– Apply a marine grade wax two or three times per year. The wax provides added protection from UV rays and water intrusion.
– Touch up any scratches or nicks in the paint quickly to prevent corrosion. Keep automotive paint in matching colors on hand for touch ups.
– Check for any cracking or peeling paint each season. Sand and spot paint as needed before those areas spread.
– Avoid harsh cleaners or chemicals which can degrade the paint prematurely. Do not use abrasive pads.
– Store under a cover or out of direct sunlight when not in use to minimize UV exposure.
Staying vigilant with regular cleaning, waxing, inspection and touch ups enables automotive paint to last longer in the harsh marine environment. But for a worry-free, long-lasting finish, marine grade coatings are the best choice.
Conclusion
While automotive paints are not formulated to withstand all marine conditions, they can be effective on boats in certain situations. Small craft, fresh water use, interior areas, and above water applications provide some opportunities for success. However, for prolonged water exposure and larger vessels, a marine grade coating will always provide superior performance and durability. If choosing to use automotive paint on a boat, proper preparation and application are crucial to maximize coating life. Ongoing maintenance and vigilance in checking for early signs of breakdown can help extend the finish. But for the toughest, longest-lasting protection, a high quality marine enamel, polyurethane, or epoxy coating is a boat’s best defense against the elements.
