Marine Toilet Systems Specialists Show You How to Remove All Those Layers of Bottom Paint

Your Marine Toilet Systems Professionals Know the Frustration of Removing Layers of Bottom Paint 

Raritan Engineering your marine toilet systems experts would like to share with you this week these tips on how to remove many layers of bottom paint.

So, a couple of years back, you acquired a good old boat at a pretty good price—thanks to the market—but now you’re wondering how many coats of bottom paint it has. And what kind? You’ve put on a few coats of ablative antifouling since you’ve owned the boat. It has adhered well and has done its job. But each year, the bottom looks rougher and rougher—with big recesses where paint has flaked off. You sweated out some extra prep-work this season, and thought you had a nice, durable subsurface for painting, but each pass of the roller pulls up more paint. What’s going on here?

More than likely, you probably have too much paint built up on your hull, and this is affecting adhesion. How much is too much? Well, that depends on the type of paint: hard or ablative. With a hard paint, adhesion loss will begin around 20 mils of thickness (approximately 10 coats). Having more layers built up will make the inner layers less flexible and more likely to chip, flake, and lose adhesion. 

Ablative paints will begin to lose adhesion around 15 mils of thickness—but since the coating ablates over time, it should not build up like a hard paint. As you use the boat, the paint should wear away, or ablate, and every time the product ablates, it is releasing fresh biocide. 

Your Marine Toilet Systems Analysts Offer the Best Paint Removal Suggestions For You

If you’ve been applying two coats of ablative each year for the last three years, that’s already six coats of paint for a total of 12 mils, not including the previous applications. Your marine toilet systems specialists know that if you aren’t using the boat often enough, those layers are building up, and a slow-moving sailboat will not ablate at the same rate as a powerboat.

Paint removal options vary, and what’s best will depend on how much old paint there is and your personal preference. If there aren’t that many layers of bottom paint, you can sand them off with an 8-inch, dual-action orbital sander and 60-grit sandpaper, but this is hard work and requires careful safety precautions. Overzealous sanding can lead to dings and divots in the gel coat.

Another option is using a chemical paint stripper like Peel Away or Franmar Soy Strip. Chemical paint strippers break down the paint’s adhesive bond on the hull and make it easier to scrape down to clean substrate that can be repainted. 

Both of these methods will be time-consuming on larger boats. Before tackling this project, check out our October 2011 article, “A Mathematical Decision Maker,” which outlines a formula for determining whether the DIY approach is right for you. 

For owners of older boats with unknown, well-adhered coatings, a tie coat can help make sure successive coatings stick. The major bottom paint manufacturers—Interlux, Pettit, and Sea Hawk—all have priming/tie-coat products. 

How long you wait to strip down the old paint depends on how bad the adhesion issue is and your tolerance for a rough bottom; work boats go years without stripping. Eventually though, adhesion will suffer. 

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via Too Many Layers of Bottom Paint?