How to remove calcium build up from the waterline on my pontoons?

Skipper March 22, 2019 Ask The Skipper

Tabers86 asked:

Like to know what product &or process to use to clean calcium lines& roughtexture lefteven after pressure washing. Calcium lines are thick,hard to scrape off with putty knife. Not a fan of shiny polished look,too bright.if I have to sand & buff to a shine I’ll live, Just like a clean alum look.

Answer:

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The calcium scum line is caused by calcified algae. What you have is limestone or calcite (marble) along your waterline. We’ve been trying for years to come up with a suitable chemical removal, but no luck so far. Anything strong enough to eat the limestone quickly will eat the aluminum first. It’s important to get the limestone off as soon as you can. If you leave it, it will only get worse, more dense and more difficult to remove in the future.

The only solution is to wet sand the stuff off. I suggest using a Linear Buffer with about 600 to 800 grit sandpaper, to mimic the grain in the aluminum. It’s important to sand back and forth with the grain, that’s why the Linear Buffer. If you sand across the grain or in a circular motion you will leave swirl marks that look terrible. If you have heavy growth, you may want to start with a heavier grit, but be careful not to touch the aluminum, otherwise you’ll leave deep scratches that will be hard to remove. The idea is to sand off the limestone not the aluminum. It’s already thin enough.

When you get the limestone off, you can then buff the pontoons, using the same Linear Buffer with the special Alumabuff Buffing Pads and Alumabuff. That will restore the pontoons to a like new finish, not chrome. It will make your boat look sharp and add value to it.

Going forward, you’re going to have the same problem next year and the year after, etc. because of the minerals and the species of algae in the water. I suggest that you protect the pontoons to mitigate the problem. After restoring the pontoons, you can protect the aluminum with Alumetron. That will keep them looking new and eliminate the water staining and streaks etc. After apply VS721 to the entire pontoon. It’s a low surface energy fouling release coating that will make clean up much easier as it can withstand cleaning with strong acids without damaging the aluminum. If, during the season, you wipe the slime off the pontoons as it appears, you won’t get any growth at all.

The reason for owing a boat is to enjoy boating, not making more work for yourself. Protecting the boat surfaces properly at the beginning of the season will allow you to spend more time with your friends and family and less time on your back under the pontoons. If you neglect the maintenance, the problem will only get worse until you have a failure. Marine growth on the bottom of your pontoons only increase fuel burn, encourages more growth and slows the boat. Because of the design of pontoon boats the effects are dramatic.

Thanks for your question,

Captain Aurora
Richard Kittar